EGL2 Dell Compellent Storage Center-11

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Dell Compellent Storage Center - Product Analysis

Evaluator Series Research - October 26, 2015

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2015 Evaluator Group, Inc. All rights reserved. Reproduction of this publication in any form without prior written permission is prohibited.

Dell Compellent Storage Center

The Dell Compellent Storage Center is a block storage system aimed at the mid-tier enterprise market. Thelargest models are the SC9000 and the earlier SC8000. A scaled down version is offered as the SC4000, targeted

at more cost competitive markets and the SCv2000 has three models in the family as economical entry level

systems. Dell calls their design Fluid Data Architecture. The concept of Fluid Data that is embodied with the

architecture of the Compellent systems is that data can be automatically stored, moved, exported, or imported

based on the intelligence in the Compellent system. The advanced features of the Compellent system are

centered on managing and moving data to optimize the storage. In addition to block storage, the Compellent

system can have a NAS controller element added for file-based access.

As a midrange storage system, Compellent competes with EMC VNX and VNXe, HDS VSP G-Series, IBM Storwize

V7000, V5000, and V3700, NetApp FAS series, and the NetApp Engenio-based (E-Series) storage systems.

Highlights

Virtualization of the attached disk storage

Wide-striping of data blocks across all physical disks

RAID protection levels 0, 10, 5, 6

Data prioritization control of service level assignment to prioritize data access

Automated tiered storage

Add-on NAS controller the FS8600

Portable volumes to populate other Compellent storage systems

Snapshots with consistency groups

Additional element to provide file access using NAS protocols Live Volume storage hypervisor to present storage volume to two storage arrays for workload

migration and failover Active-active stretched cluster support

Perpetual license purchase of Storage Controller software once; continued on through multiple

generations of hardware

Two tiers of SSDs

SSD 3D NAND flash at 3.8TB supported

84 3.5 drives in 5U package

Encryption with Self-Encrypting Drives

Federation of multiple systems for management and volume migration

Evaluator Group Comment: The Dell Compellent Storage Center systems are targeted for a range of

customers from the higher end of the mid-tier market which is both price sensitive and has the

expectation for features originally resident in high-end systems to the most economical entry-level

market. There are many of the desired features in the Compellent system. The system is a very

popular choice by customers for its economics and the basic features. Additional features will help

expand the opportunity for Dell Compellent.


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Overview

The Dell Compellent Storage Center offers multiple models with usage as midrange storage and entry-level systems providing block storage. In addition to the block storage offered with the Compellent

system, another component may be added to the system to provide file-based storage as well. The

block storage system is a dual controller system where both controllers are active and support high

availability with failover from one controller to the other.

The dual controller system has implemented virtualization of the physical disks attached which has

enabled many advanced features including thin provisioning and wide striping. Highly valued advanced

features such as snapshots and remote replication are included with the system.

The add-on file-based capability is accomplished with the FS8600 Fluid File System which is a separate

appliance. The add-on NAS capability can scale from one appliance with two controllers to fourapplicance with eight controllers. Prior to the availability of the FS8600, NAS attachment for Compellent

was done with a server running the ZFS file system or the NX3000 NAS system (Windows Storage Server-

based) attached to the dual controller system. With this added element, both block and file-based

access can be supported.

Figure 1: Dell Compellent Storage Center Family (source: Dell)


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Figure 2: Dell Compellent Controller and SAS Drive Enclosures
http://www.compellent.com/Products/Hardware/Enclosures.aspx%23%23


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Product Architecture

The Dell Compellent Storage Center is a dual controller design with redundant components that allow

for failover in the case of failure of a controller and continued operation in the case of failure of other

components. The dual controller system uses communication through switches to detect failure in the

paired controller and handle the failover.

