Saturday, 12 January 2008

Updating the backup process

When I upgraded from OpenSUSE 10.1 to 10.3, I took the decision to migrate away from XFS and use EXT3. Although XFS had served me well for many years, I felt the simplicity of using the "standard" Linux filesystem would make restores easier. For large filesystems with high throughput, XFS is fantastic, but for more home workstation, I don't think there is much in it. Actually, if anything, EXT3 is more responsive when doing a backup.

In making the change, I had to modify my backup scripts to use ext3 dump instead of xfsdump. This gave me the chance to revisit the LVM snapshot section I wrote a few years ago, but could not get working with the kernel supplied with 10.1 (It worked. Sometimes).

The new script is very simple and does the following:

1) Takes a filesystem to dump and dump level to take (0 = full, 1=everything that has changed since the last level 0, 2=everything that has changed since the last level 1 etc.).
2) Works out the underlying LVM logical volume the filesystem is built on.
3) Creates a snapshot of the logical volume and mounts in under /snapshot
4) Performs a dump of /snapshot to my external (Firewire) hard disk.
5) Umounts /snapshot and destroys the snapshot.

It appears to be working pretty well and provides what should be a very simple mechanism for ensuring my main workstation is backed up.

T's Vista PC is backed up to another external Firewire hard disk using the built in Vista tools. This appears to do the job and happens automatically, so it's a fire-and-forget operation.

I'm not currently backing up the Mac. This shouldn't be a problem because all my important files are stored on the network. It also seems that Time Machine has some limitations (setting backup schedules, limited to using local storage etc.). I'm guessing a future version of Mac OS X will fully support ZFS and will use ZFS snapshots for backing up.

This leaves the "SilverShuttle" which is my VMware Server / Solaris server. This needs some form of backup and I'm still chewing over the options. I'd ideally like a large external array with a bunch of disks that are managed by ZFS, but this doesn't solve my desire to keep an off-site copy of my data. Something for me to work on then...

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