Backing up an LSM volume

From: Monroe, David <David_at_psds.com>
Date: Fri, 28 May 1999 12:07:59 -0700

Hello Managers!

I checked the archives and didn't see anything relating to this. We
have an AlphaServer 4100 with two KZPAC RAID controllers (to reduce the
single point of failure) with a mirrored RAID 5 set (3 drives connected
to each RAID controller, each 3-drive RAID set is configured as a
hardware RAID 5, and LSM is used to mirror the two RAID 5 sets between
the two controllers). We're using the UFS file system.

I'm trying to back up each file system using the "dump" command, then
verify the integrity of the backup. I figured it would be quickest to
create a partition outside LSM on a new drive to hold the test backup
(i.e. rz8g). This way I could mount the separate partition after the
dump and view the files (I know this works when dumping non-LSM
partitions--we can typically duplicate file systems on a drive this
way). However, after the dump from the LSM volume to the rz8g disk
partition, I can no longer mount /dev/rz8g. It tells me that "No valid
filesystem exists on this partition". Before the dump, I could mount
it. I expected to see a mirror image of the volume that I just backed
up.

Here's the process I used. We are temporarily breaking the mirror to
make the backup since we don't have enough space on the volume to do a
snapshot.

*** Dismount the mirror set, so we can just back up the mirror volume.
volplex dis vol-re0g-02
      
*** Make a new temporary volume for the mirror set
volmake -Ufsgen vol vtmp plex=vol-re0g-02
volume start vtmp

*** Check it, just to be safe
fsck -p /dev/rvol/vtmp

*** Back up the volume
dump -0 -f /dev/rz8g /dev/rvol/vtmp

*** Re-attach the mirror volume. . .

When I try to mount /dev/rz8g after the dump step, it gives the "No
valid filesystem..." error. How do I know that my backup was
successful?
Is there a simple way to verify the integrity of the backup?
What if we need to restore the data to a non-LSM partition in the
future?

Any input on this would be most appreciated.

David

-----------------------
David Monroe
Puget Sound Data Systems, Inc.
mailto:david_at_psds.com

      
Received on Fri May 28 1999 - 19:06:30 NZST

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