Backup mirror disks

[augusto cossa]

Good day,

I would like to know if somebody know how to do a full off line system backup on the machine which is mirrored and to let the users continue being connect. The idea is to stop a mirror and backup it and after that restart the sync. It's that possible? If it is would you sent me instruction on how to do.

Regards,
Augusto

[Robin Wakefield · Accepted solution]

From the lvsplit man page:

Split an online logical volume which is currently mounted on /usr so that a backup can take place:

lvsplit /dev/vg00/lvol1
fsck /dev/vg00/lvol1b
mount /dev/vg00/lvol1b /usr.backup

Perform a backup operation, then:

umount /usr.backup
lvmerge /dev/vg00/lvol1b /dev/vg00/lvol1

Robin.

[Thierry Poels_1]

Hi,
personally I really dislike splitting a single mirror. Mirroring is intended to guarantee your disks are 100% safe; if you split your mirror during backup which takes couple of hours, then your disks are only "safe" 80%-90% of the whole time. Imagine disk crash, reboot, backup procedure aborted, ... during backup.

Alternatives are :
-double mirroring: so you can split one mirror for backup and still have your disks mirrored. You "only" need 3 disks for every data disk ;)
-snapshot: if you have OnlineJFS you can create snapshots of your filesystems and backup that frozen situatin while users can keep on working.

regards,
Thierry.

[Paula J Frazer-Campbell]

Hi
Splitting a double mirror to do backups does place your data at risk whilst the backup is ongoing as you are running on a single disk.

I like many other sysadmins use a tripple mirror on my live data base and when I split the mirror to leave the bussiness running on a double mirrir.

I back up to disk (which is the quickest option) and as soon as this is complete I join the mirror back in and then start a backup routine which backs up the data from the static disk copy.

HTH

Paula

[Christian Schulze]

Hi

lvsplit or snapshot will probably work for static Files, but not for Database-Files (eg. Oracle) unless you you do an 'alter tablespace begin backup ...' before splitting to preserve Integrity of your Database.


correct me, if I'm wrong

Christian