Fundamental Og Well Built SAN-4AA2-5616ENW

8/6/2019 Fundamental Og Well Built SAN-4AA2-5616ENW

1/15

Fundamentals of a W ell-Built SAN

W hite paper

Table of contents

Introduction..................... .................. .................. .................. .................. .................. ................ .......... 2Executive summary................. .................. .................. .................. .................. .................. .................. .. 2Anatomy of a SAN ................ .................. .................. .................. .................. .................. .................. .. 3The advantages of iSCSI SANs ................. .................. .................. .................. ................. .................. ... 3Core features of HP LeftHand SANs................. .................. .................. ................. .................. ............... 3

True clustering ................ .................. .................. .................. .................. .................. .................. ..... 4Storage virtualization .................. .................. .................. .................. .................. .................. ........... 4Reliability with Network RAID............. .................. .................. ................. .................. .................. ...... 5Continuous data availability...... .................. .................. .................. .................. .................. .............. 5Scalable capacity and performance.......... ................. .................. .................. .................. .................. 5Easing administration overhead................ .................. ................. .................. .................. .................. 5Enhanced data services...... .................. .................. .................. .................. .................. .................. .. 5HP Services................. .................. .................. .................. .................. .................. .................. ........ 5

Scalable performance .................. .................. .................. .................. .................. .................. .............. 6Scalability by design ................ .................. .................. .................. .................. .................. .............. 6Limitations of traditional architectures..... .................. ................. .................. .................. .................. ... 6Objective scalability measures........................... .................. .................. .................. ................. ......... 7Flexible scalability models.................. .................. .................. .................. .................. .................. ..... 8Scaling with tiered storage........ .................. .................. .................. .................. ................. ............... 8

High availability..... .................. .................. .................. .................. .................. .................. ................ . 9Synchronous replication and disaster recovery with multi-site SANs........ ..... .... ..... .... ..... .... ..... .... ..... .... ... 9

Reliability by design...... .................. .................. .................. .................. .................. .................. ......... 10 Building reliability from the ground up ............... .................. .................. .................. .................. ....... 11

Extreme performance................ .................. .................. .................. .................. .................. ............... 13 Performance through parallelism...... .................. .................. .................. ................. .................. ....... 13 Increasing parallelism and performance with MPIO DSM .................. .................. .................. ............. 13 Increasing bandwidth dramatically........................ .................. .................. ................. .................. .... 14 Investment protection ................ .................. .................. .................. .................. .................. ............ 15

Conclusion............. .................. .................. .................. .................. .................. .................. ............... 15 For more information.......................... .................. .................. .................. .................. .................. ...... 15


2/15

Introduction

Next to its people, data is a companys most valuable asset. Businesses of every size rely heavily on

data that is at once increasingly complex and increasingly regulated. In countries around the world,

government regulations dictate how financial, customer, personnel, and health-related information is

stored, maintained, and retained.

Central data storage and management help organizations achieve compliance with this mountain of

requirements, and help enable business-critical data to be available when users need it. Storage areanetworks, or SAN s, are common solutions for businesses seeking to simplify storage. Unlike direct

attach storage (DAS), which creates disparate, random islands of information, SAN s centralize data

storage. Disaster recovery solutionsa necessity in todays worldare easier to implement on SAN s,

and the stored data is easier to manage than in a DAS environment.

A company that leverages server virtualization for high availability and disaster recovery has even

more reason to deploy a SAN and not just any SAN . Virtualized environments need shared storage

to take full advantage of the shared infrastructure. W hen both server and storage are protected, the

solution is complete.

Although Fibre Channel SANs are an option for large enterprises, these storage solutions tend to be

expensive and limited in their flexibi lity. Compact and cost-effective, iSCSI SAN s are a better fit for

many businesses. HP LeftHand iSCSI SAN solutions are built in a fundamentally different way. Built

from the ground up to be flexible, scalable, and highly avai lable, HP LeftHand P4000 SANs deliver

all of the features of enterprise storage and are an excellent fit for disaster recovery, business

continuity, and virtualized storage solutions.

Executive summary

Your businesss increasing reliance on data calls for a well-designed and well-built data storage

system. Agile, easy to deploy, and intuitive to manage, HP LeftHand P4000 SAN Solutions provide

all of the functions that organizations expect to see in a Fibre Channel SANat an affordable price

point that makes centralized storage an economical option even for small- and medium-sized

businesses. In fact, HP LeftHand SANs enable high avai lability and lower cost 49% in small sites and

remote offices by turning internal server drives into shared storage1 . And, because HP LeftHand SANs

are built with a superior architecture, they are more scalable and offer higher availability, more

reliability, and higher performance than other iSCSI SAN products.

