M06 PhysicalStorage FINAL

7/29/2019 M06 PhysicalStorage FINAL

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Physical StorageManagement

Module 6

Data ONTAP 7.3 Fundamentals


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2008 NetApp. All rights reserved. 2

Module Objectives

By the end of this module, you should be able to:

Describe Data ONTAP RAID technology

Identify a disk in a disk shelf based on its ID

Execute commands to determine disk ID

Identify a hot-spare disk in an FAS system

Calculate usable disk space

Describe the effects of using multiple disk

types

Execute aggregate commands in Data ONTAP

Define and create an aggregate


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Disks


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Disks

All data is stored on disks

To understand how physical media is

managed in your storage system, we will

address:

Disk types Disk qualification

Disk ownership

Spare disks


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Supported Disk Topologies

FC-AL

FAS2000 FAS3000 FAS6000

SATA

FAS2000 FAS3000 FAS6000 R200


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Disk Qualification

Use only NetApp Qualified Disks Modifying the DiskQualification Requirement

file can cause your

storage system to halt.


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Disk Ownership

Disks must be assigned to (owned by) a

controller.

Software Disk Ownership Hardware Disk Ownership

Ownership is assigned

FAS270

FAS3000 series

FAS2000 series

FAS6000 series

Ownership is based on slot used

R200

FAS250

FAS3000 series



system> sysconfig -r

Volume vol0 (online, normal) (block checksums)Plex /vol0/plex0 (online, normal, active)

RAID group /vol0/plex0/rg0 (normal)

RAID Disk Device HA SHELF BAY CHAN Used (M...

parity 3a.16 4a 1 0 FC:A 17000/...

data 3b.17 4a 1 1 FC:A 17000/...

Disk Ownership

Disk ID = Loop_id.Device_id



Disk Ownership: Loop_id

The loop_id is the designation

for the slot and port where anadapter is located. In the

following illustration, the loop_id

is 3b.

PROPERLYSHUTD OWNSYSTEMBEFOREOPENINGCHASSIS.

PCI 1 PCI 3

PCI 4PCI 2

DISCONNECTAC POWER

CORDBEFOREREMOVAL

I

O

AC

status

DISCONNECTAC POWER

CORDBEFOREREMOVAL

I

O

AC

status

Console

Console

0a 0b

0a 0b

F C

F C

e0a

e0a e0b

e0b RLM

RLM

e0c

e0c e0d

e0d

0d

0d0c

0c

F C

F C

0e

0e

LVDSCSI

LVDSCSI

L

I

N

K

L

I

N

K

L

I

N

K

L

I

N

K

L

I

N

K

L

I

N

K

L

I

N

K

L

I

N

K

3b



Disk Ownership: Device_id

Shelf ID Bay Number Device ID

1 130 2916

2 130 4532

3 130 61484 130 7764

5 130 9380

6 130 10996

7 130 125112

Shelf ID

12345678910111213 Bay Number0



The fcstat device_map Command

Use the fcstat command to troubleshoot

disks and shelves.

Use the fcstat device_map command to

show disks and their relative physical position

map of drives on an FC loop.



Matching Disk Speeds

When creating an aggregate or traditional

volume, Data ONTAP selects disks:

With same speed

That match speed of existing disks

Data ONTAP verifies that adequate spares areavailable



Using Multiple Disk Types in an Aggregate

Drives in an aggregate can be:

Different speeds

On the same shelf or on different

shelves

Avoid mixing drive types within an

aggregate

The spares pool is global1 2

3 4 5 6



system> disk zero spares

Spare Disks

What is the purpose of spare disks?

Increase aggregate capacity

Replace failed disks

Zeros disk automatically when the disk is

brought into use It is best to zero drives in the spares pool in

advance, allowing Data ONTAP to use the

drives immediately



Sizing



Disk Sizing

To properly provision NetApp storage systems,

you must know how disk sizes are calculated:

All disks are right-sized

Count the size of data disks, not parity disks

NOTE: The df command does not reflect parity disks.

Use df -h to view the output in a format you

can read



Right-Sizing

Disk Type Disk Size Right-Sized Capacity Available Blocks

FC/SCSI 72 GB 68 GB 139,264,000

144 GB 136 GB 278,528,000

300 GB 272 GB 557,056,000

ATA/SATA 160 GB 136 GB 278,258,000

250 GB 212 GB 434,176,000

320 GB 274 GB 561,971,200

500 GB 423 GB 866,531,584

NOTE: ATA drives have only 512 bytes per sector and lose an

additional 1/9 or 12.5% due to block checksum allocation.



