Sunday, January 01, 2006

Veritas Layered Volumes

Layered volumes are VxVM objects made on top of other VxVM volumes. They advantage is that they offer greater

Examples are

1. Stripe Pro OR (Raid 1 + 0) OR stripe-mirror
2. Concat Pro

The difference is that Concat Pro is concat LV over mirrored volumes and the former being stripe LV over mirrored

To convert from a non-layered to layered use the vxassist convert option.
Relayout works only between non-layered formats. For example we can relayout from stripe to concat.

Use the -o ordered option to gain some control over the disk assignment during layered volume creation.

The following command will create a layered volume as shown below

vxassist -g oradg -o ordered make oravol 150g layout=stripe-mirror ncol=2 mydisk01 mydisk02 mydisk03 mydisk04

mydisk01-01 mydisk02-01
mirror mirror
mydisk03-01 mydisk04-01

Heres a classic case from VxVM mailing list, I have modified it a bit to make things clear
and bring some brevity in the content presented.

Case : Converting Stripe volume to Stripe pro volume.

I need to set up a Stripe Pro (RAID 1+0) volume, I'm using 14 drives of a 22 drive Sun A5200 disk array (JBOD).
We have added a back plane with equal number of disks to the array. The front plane already has 6 disks in a stripe volume oravol.

I need to convert the oravol volume to a stripe pro for better redundancy.
FRONT:                   |     BACK:
-------------------            --------------------
c3t32  [oradb01] <-->  c3t48  [oradb02]
c3t33  [oradb03] <-->  c3t50  [oradb04]
c3t36  [oradb05] <-->  c3t52  [oradb06]
c3t37  [oradb07] <-->  c3t53  [oradb08]
c3t38  [oradb00] <-->  c3t54  [oradb10]
c3t40  [oradb11] <-->  c3t56  [oradb12]
c3t42  [oradb13]         c3t58  [oradb14] --------------à Spare
Any Ideas how to do this via actual command line recommendations?
Mirror all the disks on the other half, thus creating a mirrored stripe:
    # vxassist mirror oravol init=active \

Use vxassist to convert layout from RAID 0+1 to 1+0
    # vxassist  -g oradg  convert oravol layout=stripe-mirror,nolog


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