running mksnap_ffs

[LI Xin]

Willem Jan Withagen wrote:
> Hi,
> 
> I got the following Filesystem:
> Filesystem    Size    Used   Avail Capacity iused     ifree %iused
> /dev/da0a     1.3T    422G    823G    34%  565952 182833470    0%
> 
> Running of a 3ware 9550, on a dual core Opteron 242 with 1Gb.
> The system is used as SMB/NFS server for my other systems here.
> 
> I would like to make weekly snapshots, but manually running mksnap_ffs
> freezes access to the disk (I sort of expected that) but the process
> never terminates. So I let is sit overnight, but looking a gstat did not
> reveil any activity what so ever...
> The disk was not released, mksnap_ffs could not be terminated.
> And things resulted in me rebooting the system.
> 
> So:
>  - How long should I expect making a snapshot to take:
>     5, 15, 30min, 1, 2 hour or even more???

This depends how much cylinder groups do you have.  If you have a lot of
large files, using "newfs -b 32768" instead of the default settings
would speed up the process drastically.  Note that this might be
unfeasable because you already have data on the disk.

Another suggestion is to separate the volume into smaller slices, this
would reduce the impact.

BTW.  Our experience with a semi full 1.3T volume is that the snapshot
would take about 1 hour on FreeBSD 5.x, but I doubt that it is not
really comparable to your situation as the hardware is very different.

>  - How do I diagnose the reason why it is not terminating?

This might be somewhat complicated.  Check out the developers' handbook.

Cheers,
-- 
Xin LI <delphij at delphij.net>	http://www.delphij.net/
FreeBSD - The Power to Serve!

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