Usable Disk Space

When disks are right-sized, 10% of the space

is reserved for WAFL. This reserved space is:

Used for system and core usage to maximize

disk efficiency

Similar to other operating systems (for example,the UNIX FFS)

The space that remains after right-sizing is

usable disk space, which can be used for

either:

Traditional volumes

Aggregates with flexible volumes



Disk Space Allocation: Aggregates

Aggregates with a

Traditional VolumeEachaggregate has 10%allocated for WAFL.

Traditional VolumesEachvolume has 20% allocatedfor Snapshot reserve. The

remainder is used for clientdata.

Snapshot ReserveTheamount of space allocatedfor Snapshot reserve is

adjustable. To use thisspace for data (notrecommended), you mustmanually override theallocation used forSnapshot copies.

WAFL Overhead

WAFL Aggregate

Space

10%

90%

Aggregate

Space

80%

20%(Adjustable)

Snapshot Reserve



Disk Space Allocation: Flexible Volumes

AggregatesEach

aggregate has 5%allocated for Snapshotreserve and 10% allocatedfor WAFL.

Flexible VolumesEachvolume has 20% allocated

for Snapshot reserve. Theremainder is used for clientdata.

Snapshot ReserveTheamount of space allocated

for Snapshot reserve isadjustable. To use thisspace for data (notrecommended), you mustmanually override theallocation used for

Snapshot copies.

FlexVol

Space

Plus

Aggregate

Snapshot

Reserve

WAFL Overhead

WAFL Aggregate

Space

10%

90%

Aggregate

Space

95%

5%(Adjustable)

Aggregate Snapshot Reserve

FlexVol1x

FlexVol#n

.snapshot 20%

80%

20%

80%

.snapshot



Disk Protection


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Disk Protection

Data ONTAP protects disks through:

RAID

Disk scrubbing

Data ONTAP can assist in recovering from disk

failures


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RAID Groups

RAID groups are a collection of data disks and

parity disks

RAID groups provide protection through parity

Data ONTAP organizes disks into RAID groups

Data ONTAP supports:

RAID 4

RAID-DP


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RAID 4 Technology

RAID 4 protects against data loss that results from a

single-disk failure in a RAID group

A RAID 4 group requires a minimum of two disks:

One parity disk

One data disk

Parity Data Data Data Data Data Data Data


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RAID-DP Technology

RAID-DP protects against data loss that results from

double-disk failures in a RAID group A RAID-DP group requires a minimum of three disks:

One parity disk

One double-parity disk

One data disk

Parity Double-

Parity

Data Data Data Data Data Data


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RAID Group Size

RAID-DP

NetApp

Platform MinimumGroup Size MaximumGroup Size DefaultGroup SizeAll storage systems (with

SATA disks) 3 16 14All storage systems (with

FC disks) 3 28 16

RAID 4

NetApp

Platform MinimumGroup Size MaximumGroup Size DefaultGroup SizeFAS270 2 14 7

All other storage systems

(with SATA) 2 7 7All other storage systems

(with FC) 2 14 8


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Data Reliability

RAID-level checksums enhance data

protection and reliability

Two processes:

options raid.media_scrub

Checks for media errors only If enabled, runs continuously in the background

options raid.scrub(also called disk

scrubbing)

Checks for media errors

Corrects parity consistency


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RAID Checksums

Zone Checksums (ZCS)

Eight 512-byte sectors (4,096 bytes) per block

Every 64th block checksums the previous 63

WAFL never uses these checksum blocks; RAID does

Available for V-Series

Block Checksums (BCS)

Eight 512-byte sectors (4096 bytes) per block

Every sector checksums itself

Are faster than ZCS

Are the standard for FC, SCSI and V-Series disks

8/9ths ATA disks; every ninth sector checksums the

previous eight


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Comparing Media and RAID Scrubs

A media scrub:

Is always running in thebackground when the storagesystem is not busy

Looks for unreadable blocksat the lowest level (0s and 1s)

Is unaware of the data stored

in a block Takes corrective action when

it finds too many unreadableblocks on a disk (sendswarnings or fails a disk,depending on findings)

A RAID scrub:

Is enabled by default Can be scheduled or disabled

Disabling is notrecommended

Uses RAID checksums

Reads a block and then

checks the data If the RAID scrub finds a

discrepancy between theRAID checksum and the dataread, it re-creates the datafrom parity and writes it back

to the block Ensures that data has not

become stale by readingevery block in an aggregate,even when users haventaccessed the data


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About Disk Scrubbing

Automatic RAID scrub:

