snmetadump?

morphenine · Xsan Master Joined: 22 Dec 2008 Posts: 126

Okay, I'm a little confused after reading the man page on this command.

I understand that this command will dump your metadata to a file that can be backed up (which will be usable for a restore for about a nanosecond after the volume is restarted).

What exactly is it referring to when it differentiates between a managed and unmanaged filesystem? Has anyone used this command? What did you use it for? How well did it work?

I'm curious about this command since there is little other talk of it besides the man page.

MattG · Xsan Master Joined: 15 Apr 2005 Posts: 456

We use it as a crutch whenever we are repairing or transforming the MD LUN of an Xsan volume. For instance, when rebuilding the LUN with newer drives, we will run snmetadump to have a copy of the MD at the ready, just in case we need to start from scratch. So far, we've never needed to use it.

abstractrude · Xsan Master Joined: 13 Mar 2008 Posts: 860

mattg
have you ever tried scripting this command? like doing a nightly metadeta dump? i did in a tets environment and it worked like a charm, but test is one thing...

morphenine · Xsan Master Joined: 22 Dec 2008 Posts: 126

What would be the purpose/benefit of a nightly metadata dump? Isnt the metadata unusable as soon as you make any change to the volume?

MattG · Xsan Master Joined: 15 Apr 2005 Posts: 456

It is perfectly useless as soon as changes start happening to the volume, but imperfectly useful at any time, as long as you understand that new files that were created and old files that were deleted will not be accessible. That, as they say, is better than nothing.

We've never put an snmetadump into a backup regimen for any client. The files on the volume itself need to be backed up. We use snmetadump as a backup whenever doing any kind of surgery to the metadata LUN itself, such as upgrading the drives in a RAID1.

abstractrude · Xsan Master Joined: 13 Mar 2008 Posts: 860

was more of a just curious kind of thing. I also was thinking about how snapshotting metadata and including it in tape backup routines could be helpful. This is more of a academic exercise than anything.

Now this is my understanding, you could restore the backed up metadata, say if you lost your metadata lun. then cvfsck to sync it up to your filesystem. So data that is not avalible in the journal would be cleaned be avaliible. Im thinking I might do this in a test environment just for kicks.

seems like it would be a smart idea to do this before bandwith expansions and the such. what do you think matt.[/i]