Physical disks are virtualized with blocks to be stored or retrieved managed across the disks in virtual

volumes. Using the indirection with the block locations not tied to specific disks prior to storing allows

for the features such as automated tiering, use of all physical resources, and redistribution of data to

avoid hotspots to be implemented. The virtualized architecture with blocks being handled

independently also gives flexibility in handling of the RAID protection and the ability to do wide striping

allowing for more simultaneous disk access.

Dell supports multiple types of SSDs as separate tiers of storage with migration between the tiers

handled by the standard Data Progression software.

Multiple RAID levels are supported with dynamic hot sparing. Any number of hot spares may be utilized

and the failover and rebuild are automatic.

The cache management allows for multiple threads to access cache with read-ahead algorithm for read

caching of data in system memory and a separate write cache mirrored across the controllers. The write

cache is battery backed to maintain data in the case of a failure or power loss.

I/O operations are monitored and optimized for performance by merging contiguous block requests into

a single request to minimize physical disk revolutions, sorting I/O request to minimize seek operations,

and deep tagged command queuing for multiple outstanding I/O requests to disks.

Another built-in unique feature is the ability to export and import volumes to a portable USB-attached

disk drive.

The controller has internal SSD disks used for operating system boot and for offloading battery-backed

cache in the case of a power failure. The operating system is a 64 bit OS beginning with SC 6.1.

The SC9000, SC8000, SC4000, and SCv2000 also support the Dell Fresh Air initiative and can operate at

elevated temperatures to reduce the need for air conditioning and associated power consumption. The

operating temperature can be up to 115 degrees F.

The file-based access is a NAS controller is the FS8600 Fluid File System (described in a separate

Evaluator Group document). The FS8600 is an appliance with two controllers. From one to four

appliances may be attached and provide a global namespace. Prior to the availability of the FS8600, NAS

was provided by either a server running a Linux operating system with the ZFS file system or the Dell

NX3000 NAS system. The NAS controller attaches to the Dell Compellent Storage Center for its block

storage while managing the file access using CIFS, NFS, and HTTP protocols. The block storage system

features such as thin provisioning and snapshots can be exploited with the NAS system.


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Evaluator Group Comments: Using dual controller architecture brings the high availability

characteristics expected in mid-tier systems to a broader market because of the economics of the

Compellent system. Probably the most important element of the architecture is that it abstracts the

physical disks and allows blocks to be moved and managed so that resources are optimized. This was

accomplished by a design that from the start targeted this abstraction and did not graft it on to an

existing design like some competing midrange storage systems.


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System Software

Disk Virtualization

All disks are arranged as a pool and logical volumes are created from the pool and presented to attachedservers for usage. The volumes created from the pool can be of any size and are thinly provisioned.

Copy-Mirror-Migrate

A local clone (copy) or mirror of a volume may be made using the same mechanism as the data

migration feature.

Disk Optimizer

When additional disks are added to the pool, data is restriped across the disks as a background activity

to spread the performance (disk access) across the disks in the pool

System Management

Enterprise Manager

The system management includes a web-based GUI for administration and resource management with

monitoring and reporting function built-in. The Enterprise Manager software contains monitoring and

reporting capabilities in addition to configuration and management. Enterprise Manager functions

include:

Monitoring and management of multiple local and remote Compellent systems

Configuration and control of remote replication

Monitoring and reporting on capacity and disk utilization Generate reports on storage utilization and performance

Manage alert notifications

Configure phone home support

Chargeback configuration (associating volumes to groups) and reporting

Dashboard display of status

CLI for manual interaction or scripting

Consolidated management with the FS8600 NAS

Enterprise Manager is a suite of individual elements with groupings into three levels. The Foundation

level is basic and is included with the product. The Reporter and Chargeback levels are optional and

additional charge.

Enterprise Manager Foundation Discovery, replication management, VMware SRM adapter, event

management, free space recovery

Enterprise Manager Reporter Performance management, capacity management, threshold alerting


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Enterprise Manager Chargeback Storage-based chargeback, power savings, and economic savings

(called Hero by Compellent)

Evaluator Group Comment: For a system targeted as a mid-range storage system, there aresystem management features that are typically on ly seen in high-end enterprise systems.


