Snapshots and Data Recovery

[sonny81]

Hoping to get some final clarification on this as there seems to be many different opinions on this matter.

I do complete backups of my entire Freenas to my Drobo frequently, but its possible to get minor data loss if I don't back a few files up before the Freenas crashes. To fix this I scheduled snapshots for each share every 15mins with a lifespan of 2 weeks.

1. With the above configuration, is my data reasonably safe?

2. If my RAIDZ2 fails should I rebuilt it per Freenas' instructions or is reformatting, copying over Drobo backups and copying over snapshots better?

3. In the event of a total RAIDZ2 failure, can I, like question 2, just copy over Drobo backups and restore snapshots for most recently modified files? What concerns me is that I'm reading snapshots can only be restored on the same volume they were created on. Its late here so its possible I'm just reading something wrong.

4. I know I can backup my snapshots through replication but can I configure that to save it to a LAN share connected to my router?

Greatly appreciate the clarity!!

 

[paleoN]

I do complete backups of my entire Freenas to my Drobo frequently, but its possible to get minor data loss if I don't back a few files up before the Freenas crashes. To fix this I scheduled snapshots for each share every 15mins with a lifespan of 2 weeks.

How will this help? The snapshots exist on your FreeNAS system.

1. Yes.
2. No idea what you mean here.
3. You would have to restore from backups as your pool failed.
4. Yes, you can save them to a file.
   Also, you can use rsync if you prefer.

 

[sonny81]

Question 3:
Basically I know my RAIDZ2 can survive two drive failures but if the entire RAID failed I would have 99% of my files on my Drobo backup. Since I only do Drobo backups weekly, I could loose a week's worth of files. I set up Snapshots to "fill in" for the time between manual backups.

So if I had to rebuild the RAIDZ2 with new drives, I could restore most of my files from my Drobo backup. The files I lost during that week would have been saved on Snapshots as I have them set up to occur every 15mins.

With that, a better way of asking is: Can I rebuild a failed RAIDZ2, copy the files over from the Drobo backup, and restore the "extra" files/more recent files with Snapshots? The language "snapshots can only be restored on the same volume they were created on" doesn't make sense if I'm reading it right. Seems that snap shots can do anything for me if I have to remake a pool.

Thoughts?

 

[sonny81]

I hate the expense of it, but rsync is looking pretty good. Would I be able to set it up to back up to my Drobo FS via ethernet? Wasn't sure if the receiving host needed to be ZFS as well.

 

[paleoN]

With that, a better way of asking is: Can I rebuild a failed RAIDZ2, copy the files over from the Drobo backup, and restore the "extra" files/more recent files with Snapshots? The language "snapshots can only be restored on the same volume they were created on" doesn't make sense if I'm reading it right. Seems that snap shots can do anything for me if I have to remake a pool.

You are missing a step or misunderstanding. If you have a full backup on the Drobo last Sunday and snapshots on the raidz2 pool, if the entire pool fails you only have the backup from last Sunday as the snapshots are in the pool. You have to save the snapshots to someplace else, e.g. Drobo. You can't restore an incremental snapshot without having a full snapshot for the filesystem in question.

I hate the expense of it, but rsync is looking pretty good. Would I be able to set it up to back up to my Drobo FS via ethernet? Wasn't sure if the receiving host needed to be ZFS as well.

It appears to me that rsync is simpler to setup, but I haven't played with snapshots all that much. You can rsync or zfs send piped to a file to whatever filesystem. I doubt you are using any ZFS specific filesystem attributes that you need to keep. While the Drobo doesn't offer end-to-end checksumming any backup is better than no backup.