storage space sizing

8/13/2019 Storage Space Sizing

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Confidential - NetApp Employees Only

Space Sizing

The Final Frontier


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2008 NetApp. All rights reserved.

Agenda

The Space Problem how much to quote Terms and Concepts

Space Guarantees

Snap Reserve

Fractional Reserve

Vol

Autogrow

and Snap Autodelete

Possible configurations Recommendations



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The Problem

Customer asks for 20TB of usable storage for a SAN.

How much storage do you configure in your quote?



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The Problem

Why is this a problem?

Snapshots!!!!!!!!!!!!!!!

Why is this a problem?

Cost



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The Problem

So, youve had the snapshot conversation with the

customer.and you configure the 20TB usable quote

with how much storage?

2x plus delta? i.e. ((2x20)+(20%)) = 44TB usable

Why?



6/42 2008 NetApp. All rights reserved.

Terms and Concepts

Snapshots taken on a NetApp storage array are stored

in the same volume as the primary data

Snapshots taken on other vendors arrays are stored

in a separate snapshot area

On NetApp if you fill your volume with snapshot data

all writes to your LUNs stop and your host keels over

On other vendors arrays if you run out of snapshotspace the snapshot is failed




Terms and Concepts FlexVol Guarantees

Volume

Default guarantee for any new volume

Space is reserved from the aggregate at volume creation time

This space is not available to other volumes regardless of how much isreally used

Fractional Reserve settings can only be changed using Volume

guarantees

None

No space is reserved from the aggregate at volume creation time

Space is taken from the volume as data is written

Allows multiple volumes to use available space from an aggregate

Any individual volume still is not allowed to take more space than itsspecified size

Permits thin provisioning

at the volume level

File

The same as none but allows individual LUNs

(or files) to set space

reservations to ensure they have adequate spaceStick with guarantee=Volume unless you have good reason to do otherwise




Flexible Volume Space Management

Space Guarantees

Aggr

none

Aggr

volume file

NOTE: The blue blocks represent space not disks

Aggr

= claimed space

= unclaimed space

= full space




Space Guarantees Set to volume

Aggr

volume

NOTE: Blocks represent space not disks

= claimed space

= unclaimed space

= full space




Space Guarantees Set to none

none

= claimed space

= unclaimed space

= full space

NOTE: In reality, particular blocks are not claimed. The

volume is simply given a space limit, and space is filled

at random.




Space Guarantees Set to file

Aggr

file

= claimed space

= unclaimed space

= full space




Space Guarantees at FlexVol Creation

To specify a space guarantee at the creation of aFlexVol:

Example:

vol cr eat e sampl e_vol sampl e_aggr s f i l e si ze

10g

Step Action

1. Enter the following command:

vol cr eat e flexvol_name aggr_name s[ vol ume| f i l e| none] si ze [ k| m| g| t ]

2. Confirm settings, enter the following command:

vol opt i ons flexvol_name




Space Guarantees Change or Update

To change the space guarantee for an existingFlexVol volume:

Example:

vol opt i ons sampl e_vol guar ant ee none

Step Action

1. Enter the following command:

vol opt i ons flexvol_name aggr_name guar ant ee[ vol ume| f i l e| none]

2. Confirm settings, enter the following command:

vol opt i ons flexvol_name




Terms and Concepts - LUN Reservation

Determines when the space is taken out ofthe volume

At LUN creation (i.e. fully provisioned) When data is written to the LUN (i.e. thinprovisioned)

Equivalent of guarantees for LUNs

enable = volume

disable = none

Enabled by default

Only to be disabled for thin provision of LUNs

lun set reservation enable/disable

lun create o noreserve (creates a thin provisionedLUN)




Terms and Concepts - Snap Reserve

Set at the volume level

ONTAP removes the defined percentagefrom the volume

Does not allow LUNs to be created or files to growinto the snap reserve space

Snapshot data fills this space

Traditionally set to 0 for volumes used withblock protocols, but does not have to be zeroin SAN environments.




Snap Reserve

Volume 1 Space Reservation

20%

Snapshot Reserve

Volume 1 Space Reservation

20%

Snapshot Reserve

Snapshot Overflow

Figure 1 - DEFAULT Figure 2

Historically recommend setting Snap Reserve to

0 for block storage, but there are now reasons toreconsider this policy




Terms and Concepts - Fractional Reserve

Set at the volume level (default is 100%), can only bealtered if space guarantee = volume, can be setbetween 0% and 100%

Allows thin provisioning of snapshot space

Independent of Snap Reserve

Determines amount of space ONTAP reserves forsnapshot data for LUNs

Space is reserved when the first snapshot is taken.Space reserved = used space in LUN(s)

Fractional Reserve Space is only used if no otherspace in the volume is available




Fractional Reserve - Default

Example

Create the space reserved LUN

l un cr eat e s 100gb t ai x

/ vol / vol 1/ l un1Fractional Reserve = 100 %

guarantee = volume

space reservation

= enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full




Fractional Reserve - Default

Example (cont.)

Fill the LUN

guarantee = volume

space reservation

= enable

=

25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full


Fractional Reserve Default



Fractional Reserve - Default Example (cont.)