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Feature / FunctionSC9000 SC8000 SC4020

Form Factor Rack Mount

Number of Controllers2 with two 3.2 GHz 8-

core Xeon processors

2 with two 2.5 GHz 6-

core Xeon processors

1 or 2 with single 2.5 GHz

quad-core Xeon

processors

RAID Levels 0, 5, 6, 10

Maximum Disk DrivesSAS 960 - 12, 24 and

84 drives per enclosure

SAS 960 - 12, 24 and

84 drives per enclosure

120 (24 internal plus 96

external)

Drive Sizes Supported

SSD: 400 GB, 1.6 TB / 3.8 TB SAS

SAS 3.5: 450, 600 GB 15,000 RPM, 1, 2, 3, 4 TB 7,200 RPM

SAS 2.5: 146 GB 15,000 RPM, 450, 600, 900 GB 10,000 RPM

NL-SAS: 1 TB 7,200 RPM

Maximum Raw

Capacity3PB 3PB 500 TB

Device Interface Speed SAS: 12 Gb/s SAS: 6 Gb/s SAS: 6 Gb/s

Maximum backend

portsSAS 40 SAS 20 4

System Memory 256 GB per controller 32 128 GB 32 GB

NVRAM Capacity 512 MB 512 MB N/A

Drive intermix Yes Yes Yes

Drive spin-down No No No

Max iSCSI ports 20 @ 10 Gb/s 10 @ 10 Gb/s 4 @ 10 Gb/s

Max Fibre channel

ports

20 @ 16 Gb/s, 40 @

8Gb/s16 @ 16 Gb/s 8 @ 16 Gb/s

Max FCoE ports 12 @ 10 Gb/s 10 @ 10 Gb/s N/A

Table 1: Dell Compellent Model SC9000, SC8000 and SC4000 Comparison


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Feature / FunctionModel SCv2080 SCv2020 SCv2000

Form Factor Rack Mount

Number of Controllers2 with quad-core Xeon

processors

1 or 2 with quad-core Xeon

processors

1 or 2 with quad-core

Xeon processors

RAID Levels 0, 5, 6, 10

Maximum Disk Drives 168 168 168

Drive Sizes Supported

SSD: 400 GB, 1.6 TB SAS

SAS 3.5: 450, 600 GB 15,000 RPM, 1, 2, 3, 4 TB 7,200 RPM

SAS 2.5: 450, 600, 900 GB 10,000 RPM

NL-SAS: 1 TB 7,200 RPM

Maximum Raw Capacity 504 TB 504 TB 504 TB

Maximum backend ports 2 @ 6 Gb/s

System Memory 8 GB per controller 8 GB per controller 8 GB per controller

NVRAM Capacity 512 MB N/A

Drive intermix Yes Yes

Drive spin-down No No

iSCSI ports 2 @ 10 Gb/s, 4 @ 1Gb/s 2 @ 10 Gb/s, 4 @ 1Gb/s 2 @ 10 Gb/s, 4 @ 1Gb/s

Fibre channel ports 2 @ 16 Gb/s, 4 @ 8 Gb/s 2 @ 16 Gb/s, 4 @ 8 Gb/s 2 @ 16 Gb/s, 4 @ 8 Gb/s

SAS ports 4 @ 12 Gb/s 4 @ 12 Gb/s 4 @ 12 Gb/s

Table 2: Dell SCv2000 Models Comparison


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Host Operating System Support

Microsoft Windows Server, Hyper-V

Sun Solaris

HP-UX

Linux

IBM AIX

Novell Netware

Apple MacOS

Tru64

VMware ESX

Citrix XenServer

Microsoft Cluster Server Support

Table 3: Host OS Support

Multipath I/O failover is supported for the Windows MPIO driver. Microsofts Volume Shadow Copy

Service (VSS) is also supported for backup processes.

