Veritas Layered Volumes

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

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
volumes.

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

    stripe
 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?

Solution

Mirror all the disks on the other half, thus creating a mirrored stripe:

    --------------------------------------------------------------------------------------

    # vxassist mirror oravol init=active \

    alloc=oradb02,oradb04,oradb06,oradb08,oradb10,oradb12

    Use vxassist to convert layout from RAID 0+1 to 1+0

    -----------------------------------------------------------------

    # vxassist  -g oradg  convert oravol layout=stripe-mirror,nolog