By default, begins at 1 a.m. on Sundays

Schedule can be changed by an administrator

Duration can be specified by an administrator

Manual RAID scrub overrides automaticsettings

To scrub disks manually:

raid.scrub.enable off

And then:aggr scrub start

To view scrub status:

aggr scrub status aggr_name


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RAID Group Options

NOTE: For a complete list of RAID options, see your product

documentation.

options raid.timeout

options raid.reconstruct.perf_impact

options raid.scrub.enable

options raid.scrub.perf_impact

vol options raidtype

aggr options raidtype


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disk Commands

disk fail diskname

disk remove diskname

disk swap

disk unswap

disk replace [start|stop]

disk zero spares

disk scrub [start|stop]

disk sanitize


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Disk Failures

Spares are global.

Raid Group 0 Spares

Volume 1

DataData DataParity


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Degraded Mode

Degraded mode occurs when:

A single disk fails in a RAID 4 group with no spares Two disks fail in a RAID-DP group with no spares

Degraded modes operates for 24 hours, during whichtime:

Data is still available

Performance is less-than-optimal Data must be recalculated from the parity until the failed disk

is replaced

CPU usage increases to calculate from parity

System shuts down after 24 hours

To change time interval, use the optionsraid.timeout command

If an additional disk in the RAID group fails duringdegraded mode, the result will be data loss


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Replacing a Failed Disk by Hot Swapping

Hot-swapping is the process of removing or

installing a disk drive while system is running

and allows for:

Minimal interruption

The addition of new disks as needed Removing two disks from a RAID 4 group:

Double-disk failure

Data loss will occur

Removing two disks from a RAID-DP group:

Degraded mode

No data loss


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Replacing Failed Disks

NOTE: Disk resizing occurs if a smaller disk is replaced by a

larger one.

1 TB 750 GB 750 GB 750 GB 750 GB

750 GB


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Aggregates


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Aggregates

Aggregates representphysicalstorage:

Made up of one or more RAID groups

A RAID group includes:

One or more data disks

Parity disks

RAID 4 has only one parity disk

RAID-DP has two parity disks

Data is striped for parity protection

A flexible volume depends on an aggregate for

physical storage


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Naming Rules for Aggregates

An aggregate name must:

Begin with either a letter or the underscore

character (_)

Contain only letters, digits, and underscore

characters (_) Contain no more than 255 characters


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Adding an Aggregate

To add an aggregate using the CLI:

aggr create

To add an aggregate using FilerView, use theAggregate Wizard

When adding aggregates, you must have thefollowing information available:

Aggregate name

Parity (DP is default)

RAID group size (minimum) Disk selection method

Disk size

Number of disks (including parity)


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Creating an Aggregate Using the CLI

The following is an example of a CLI entry used

to create an aggregate:

system> aggr create aggr_name 24

Creates an aggregate called aggr_name with24 disks

By default, this aggregate uses RAID-DP

Using the default, 4 of the 24 disks are paritydrives


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Common Aggregate Commands

aggr create [options]

aggr add [options]

aggr status [options]

aggr rename

aggr show_space [-b] aggr offline { | }

aggr online { | }

aggr destroy { | }

Creating an Aggregate Using


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Creating an Aggregate Using

the FilerView Aggregate Wizard


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Aggregate Size

In Data ONTAPprior to version 7.3:

Aggregate size is calculated using:

sysconfig r

All disks in the aggregate (parity and data) are

includedIn Data ONTAP 7.3:

Aggregate size is calculated using the size of

data disks Only data disks in the aggregate are included

(parity disks are excluded)


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Module Summary

In this module, you should have learned to:

NetApp supports FC-AL and SATA disk drives

Use either FilerView or the CLI to find disk

information

Data ONTAP organizes disks into RAID groups

RAID groups consist of data disks and parity

disks

Degraded mode occurs when a single diskfails in a RAID 4 group with no spares, or two

disks fail in a RAID-DP group with no spares


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Exercise

Module 6: Physical Storage

ManagementEstimated Time: 60 minutes


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Answers

Module 6: Physical Storage

Management


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Check Your Understanding

What is a RAID group?

A collection of disks organized to protect data

that includes:

One or more data disks

Data striped for performance One or two parity disks for protection

Why use double parity?

To protect against a double-disk failure


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Check Your Understanding (Cont.)

How many RAID groups does the following

command create?aggr create newaggr 32

Assuming a default RAID group size of 16, this

creates two RAID groups What is the minimum size of a RAID-DP

group?

Three disks (one data, two parity)

Documents

M06 PhysicalStorage FINAL