SMI-S is not specified as being supported.

Evaluator Group Comment: The specifications bring out the fact that the amount of cache in the

controllers is less than some competing products. Additional cache would allow for more cache hits

and write data for performance optimization.

The NAS controller for the Compellent Storage Center is the Dell FS8600 Fluid File System. This product

is described in the NAS section of the Evaluator Group Research. Prior to the availability of the FS8600,

there were two NAS controllers that were used to provide file access to Compellent.


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Reliability, Availability and Serviceability

The Compellent storage systems maintain data integrity and provide data availability via the

following mechanisms:

Dual controllers with failover for high availability

Redundant, how-swappable components:

- Controllers

- Fans

- Power supplies

Dual loop, switched connections to storage devices

Automatic drive failover

Automatic drive rebuild to spare drive

Configurable number of hot spare disks

RAID protection across storage devices

Remote reporting of status and automatic trigger of service actions

Mirrored, battery backed cache

Advanced Features

Dynamic Capacity (Thin Provisioning) Dynamic Capacity is Compellents name for thinprovisioning. With the architecture to abstract the physical disks and deal with blocks individually, as

capacity is required to store blocks of data, it is allocated dynamically and the space assigned to the

required volume. With the abstraction or virtualization of storage, all physical storage can be assigned

to a common pool to allow for better utilization. The allocation is done on a page basis where the page

size is 2 MB. For Windows environments only, there is a reclaim deleted or unused space back into the

common storage pool.

Automated Tiered Storage (Data Progression) Based on policy settings, the Compellent Storage

Center will automatically migrate data between tiers. The tiers that can be defined are for Solid State

Disk, high performance disk, or lower performance disk. In addition to the tiering function, additional

drives may be added to any tier and immediately utilized.

Data Instant Replay (Snapshot) Snapshots or Replays can be created at any time interval. The

Snapshots are copy on write with incremental changes captured to the read/write snapshot volume.With the management interface, a snapshot (or replay) can be restored to any point in time. There is no

logical limit on the number of snapshots that can be made.

Remote Instant Replay (Replication) Remote Instant Replay does an initial asynchronous

replication of a volume and then incremental changes are replicated asynchronously. Either Fibre

Channel or native IP interfaces may be used for the replication. One usage may be to use Portable

Volumes for the initial synchronization with changes only after the volume has been introduced at the

remote site. Synchronous replication of Live Volumes is supported over Fibre Channel networks.


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Dynamic Controllers (Clustering) Storage controllers may be run in clustering mode to provide for

high availability and additional performance. Multi-path software such as Microsoft MPIO is used to

failover access from servers. Cache is mirrored between the controllers.

Portable Volumes Portable Volumes are USB attached removable disks where a volume may be

copied and then introduced on another Compellent system. The Portable Volume can be used for

populated a remote system, seeding the replication volume in a remote replication solution, or for

creating a removable copy of a volume. Currently the Portable Volumes are 2 TB and have a 128-bit AES

encryption capability for the drive. The connection is USB 2.0.

Live Volume

Live Volume is a software-based function that introduces the concept of a storage hypervisor into the

Compellent system and provide Active-Active Stretched Cluster functionality. With Live Volume, storage

volumes can be presented to two Compellent storage systems at the same time. This allows

administrators to shift volumes between systems for application movement or high availabilityrequirements in case a system is being made unavailable for some reason. There is no limit to the

number of volumes or the number of transfers that may be done.

Live Volume is built upon Dell Compellent asynchronous replication where a volume it initially

synchronized to another Compellent system and then periodic snapshots are done with the changed

data replicated. Before a controlled swap is done, another snapshot is taken and the changed data

replicated. The switch of server access to a volume on the companion Compellent system involves

spoofing of the World Wide Name for the original access. The Live Volume can be switched back to the

original system with the same replication mechanisms. The configuration for the Live Volume is set up

through Enterprise Manager GUI and the swap can be initiated through the interface as well.

