Celerra Manual Volume management with 24 drives in stripe volume

If you want to have various filesystems sharing the same volume/pool, and have all of the filesystems striped across all disks, then you will want to use slices as well.

Disk/LUN -> Slice -> Stripe -> Meta

(or)

Disk/LUN -> Stripe -> Slice -> Meta

Using the slice allows you to create multiple smaller Metavolumes and expand/shrink them.  If you only want one MetaVolume with multiple filesystems, then you can probably leave out the slice layer and just stripe across the LUNs and create a single Meta on the stripe.  If you want slices, the first option would be slightly easier to manage.  You create a single Meta across all of the disks after they've been sliced and striped, then create filesystems as needed from that same Meta.

As far as RAID groups, generally the more raid groups you use, the more LUNs you will have, and the more queues you will get.  Ideal LUN count is increments of 4, with 8 being a good quantity to use in a single pool or meta.  The normal RAID 10 config for Celerra is 1+1 so with 24 drives you will get 12 RAID groups and probably 24 LUNs.

DO NOT Stripe across multiple LUNs in the same RAID Group.. If you want to use 2 LUNs per group, create 2 stripes, one across LUN1 in each group, another across the LUN2 in each group, then create the meta with both stripes.  The Meta will concatenate the two stripes.

Make sure to specify the 32KB stripe size when you create the stripe volume, though I believe it is the default still.

Hope that helps.

Hi Richard,

Thanks for explaining this well. I have a question on the above suggestion.

" If you want to use 2 LUNs per group, create 2 stripes, one across LUN1 in each group, another across the LUN2 in each group, then create the meta with both stripes.  The Meta will concatenate the two stripes."

In this case if I am striping all SPA owned luns (first lun from R10)  together and all SPB owned luns (2nd Lun) together and create a meta out of this two stripes, then is there a chance that all the backend lun will fall to one single SP for the ownership?.

Thanks

Mohandas

Sorry for the delayed response, I didn't see this reply...

Stripes, Slices, and Metas created in the Celerra don't affect SP ownership, since the Celerra is essentially a host and has access to both SPs.  For best load balancing you'd want to stripe something like the following..

With the following example LUNs created:

RG1 - LUN1 - SPA

RG1 - LUN2 - SPB

RG2 - LUN3 - SPB

RG2 - LUN4 - SPA

RG3 - LUN5 - SPA

RG3 - LUN6 - SPB

RG4 - LUN7 - SPB

RG4 - LUN8 - SPB

Stripe 1 = LUNs 1,3,5,7

Stripe 2 = LUNs 2,4,6,8

Meta 1 = Stripes 1 and 2

Since a Meta is a concatenation of the two stripes, if all LUNs in Stripe 1 were owned by SPA, and all LUNs in Stripe 2 were on SPB, then ALL IO would fall on SPA until you filled the capacity of the Meta to 50%, after which SPB would begin to see IO and slowly grow.  By alternating SPs in a single stripe, you ensure even loading of the SPs from 0 capacity to full.

I have a question about this.  I have the following scenario.  I need to create one meta volume that contains 10 Raid 1 Luns that have been carved out of 5 Raid1 raid Groups.  this is the way the luns are laid out:

RG1: Lun 1(SPA) - Lun 2 (SPB)

RG2 :Lun 3(SPA) - Lun 4 (SPB)

RG3 :Lun 5(SPA) - Lun 6 (SPB)

RG4 :Lun 7(SPA) - Lun 8 (SPB)

RG5 :Lun 9(SPA) - Lun 10 (SPB)

With this layout how shoudl I create my two stripes?