running mksnap_ffs

Willem Jan Withagen wjw at withagen.nl
Thu Jan 4 05:04:31 PST 2007


LI Xin wrote:
> 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.

Well the disk is loaded with very different types of files....
It is my home file server and contains 10 years of Email in Mailbox/ format, 
al types of development work, my complete ripped CD collection (and more), 
next to that I've started to see how I can networkstream my DvD collection.
So it depends on what you call a large file. :)

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

I always seem to make the wrong sizes, run out of space, and start to symlink.
Which drives me completely crazy. So this time I went for one big slice, but 
makeing backups now starts to become a serious point of attention. :~}

> 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.

Can you give me an idea of what type of HW you're running. So I can guestimate 
from there on. This means that you don't have access to the volume for about 1 
hour?

>>  - How do I diagnose the reason why it is not terminating?
> 
> This might be somewhat complicated.  Check out the developers' handbook.

Done that, but mucking on a system that important makes me hesitate. Although 
not being able to make backups nerves me too.

--WjW



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