HP LeftHand SAN s are based on iSCSI technologySCSI over standard Internet protocols (IP). This

allows companies to use the standard iSCSI drivers that accompany server operating systems to

access storage over standard IP networks.

HP LeftHand SANs use a process called true clustering. True clustering means that every storage

system in a cluster participates equally in sharing both the clusters workload and storage capacity.

The cluster manages itself. W ith true clustering, organizations can administer a single entity while

configuring virtual volumes and per-volume Network RAID levels. They can also take snapshots, makeremote copies, scale the cluster, and even take storage systems down for upgrades or maintenance

all without affecting data availability.

HP LeftHand SANs deliver the enterprise storage management features that companies expect of Fibre

Channel SANs. However, the similari ty ends there. The purpose of this white paper is to describe the

benefits of a clustered architecture in comparison with traditional controller-based architectures, and

to discuss the technology that makes HP LeftHand SAN s better by design.

1 Based on US list price comparison on July 1st, 2009 between a 4TB dual-controller Dell EqualLogic PS6000 and HP P4000 VSA Software plus

24 250GB HDDs used to create the virtual iSCSI SAN in a VMware deployment.

2


3/15

Anatomy of a SAN

Every SAN is deployed using a combination of software, hardware, and services. In this respect,

HP LeftHand SANs are no different from any other SAN . W hat make them different are the

advantages they provide in all three of these areas. HP LeftHand SAN s run powerful HP SAN / iQ

software, clustering multiple storage systems into a single SAN that you can manage from a central

console. They operate on enterprise-class, industry-standard, x86-architecture-based hardware

equipped with advanced disk drives, processing elements, caches, and controllers. Finally, HP

provides support and service that keeps customer data available and protects it from loss.

The advantages of iSCSI SANs

As they evaluate technologies, many organizations choose iSCSI SAN s because of the complexity

and costs of tradi tional Fibre Channel (FC) SAN s. Installing a traditional FC SAN means purchasing

storage hardware years ahead of the need. This costly, buy high, sell low proposition is ampli fied

by ever-plummeting storage costs. The cost of a pair of redundant FC host bus adapters (HBAs), which

can approach that of a small server, impedes the use of centralized storage for all servers.

Growing a Fibre Channel SAN that uses the traditional model of a hardware RAID controller

connected to multiple disk trays has its limits: as the number of disk trays increases, the controller itselfbecomes a bottleneck, requiring the purchase of more complete storage systems. And as 2Gb/ s to

4Gb/ s FC throughput is eclipsed by off-the-shelf 10Gb/ s Ethernet (10GbE), the perception that a FC

fabric delivers better performance than iSCSI is fast becoming obsolete.

Core features of HP LeftHand SANs

HP LeftHand SAN s aggregate the resources of a set of enterprise-class storage systems into a storage

cluster. The result is flexible, scalable, virtualized storage (see Figure 1). The benefits of this

technology are discussed in the following sections.

3


4/15

Figure 1: HP LeftHand P4000 SAN s are comprised of enterprise-class storage systems. The physical blocks in the SAN

corresponding to virtual volumesare distributed evenly across the cluster.

True clustering

P4000 SAN s provide true, n-way clustered storage, not a traditional two-way active/ active or

active/ standby configuration. True clustered storage means that a set of storage systems is managed

and scaled as a single entity, with all of the clusters resources available to respond to requests. As

the cluster is expanded, the resources available to handle requests increase as wellalleviating the

problem of a controller bottleneck, which is commonplace when traditional SANs are scaled.

Storage virtualization

True clustering creates a virtual pool of storage, spreading the storage for its virtual volumes evenly

across all storage systems in the cluster. Storage can be reserved at the time that the virtual volumes are

createdor, through thin provisioning, it can be allocated only as disk blocks are actually needed.

HP LeftHand SANs virtualize every volume across all the storage systems in a clusternot within each

storage system, as do traditional Fibre Channel SANs. The sharing of storage across the entire clusterresults helps increase performance and storage utilization; in addition, it helps decrease management

costs and complexities as clusters are scaled.