Live Volume works with vMotion and Microsoft Live Migration to allow the storage volume to move

when the virtual machines are moved. With the integration with the virtual machine software, when a

virtual machine is moved, the Live Volume can automatically be moved as well. Live Volumes have the

same capabilities of thin provisioning and tiering as other storage volumes.

VMware VAAI Support

The Dell Compellent system supports the VMware vStorage APIs for Array Integration (VAAI) which is in

vSphere 4.1. VAAI is a set of mechanisms that allow processing for certain data-related services

copying data when creating a new VM, for exampleto be offloaded from the ESX host to a storage

array. The intent of these APIs is to streamline the functioning of the ESX server and speed-up delivery ofstorage-supported services.

Full copy Enables the storage system to make full copies of data within the storage system

without having the ESX host read and write the data.

Block zeroing Enables storage systems to zero out a large number of blocks to speed

provisioning of virtual machines.


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Hardware-assisted locking The system uses an atomic test and set implementation rather

than a SCSI lock/reservation to protect the metadata for VMFS cluster file systems, thereby

improving the scalability of large ESX host farms sharing a Datastore.

Encryption

Encryption of data at rest is supported through the use of Self-Encrypting Drives. FIPS 140-2 certification

is included in the support. Storage Pools may be selected for encryption such that the entire system

does not require having all data encrypted.

Evaluator Group Comment: There are some very valuable features that can be exploited by

customers. The snapshot and asynchronous remote replication are very useful to operations.

An interesting feature is the Portable Volume. This feature has some unique usages and some

potential protection opportunities for customers. There are probably some unique cases that

customers have that will be very interesting to understand.

The Live Volume feature can be a very useful capability both for the movement of virtual machines

and to handle site failovers / switchovers. The granularity of one Compellent system to a second one

is a per-volume basis which means there could be multiple sites involving Compellent systems linked

together. Operationally, there can be advantages to being able to seamlessly direct the switchovers

as needed.

PerformanceNo SPC-1 performance information is available on the Storage Performance Council website at this time


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Evaluator Group Comments

The Dell Compellent Storage Center continues a very big success. It is offered through the reseller

channel and is a popular offering because of the price and the basic capabilities it provides for thetarget market of mid-size enterprises. The new controller will allow for greater performance and

scaling up market.

Positives:

Probably the most important thing to realize is that the Compellent system was designed from the

ground up as a system that virtualized the attached storage devices. This allowed for a design that

could build upon that without the constraints of other systems that evolved from fixed type device

mapping. The capabilities of thin provisioning and wide striping as well as the flexibility in handling

RAID protection were part of the initial design of virtualization.

The advanced features currently available are valued by customers most specifically the snapshot

and the asynchronous remote replication. Unique to the Compellent system is the Portable Volume

feature. This feature can be exploited in a number of ways and probably will lead competition to add

a similar capability at some point but after Compellent has already proved it to be a success.

The Live Volume feature has great operational value for customers in that it can be used to provide

access to volumes that are dynamically replicated between two Storage Center systems by servers in

case of failure or movement of the application to another server. The flexibility of providing access to

a volume through on Storage Center system or another that is transparent and can be seamlessly

switched is a feature that is usually only found on much more expensive systems. The simplicity ofswitching makes this capability more likely to be used by IT personnel.

Potential Concerns:

As the Compellent system is considered by customers who have had midrange systems with additional

advanced features, some of those features will be determining factors in purchases. Compellent will

need to continue to add more features such as a larger caching area and deduplication. These will be

competitive issues at some point in time to expand the market opportunity. The current product is still

very applicable for customers in the target market with excellent features and capabilities.

There is confusion sometimes with the Dell EqualLogic systems, which creates problems with

customers in making a selection. The potential acquisition by EMC also adds to some confusion.

More detailed information is available athttp://evaluatorgroup.com

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EGL2 Dell Compellent Storage Center-11