Take the Snapshot

snap cr eat e l un1 snap1

Space is Reservedguarantee = volume

space reservation

=

enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full


Fractional Reserve LUN Not Filled



Fractional Reserve - LUN Not Filled(cont.)

What happens if the LUN is not full whenthe snapshot is taken? Only the amount of space filled is reserved

guarantee = volume

space reservation

= enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full


Fractional Reserve 25 Percent



Fractional Reserve 25 Percent Example

Set Fractional Reservevol opt i ons vol 1 f r act i onal _r eser ve 25

Fractional Reserve = 25 %

guarantee = volume

space reservation

= enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full


Fractional Reserve 25 Percent


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Fractional Reserve 25 Percent Example (cont.)

Take Snapshot

Space is reserved

guarantee = volume

space reservation

= enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full


Fractional Reserve LUN Not Filled


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Fractional Reserve - LUN Not Filled(cont.)

What happens if fractional reserve is 25percent and the LUN is 50 percent full whenthe snapshot is taken? 12.5 GB are reserved

guarantee = volume

space reservation

= enable

= 25 GB

100 GB

= LUN1

= LUN1

= vol1

= reserved

=full



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Terms and Concepts - Snapshot Auto

Delete

Set on a per volume basis

Determines when (if) snapshots will be automatically deleted

Makes NetApp like competition but better

snap autodelete [on

| off

| show

| reset

| help] |

snap autodelete ...

Supported options and corresponding values:commitment

try, disrupt

trigger volume, snap_reserve, space_reserve

target_free_space

1-100

delete_order oldest_first, newest_first

defer_delete scheduled, user_created, prefix, none

prefix

Snapshots locked by clones, cifs or restores will not be deleted

change planned for 7.3Confidential - NetApp Employees Only


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Terms and Concepts - Volume Autosize

Set on a per volume basis

Determines if a volume should grow when nearly full

Possible settings

ON-

Maximum size (default 120% of initial size)

-

Increment size (default 5% of original size)

OFF

vol autosize [-m [k|m|g|t]][-i [k|m|g|t]][ on | off | reset ]

Try_first option determines whether auto_grow or auto_delete isattempted first

The possible try_first

values are:

snap_delete

volume_growe.g. vol options try_first snap_deleteConfidential - NetApp Employees Only

S M D f l


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Space Management Default

Configuration

Default Configuration:

Guarantee

= volume

LUN reservation = on

Fractional_reserve

= 100%

Snap_reserve= 0%

Auto_delete

= off

Auto_grow

= off

Try_first

= NA

Fractional

Reserve

TestLUN

Available

space

30GB

30GB

40GB


S M t D f lt


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Space Management Default

Configuration

Positives

Easy to manage/monitor space

Running out

of space only results in no additional

snapshots being created

SnapShots and active LUNs will always be available

Volumes are independent of each other

Negatives

Requires 2X + space

Puts us at a cost disadvantage versus competition



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Thin Provisioning Snapshot Space

Autodelete

Auto Delete Configuration:

Guarantee

= volume


Fractional_reserve

= 0%

Snap_reserve= 20%

Auto_delete

= snap_reserve

Auto_grow

= on

Try_first

= snap_delete

LUN

Available

space

20GB

20GB

60GB

Snapshot

Available

(Snap Reserve)

Preferred Configuration #1


Thi P i i i S h t S


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Autodelete

Positives

Easy to monitor/understand space

just volume (and .snapshot)

Sacrifices snapshots before active LUNs

Volumes are independent of each other

Looks like the competition

Negatives

Doesnt use shared space from the aggregate

(unless auto_grow

is also used)

Until ONTAP 7.3 have to be cautious with using

FlexClones



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Snapshot #1Snapshot #2

LUN #1 40GB

LUN #2 40GB

100% - 20 GB

Starting state

-

100GB Volume

- 2 x 40GB LUNs

-

snap_reserve = 20%

- fractional_reserve = 0%

Writing data to LUNs

Create snapshot #1Create snapshot #2

Volume is 100% full

Writes to LUNs are returned without of space

error messages

Application crashes!!

Filling Volume without autodelete



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Snapshot #1Snapshot #2

LUN #1 40GB

LUN #2 40GB

98% - 19.6GB

Writing data to LUNs

Create snapshot #1

Create snapshot #2

Snapshot #1 is autodeleted

Snapshot #2 is autodeleted

Snapshots are lost but applicationcontinues running

Filling Volume with autodelete

Starting state

-

100GB Volume

-

2 x 40GB LUNs

- snap_reserve = 20% - fractional_reserve = 0%

- trigger = snap_reserve

-

delete_order = oldest_first



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Vol Auto Size

Auto Grow Configuration:

Guarantee

= volume


Fractional_reserve

= 0%

Snap_reserve= 0% (or X%)

Auto_delete

= volume

Auto_grow

= on

Try_first

= auto_grow

LUN

Available

space

70GB

30GB

Preferred Configuration #2


Thi P i i i S h t S


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Auto Size

Positives

Uses shared free space from the aggregate for

possible growth

Sacrifices snapshots before active LUNs

Can tune amount of thin provisioning per volume

Works even with a smaller number of volumes Negatives

Volumes are not completely independent of oneanother

Always the case when using shared free space

Growth in one volume can limit growth of another


V l t i E l


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Volume autosize Example

vol aut osi ze vol 1 m 800gb i 150gb on

The current volume is 500GB

There are 2 LUNs

(160GB)

So with these 4 Snapshot copies, the volume is 98% full

Volume is 98%

full

LUN1 - 95GB

LUN2 95GB

Snapshot1 100GB

Snapshot 2 75GB

Snapshot 3 60GB

Snapshot 4 65GB


V l t i E l ( t )


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Volume autosize Example (cont.)