4


5/15

Reliability with Network RAID

The reliability of HP LeftHand SANs begins with RAID storage on each storage system. It is then

enhanced wi th Network RAID, which replicates each block across the storage cluster up to four times.

W hen a virtual volume is populated, i ts data blocks are striped and replicated across the clusters

storage systems so that the entire cluster participates in the storage of every virtual volume.

Continuous data availability

Network RAID contributes to high availability, helping to ensure that the loss of a single storage

system does not result in data loss. If a server fails to the point where it must be taken offline for

repair, N etwork RAID keeps the single server failure from resulting in loss of data avai lability. W hen

the server is replaced, or repaired and brought back online, the SAN automatically brings the storage

systems data blocks up to date with the rest of the cluster.

The more storage systems there are in a cluster, the less the failure of a single storage system can

affect performance. A traditional active/ active dual-controller SAN product can suffer a 50%

performance decrease in the event of a controller loss. W ith P4000 SAN s, the failure of a storage

system affects performance by, at most, a percentage equal to the proportion of the cluster that the

storage system represents.

Scalable capacity and performance

As a cluster becomes full, storage capacity can be increased by adding storage systems. True

clustering enables considerable scalabi lity. As new storage systems are configured, the cluster

automatically readjusts its block allocation so that the allocated storage and the workload are once

again distributed across the cluster. This procedure immediately scales the clusters performance by

bringing incremental network CPU, memory, cache, RAID controller, and disk resources to the cluster.

Easing administration overhead

All storage clusters are managed through a single, intuitive centralized management console (CMC).

The ability to treat a storage cluster as a single entityrather than a set of discrete storage devices

eases administration costs and changes the cost model from one in which storage must be plannedand purchased upfront to one in which it can be purchased as needed.

Enhanced data services

In traditional SAN s, enhanced data services are typically add-on features. W ith HP LeftHand SANs,

enhanced data services are included at no additional charge. Synchronous replication keeps data

highly available within a cluster, even if that cluster is geographically separated between sites in a

LAN or MAN . Remote copy provides disaster recovery for multiple clusters and sites from a single

interface, and failover and failback are automated features. The unique allocate-on-write thin

provisioning provides the ability to create volumes without dedicating physical storage to them.

Snapshots are space-efficient because they are thinly provisioned.

HP Services

HP LeftHand SAN s are supported by global, world-class enterprise-support services. This can be a

significant advantage for data centers already engaged with HP. Companies may already have

spares on site, they may already know their support technician, and the technician may already be

badged for the site and familiar with its best practices. The size and skill set of the available

hardware support from HP also helps organizations compete.

5


6/15

Scalable performance

Scalability means that adding more resources to a system results in a commensurate increase in the

systems ability to perform work. HP LeftHand SANs use true clustering to deliver a SAN that scales both

storage capacity and performance in a linear manner. Scaling a cluster with additional storage systems

supports growth by scaling existing volumes, adding new volumes, and supporting more servers (Figure 2).

Scalability by design

HP LeftHand SANs are designed to deliver massive scalabi lity. Unlike other clustered storage

products, P4000 SAN s have no bui lt-in limit on the number of storage systems per cluster. Because

true clustering allows them to scale performance and capacity linearly, HP LeftHand SANs differ from

traditional Fibre Channel SAN products.

HP LeftHand SAN s are based on HP ProLiant servers, each of which has its own disk drives, RAID controller,

cache, memory, CPU, and networking resources. Thus, each time a new storage system is added to a cluster,

the clusters processing capacity increases in lock step with its storage capacity. The SANs linear scalability

derives from the fact that the ratio of processing resources to disk storage is constant.

Figure 2: HP LeftHand SANs use true clustering to deliver linear scalability that can support more storage capacity and

performance as the cluster grows.

Limitations of traditional architectures

Compare this scalabili ty model to the traditional controller/ disk tray architecture that is behind most Fibre

Channel SANs and some NAS appliances (Figure 3). These systems use either an active/ active or an

active/ standby pair of processors, and scalability is achieved by adding more disk trays to the

configuration, as more capacity is needed. Using this model, the ratio of processing power to disk

capacity decreases each time a new disk tray is added to the configuration. This causes performance to

increase to the point where the controllers and the Fibre Channel interconnect become a bottleneck;

performance then levels off or even declines. At that point, customers must either upgrade to higher-power

controllers or add new storage systems. Either action can result in significant amounts of downtime.

