MSA2050 unable to add disk group

[Gwendling]

Hello,

I'm unable to create a new ssd diskgroup, i get the followinf error message :

"a performance tier cannot be added to a virtual pool that contains a read cache"

i have currently 4 diskgroups:

1 dga01 and rca1 in pool A , rca1 is just an SSD drive used in read cache

1 dgb01 and rcb1 in pool B, rcb1 is an SSD drive used in read cache

I installed a tiering licence on the system.

now i want to add a new disk group with 12 SSD drives and i get the error message.

How can i use this 12 new SDD drives in a new volume and leave the other's as they are ?

Thank's

Gérard

[SUBHAJIT KHANBARMAN_1]

You can't have Performance Tier and read cache in same Pool. You can have either Performance tier or read cache.

This is as per design.

So you can delete read cache for one Pool and create new VDG with SSD drives as Performance tier. 

This will be good because Performance tier will help you in both read/write performance enhancement but read cahe only help to improve read performance

Hope this helps!
Regards
Subhajit

I am an HPE employee

If you feel this was helpful please click the KUDOS! thumb below!

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[Gwendling]

Thank's Subhajit

Is it possible to juste delete the read cache SSD diskgroup without impact (other than performance) of the working system?

if yes , i will delete the read cache diskgroup in one pool, create a new disk group with 12 sdd and tiering will automaticly been enabled ?

This will be enabled on all volumes of the pool ? ( no way to do it on per volume basis ?)

thank's

Gérard

[SUBHAJIT KHANBARMAN_1]

Yes you can delete read cahe anytime.

No impact to production. Even if there is any data in read cache doesn't matter at all because actual data will be at the drive. Please note this is only help for read operation so no question of data loss.

Then create new VDG with all your SSD drives which will be Performance tier only.

There is some feature called Volume Tier Affinity where you can set at the volume level. This is an attribute that enables you to define QoS preferences for virtual volumes in a tiered environment. There are three Tier Affinity options:
• Archive—Prefers the lowest tier of service
• Performance—Prefers the higher tiers of service
• No Affinity—Uses the Standard Tiering strategy

You can check the below best practice whitepaper and refer section "Automated Tiering" and "Volume Tier Affinity" to get more details on this,

https://h20195.www2.hpe.com/v2/getpdf.aspx/A00015961ENW.pdf?

Hope this helps!
Regards
Subhajit

I am an HPE employee

If you feel this was helpful please click the KUDOS! thumb below!

**************************************************************************

[Gwendling]

I see , so there is no way to dedicate a new volume to the new SSD's

[Gwendling]

if create a new volume in the pool with a different type of disk group (SSD and SAS), this volume will automaticaticaly spread across the different disk groups ? no way to limit the volume on the SSD's ?

[SUBHAJIT KHANBARMAN_1 · Accepted solution]

No that's not possible because MSA 2050 fully virtualized array.

Earlier we had concept of linear array where dedicated vdisk concept was there which got created with dedicated drives. Later we used to create volume from these vdisks but in Virtual array we create volume from Pool. 

In Virtual Array concept only "Volume Tier Affinity" feature can help you with your requirement but keep in mind that this is not restricted or dedicated to particular tier. However to some extent this helps.

You can check the below SMU guide and refer page 93 and 99,

https://support.hpe.com/hpsc/doc/public/display?docId=a00017707en_us

"5. Optional: Specify a volume tier affinity setting to automatically associate the volume data with a specific tier, moving
all volume data to that tier whenever possible. The default is No Affinity. For more information on the volume tier
affinity feature, see “About automated tiered storage” (page 25)."

Hope this helps!
Regards
Subhajit

I am an HPE employee

If you feel this was helpful please click the KUDOS! thumb below!

**************************************************************************

[Gwendling]

I'm very happy with your quick and clear answers Subhajit.

many thank's

Gérard

[Gwendling]

One more question Subhajit if you read this :

is there a way to move disk groups between pool's ( without remove/recreate ...)

thank's

Gérard

[SUBHAJIT KHANBARMAN_1]

Virtual DIsk Group can't move from one Pool to another Pool.

There is one option called Volume Copy feature where it can copy volume from one Pool to another Pool. You can check this option.

Hope this helps!
Regards
Subhajit

I am an HPE employee

If you feel this was helpful please click the KUDOS! thumb below!

***************************************************************************

[Gwendling]

Thanks a lot  

Gérard