Mirrored disks

[Otto Folprecht]

I need to map out our mirrored disks. All of our disks are mirrored but I need to understand the pairing structure. My goal is to mark the disks that are mapped one to another in order to have a better understanding of our system performance. How do I map the disks?

THX

Otto

[Mel Burslan]

If you are using LVM, the easiest way of checking this out is to verify that your logical volumes were created with the strict allocation, as follows

lvdisplay /dev/vgXX/lvolXX|grep ^Allocation

if it is no strict, this does not necessarily mean that volumes are mirrored on the same disk but it opens the possibility of doing such thing. If allocation is not strict you need to look at the output of

lvdisplay -v /dev/vgXX/lvolXX

and compare the fields $2 and $6 on lines which look like the list below

00000 /dev/dsk/c2t0d0 00407 current /dev/dsk/c2t1d0 00407 current
00001 /dev/dsk/c2t0d0 00408 current /dev/dsk/c2t1d0 00408 current
00002 /dev/dsk/c2t0d0 00409 current /dev/dsk/c2t1d0 00409 current
00003 /dev/dsk/c2t0d0 00410 current /dev/dsk/c2t1d0 00410 current


Hope this helps

[Otto Folprecht]

Mel, The allocation is strict. What would be the next step?

[Mel Burslan]

Then there should not be anything to worry about for you. Your actual data and the mirrors are on separate physical disks/LUNs (as much physically separate a LUN can get that is).

If you want to see the location of the data and mirror, you need to run lvdisplay -v against all logical volumes and look for the sections I have given a sample of in my first post.

[Wayne Patton_1]

The above answers are correct. LVm does not really mirror a disk to another disk. It mirrors the LVm extents. It makes sure that to two mirrored extents are on different disks. But all the extents on one disk may or may not be on just 1 other disk, expecially if the disks are different sizes.

wayne