6


7/15

Figure 3: A traditional SAN architecture scales by adding more disk trays to the configuration.

Objective scalability measures

ESG Lab, part of the Enterprise Strategy Group, measured scalability of HP LeftHand SANs of varying

sizes, and summarized the results in a July 2007 report2 . The test cluster consisted of an HP LeftHand

SAN configured wi th up to 30 HP ProLiant DL320 Servers. Each server was configured with 12

300GB, 15k rpm serial-attached SCSI (SAS) drives, yielding a total of 3.6TB of storage per server.

ESG used the IOMeter benchmark to drive a simulated online transaction processing workload

consisting of 60% read and 40% write operations, using 8KB blocks. Scalability was nearly linear

from five to 30 storage systems, and the 30-server, 108TB cluster was able to sustain almost 50,000

input/ output operations per second (IOPS).

HP LeftHand SANs allow organizations to build clusters whose characteristics are tuned for the

applications they support, scaling each cluster as needed. Many organizations deploy their first

open iSCSI SAN to support specific applications such as Microsoft Exchange Server, VMware

Infrastructure 3, Microsoft SQL Server, and network file sharing. As they begin to see the benefits ofHP LeftHand technology first hand, they scale their cluster to support more and more applications

(Figure 4). As these applications become more diverse in their storage requirements, it often makes

sense to create a new cluster with a different type of storage system as its basis. Both clusters can

scale independently, and logical volumes can be moved between clusters with no interruption in

service. This makes scaling with tiered storage easy and straightforward.

2 LeftHand N etworks 100 TB Enterprise SAN.

7


8/15

Figure 4: Network RAID level 1 stripes and replicates a logical volumes data across the cluster.

Flexible scalability models

HP LeftHand SANs scale capacity as well as performance. Organizations can increase the storage

capacity of a cluster by adding new storage systems, and they can even scale clusters with non-

identical storage systems. Scaling a cluster to 100 storage systems is as simple as scaling to two. In

addition to scaling the size of a cluster, companies can create multiple clusters because the cluster is

managed as a single unit.

Multiple SANs are configured in a single management group by the centralized management console

(CMC), which provides a single, intuitive graphical user interface (GUI) to manage them. Logical

volumes can be copied between clusters with a simple click of the mouse. Given the fact that

management groups can span geographical distances, remote copy works as simply and easily as a

local copy does between clusters.

Scaling with tiered storage

Different types of disk drives have di fferent performance characteristics, and these characteristics

affect storage system performance and thus overall SAN performance. SAS and SCSI drives tend to

have high rotational speeds and low seek times, resulting in low I/ O latency and therefore high

input/ output operations per second (IOPS). Storage systems using SAS drives excel in supporting

transactional applications such as databases and Microsoft Exchange servers. Serial ATA (SATA)

drives tend to have lower rotational speeds and higher latency, but much higher capacity for the price

than SAS and SCSI drives. Clusters built around these storage systems are more cost-effective for

applications that demand high capacity, such as streaming media and general file storage.

8


9/15

High availability

Availabili ty is about keeping data online and available at all times, an attribute that is typically

attempted by using redundant components. But what happens if multiple components fail within a

unit, or the entire unit becomes unavailable?

The HP LeftHand P4000 SAN has redundant components such as redundant power supplies and

hardware RAID 5, 6, and 10. But, to achieve true high availability, volumes must remain online

whether a drive fails or the entire unit becomes unavailable. Network RAID provides this capability atno extra charge.

Network RAID levels are assigned on a per-volume basis so that avai lability can be configured based

on the needs of individual applications and their data. This allows organizations to incur the cost of

redundant storage only for logical volumes that require it.

HP LeftHand SANs support striping plus Network RAID replication levels 0, 2, 3, and 4, which

correspond to replicating each block up to four times. The most commonly configured Network RAID

level, level 2, stripes and replicates blocks so that two copies of each block reside on the cluster

(Figure 4). Using this configuration, the logical volume continues to be available despite the failure of

a single storage system or the failure of two non-consecutive storage systems. Compare this to

products that stripe without replication: the more storage systems in a cluster, the lower the

availabilityand the loss of a single storage system means that all storage is lost.

In HP LeftHand SANs, clusters manage data layout and replication themselves so that failover is

automatic and so is failback. If a storage system fails and is later brought back online, the cluster

manages the process of restoring the repaired servers data to the current level. Likewise, N etwork

RAID level is a property of a logical volume that can be changed at any time. If the level is changed,

the cluster manages the process of increasing or reducing the replication level of data for the logical

volume as required.

