Snapshots fail on large FFS2 volumes regulary -- how to backup /usr/home?!

[Kirk McKusick]

> Date: Thu, 19 May 2011 21:17:55 +0400
> From: Lev Serebryakov <lev at freebsd.org>
> To: freebsd-fs at freebsd.org
> 
> Hello, Freebsd-fs.
> 
>   I have /usr/home partition on my new server which is 400GiB (only
> 17GiB is used). It is UFS2, SoftUpdates are enabled.
> 
>   I want to backup it on live system, but 4 times out of 5 I got
> (after 10-12 minutes of wait! Oh my, 10 minutes to create snapshot!):
> 
> mksnap_ffs: Cannot create snapshot /usr/home/.snap/dump_snapshot: Resource temporarily unavailable
> dump: Cannot create /usr/home/.snap/dump_snapshot: No such file or directory
> 
>   It is FreeBSD 8.2-STABLE/amd64, 8GiB of memory.
> 
>   I've never encounter such problem on previous server, which has
>  about 80GiB (with 20GiB used).
> 
> -- 
> // Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>
> 
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Given the size of your storage, you should consider using ZFS
which is better able to handle such large systems better.

My second suggestion is that you try building UFS2 with 32K
blocks and 4K fragments. That will reduce the number of resources
needed to take the snapshot.

	Kirk McKusick