Now vol1 is 650GB, leaving 25 percent free space

LUN1 - 95GB

LUN2 95GB

Snapshot1 100GB

Snapshot 2 75GB

Snapshot 3 60GB

Snapshot 4 65GB


Volume t i Example (cont )


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Snapshot5, 145GB is added to the volume

LUN1 - 95GB

LUN2 95GB

Snapshot1 100GB

Snapshot 2 75GB

Snapshot 3 60GB

Snapshot 4 65GB

Snapshot 5 145GB


Volume t i Example (cont )


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Vol1 = 800GB

Max Growth

LUN1 - 95GB

LUN2 95GB

Snapshot1 100GB

Snapshot 2 75GB

Snapshot 3 60GB

Snapshot 4 65GB

Snapshot 5 145GB



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Configuration Options

Guarantee:

fractional

reservation:

snap

reserve: Trigger: Comment:

Volume 0% Y% volume

Probably doesn't make sense unless NAS data being written into the same

volume

Volume 0% (or X%) Y% (or 0%) snap_reserve

-Recommended config for auto delete

-

Easy to monitor free space

- Use fractional reserve >0% if using SME or SMSQL

Volume 0% Y% space_reserve -

Meaningless -

it will immediately delete every snapshot

Volume X% Y% volume

-

Probably doesn't make sense unless NAS data being written into the same

volume

Volume X% Y% snap_reserve

-

Easy to monitor amount of snapshot data

-

Provides some time if autodelete/autogrow

can't provide needed space

Volume X% Y% space_reserve -

Snapshot creation will be disabled when the volume is full

Volume 100% 0% N/A Default configuration for blocks

space overhead is very expensive

Volume 0% (or X%) 0% (or Y%) volume

-

Recommended config for auto_grow

-

Having fractional_reserve

set > 0% would provide some time if autodelete

or

autogrow

can't provide needed space, but can be confusing. Make fractional

reserve >0% if SME or SMSQL is used. Having SnapReserve

set to 20% would

also allow a trigger setting of snap_reserve

for snapshot deletes (if they were

enabled

but not for SQL or Exchange) and provide some snapshot buffer

space.

Volume X% 0% snap_reserve -

Meaningless -

it will immediately delete every snapshot

Volume X% 0% space_reserve -

Allows the use of the volume full warnings before snapshot deletion starts

File NA-100% 0% volume

-

Allows preference to newer snapshots by allowing new snapshots to be created

while deleting older

File NA-100% Y% snap_reserve-

Allows prefrence

to newer snapshots by allowing new snapshots to be created

while deleting older

File NA-100% Y% space_reserve - Meaningless - since fractional_reserve is 100%


Recommendations Method #1 AutoDelete


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Recommendations Method #1 AutoDelete

First

Make sure you include adequate PS resourcing

Target snapshot space at 20%-70%

Set fractional reserve to 0, volume guarantee = volume.

Set Snap Reserve at default 20%

Enable snap auto delete (trigger=snap_reserve ortrigger=space_reserve) and vol auto size

Set try_first

= snap_delete

Change default setting of wafl_reclaim_threshold

to 90 (default 98) if

trigger=snap_reserve, or lower if space_reserve

Put the remainder of your free space in your aggregate (this becomesglobal free space) and will equate to about 50% but may vary on avolume-by-volume basis

Vol

auto size is used as a last resort in case the snapshots I have

cannot

be deleted

Over time I may manually reallocate some of my global space into

selected volumes to increase LUN sizes or provide more snap reserve


Recommendations Method #2


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Recommendations Method #2

Auto_Grow First

Make sure you include adequate PS resourcing

Target snapshot space at 20%-70%

Set fractional reserve to 0, volume guarantee = volume..

Set Snap Reserve to 0

Enable snap auto delete (trigger=volume ortrigger=space_reserve) and vol

auto size

Set try_first

= volume_grow

Change default setting of wafl_reclaim_threshold

to 90 (default

98) remember the trigger for autogrow is always volume. Keep between 20% and 40% spare space in your volume (this isused for snapshot data but is not reserved for that purpose)

Put the remainder of your free space in your aggregate (thisbecomes global free space)

Snap delete is used only when the volume reaches max size orthere is no more space in aggregate.



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Recommendations - Exceptions

Size for performance first

Beware effects on performance if disk space

reduced DO NOT use snap auto delete

Instead use SME and SMSQL equivalents

storage space sizing

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