Synchronous replication and disaster recovery with multi-site SAN s

The availability properties of Network RAID mean that functionality such as synchronous replication

and disaster recovery is built into the solution. This simplifies administration, helps to protect data, andreduces costs compared to tradi tional SAN s.

Volumes stored with Network RAID level 2 have blocks striped across every other storage system, with

replicas stored across the rest. Logical volumes continue to be available even if half the systems in the

cluster fail.

Synchronous replication to provide multi-site high availability can be implemented simply by placing

half the storage systems in one location and the rest in another. W hether the alternate location is a

different closet in the same building, another building on the same campus, or a data center far

away, blocks are synchronously replicated across the two sites, and an entire site can fail without

making any data unavailable (Figure 5).

W hen the failed site comes back online, its storage systems automatically obtain any changed blocks

so that failback is automatic and transparent. With traditional SANs, this process can be time-

consuming and error-prone, and it can require application downtime.

9


10/15

Figure 5: Placing alternate storage systems in different, alternate locations enables synchronous replication and disaster

recovery as natural side effects of HP LeftHand SAN storage.

Reliability by design

Reliability is about protecting against data loss, which is a considerable proposition given the forward

march of disk technology. Disk reliability is typically expressed in terms of bit error rate (BER), which

means that disks may fail as a function of the amount of data read or written. As disk technology

allows drives to contain more data, they are more likely to fail when read from beginning to end; this

is exactly what happens during a RAID array rebuild after a single-disk failure.

The upward trend in disk sizes means that the dreaded second-disk fai lure that incapacitates a RAID 5

array is becoming more likely as disk sizes increase. Indeed, the chance of a second disk failure

while rebuilding a 9TB RAID array of SATA disk drives is nearly 10%greater than the probability of

a dual controller failure in a traditional SAN . RAID 5 by i tself is no longer sufficient. The reliabili ty by

design of the HP LeftHand SAN allows organizations to configure logical volumes and clusters to

provide higher reliabili ty levels.

10


11/15

Building reliability from the ground up

Reliability is built into every HP LeftHand SAN, from the choice of storage systems to the additional

features that help organizations better manage their data.

Hardware features: Every component in an HP LeftHand SAN includes dual power supplies, network

interface cards (NICs), environmental monitoring, and a battery-backed-up write cache.

Choice of drives: The HP LeftHand SAN offers storage options that allow customers to choose the

combination of performance, capacity, and reliability that best suits their applications. Enterprise-class

SAS and SATA drives offer reliability levels equivalent to the Fibre Channel drives found in traditional

SAN s, with a BER of 1/ 1016. W here capacity and price are more important than this level of

reliabi lity, SATA drives can deliver a BER of 1/ 1014.

Hardware and Network RAID: Each storage system has built-in hardware RAID and battery-backed-up

write cache, both of which contribute to reliability and data protection. Depending on the system and

customer requirements, hardware RAID levels 5, 6, and10 can be configured on each storage system

and then combined with Network RAID levels to maximize availability.

Proactive self-healing: Just like traditional Fibre Channel SAN s, HP LeftHand SANs monitor storage

systems for marginal environmental or drive condi tions, allowing an HP LeftHand SAN to respond

with proactive support services, repairing potential faults before they result in an actual failure. Each

storage system is constantly scrubbing its storage to re-map bad blocks and restore data from astorage system that has an intact replica.

Geographic failover: Many organizations view the potential loss of data and application downtime

due to the failure of an entire data center as unacceptable. Network RAID allows for synchronous

replication and geographic failover so that business can continue without interruption. As discussed in

the Synchronous replication and disaster recovery with multi-site SANs section, synchronous

replication is integrated into the superior architecture of HP LeftHand SANs. W hats more,

organizations can purchase an HP P4300 SAS Starter SAN for the price that some vendors charge

for their remote replication software alone. And, unlike the competitions remote replication software,

failover and failback are not applicable to a HP LeftHand SAN because storage volumes remain

online and accessible throughout a site failure.

Space-efficient snapshots: Every organization knows that there is no substitute for stable, offline tapebackups. HP LeftHand SAN s support space-efficient snapshots where only the metadatanot the

blocks themselvesis copied to create the snapshot. Space efficiency means that the storage system

does not have to reserve an amount of storage for the snapshot equivalent to the size of the volume

itself. Space efficiency results in significant savings compared to traditional SAN s.

Scheduled snapshots can be coordinated wi th application software so that the snapshot represents a

stable point-in-time copy of application data. In contrast to traditional SAN s, snapshots in HP LeftHand

SANs can be mounted and written to by the backup software.

Snapshots may also be created manually and used to create temporary environments for developers

and administrators. Software upgrades and patches, for example, can be applied and tested to a

volume snapshot and tested on a real server or in a virtual machine before they are put into

production. Costs for these snapshots are low because an equal amount of additional storage does

not have to be available in order for the snapshot to be taken.

Remote copy and asynchronous replication: The snapshot mechanism in an HP LeftHand SAN forms

the basis for remote copy and asynchronous replication capabilities. Snapshots contain an identifier

that ensures uniqueness within a management group. Snapshots can be copied between clusters,

promoted to be actual volumes, and then mounted and used. W hen clusters are geographically

separated, a local copy becomes a remote copythere is no difference.

11


12/15

Consider an organization with data centers in Seattle and San Francisco, with New York acting as a

central data repository for backups or as a disaster recovery site (Figure 6). Snapshots can be created

in Seattle and San Francisco, copied to New York, and then promoted to be fully populated volumes.

Servers C and D, the users of the promoted snapshots, could represent hot standby servers for

disaster-recovery purposes, or they could be used to handle tape backup of the copied volumes.

Figure 6: Remote copy is based on the snapshot mechanism, and it can be used for disaster-recovery and

remote-archiving purposes.

HP LeftHand SANs support scheduled snapshots and remote copies. Used in combination, these two

capabilities provide asynchronous replication, where batches of data representing the difference

between two snapshots are created and transferred between sites on a periodic basis.

Reliability is about protecting against data loss every step of the way, from establishing a per-server

reliabi lity baseline to supporting geographic fai lover and failback capabi lities. HP LeftHand SANs

provide flexible reliability at a price point that makes them superior to traditional SANs.

12


13/15

Extreme performance

The disk spindles performance characteristics ultimately drive disk storage system performance. O ne

challenge facing vendors of storage systems is how to extract the most performance from them.

In contrast with traditional SAN s, HP LeftHand SANs excel at extracting top performance from storage

systems. Companies that use HP LeftHand SANs experience the high performance and capacity of the

latest disk drivesstandard in the HP ProLiant servers on which LeftHand SAN s are basedlong before

those drives are avai lable in traditional SAN architectures. In addition, HP LeftHand SANs leverage theunderlying hardware to extract an uncommon level of performance from the hardware itself.

Performance through parallelism

Most SAN s increase storage system performance through parallelism. HP LeftHand SAN s allow

organizations to tune the level of parallel operations in their cluster to achieve required

performance levels.

Performance begins with RAID storage on each storage system, which uses parallel disk operations to

deliver high I/ O bandwidth. Even though RAID 5 is the default configuration, higher and lower RAID

levels can be configured to adjust both performance and protection. For example, RAID 10 can be

configured for higher performance requirements, and RAID 6 can be configured to protect against

multiple drive failures.

A level above RAID on the individual storage systems, the cluster itself contributes to performance by

striping dataregardless of N etwork RAID levelacross the entire cluster. Just as RAID on the storage

systems delivers the performance of disk drives working in parallel, Network RAID on the cluster itself

delivers the performance of multiple RAID arrays delivering data in parallel. Striping across multiple

storage systems is managed by the cluster itself, so administrators can manage only a single entity

rather than a set of individual storage systems.

Compared to tradi tional SAN s, where the controllers themselves become a bottleneck as more disk

trays are added to a system, HP LeftHand SAN performance grows as storage capacity grows. This is

because each time a new set of disks are added to the cluster, they are supported by an additional

set of resources, including: CPU and main memory for managing storage, I/ O, and the cluster Hardware RAID controller per storage system Additional battery-backed-up storage for each storage system Additional network interfaces that can operate in parallelIncreasing parallelism and performance with MPIO DSM

By default, an HP LeftHand SAN load-balances initial login requests from client iSCSI drivers across

the storage system, and then processes all subsequent requests from that client through a single

storage system. The storage system redirects each client request to the server owning the desired

block, and then redirects the response back to the client. Although this approach results in excellentscalability, it is not as scalable as the performance that can be achieved with the HP LeftHand device-

specific module (DSM) for the Microsoft Windows Multipath I/ O (MPIO) iSCSI driver.

The MPIO DSM contains intelligence on the layout algorithms for the storage cluster. It can thus

calculate the location of any block in any virtual volume. Knowing which server contains the desired

block allows the iSCSI driver to contact the storage system that owns the block directly, without the

redirection used by the standard load-balancing approach. Figure 7 illustrates a redirected login

sequence, the SCSI mode sense command that loads the cluster-specific information into the driver,

and the separate I/ O path that the driver establishes to each server in the cluster.

13


14/15

Figure 7: The HP LeftHand SANs device-specific module for the M icrosoft MPIO driver (MPIO DSM) increases performance by

establishing parallel I/ O pathsone to each storage system in the cluster.

The MPIO DSM provides the most benefit wi th sequential I/ O. Performance scalability for standard

load balancing is excellent. However, as the volume of data increases, the load that redirection

imposes on the network increases as well. MPIO DSM eliminates the additional data movement and

allows data to stream directly from storage systems to the client systems. W here the benefits of larger

clusters for standard load balancing begin to diminish, the MPIO DSM configuration allows

performance to continue to climb significantly higher as storage systems are added to the cluster.

Increasing bandwidth dramatically

Most storage systems are limited in bandwidth. In traditional SANs, once storage capacity is

increased to the point where the systems controllers can no longer provide increased bandwidth

along with increased capacity, customers either must upgrade controllers or purchase additional

storage systems. Multiple traditional storage systems add not only cost but also complexity. They also

need to be managed individually with volumes statically allocated to each system, resulting in

fragmentation. In contrast, a storage cluster can virtualize storage across the entire system.

14


15/15

Investment protection

The industry standard, enterprise-class x86-architecture in an HP P4000 SAN offers unprecedented

investment protection for organizations. For example, they can repurpose existing storage servers as

application servers and, using the HP P4000 Virtual SAN Appliance (VSA) Software, provide SAN

storage on them as well. In small sites and remote offices, HP LeftHand SANs enable high availabi lity

and lower costs 49% by turning internal server drives into shared storage.

Investments in HP LeftHand SAN s continue to be protected through the transition to 10 -Gb/ s Ethernet

(10GbE). Customers can upgrade existing clusters in the field with standard 10GbE interfaces andconnect to standard PCI Express peripherals. Redundancy built into the underlying platform allows

them to upgrade to a live cluster without impacting data availability.

Unlike traditional SANs, each storage system in a cluster contributes to performance by delivering

data in parallel. So deploying a cluster with 10GbE provides improved throughput, which is then

enhanced further when that throughput is multiplied by the number of storage systems in the cluster.

Conclusion

Every SAN is built from a combination of software, hardware, and services, and in this respect iSCSI

SAN s from HP are no different from any other SAN . But that is where the similarity ends. HP LeftHand

SANs use distributed, clustered technology to deliver all of the functionality expected of a storage

area network. They add the advantage of l inear scalabili ty, high availabili ty, per-logical-volume

configured reliability, and throughput of 10-Gb/ s per node that is aggregated between all nodes in a

cluster. Better by design, HP LeftHand P4000 SANs deliver functionality including synchronous

replication, asynchronous replication, and remote copy. These are built-in features of a superior

architecturenot an add-on option that can cost as much as an entire SAN.

W ith true clustering, HP LeftHand SANs can virtualize storage across all storage systems in a cluster

and even between clusters in the same management group. True clustering allows organizations to treat

a cluster as a single entity whose resources can be scaled and configured as needed. This helps deliver

the unique combination of performance and reliability that each application in a data center requires.

For more information

For more information on HP LeftHand iSCSI SAN s, visit www.hp.com/ go/ P4000.

Technology for better business outcomes

Copyright 2009 Hewlett-Packard Development Company, L.P. The informationcontained herein is subject to change without notice. The only warranties for HPproducts and services are set forth in the express warranty statementsaccompanying such products and services. Nothing herein should be construed asconstituting an additional warranty. HP shall not be liable for technical or editorialerrors or omissions contained herein.

Microsoft and W indows are U.S. registered trademarks of Microsoft Corporation.
http://www.hp.com/go/P4000http://www.hp.com/go/P4000http://www.hp.com/go/getconnected

Documents

Fundamental Og Well Built SAN-4AA2-5616ENW