A beginner project

[Eric Anderson]

On 01/22/07 07:12, Ivan Voras wrote:
> Eric Anderson wrote:
> 
>> Not snapshot like a photo, snapshot like 'point in time copy of storage'.
>>
> 
> I think the "current" problem with geom-based snapshots is how will they
> interact with gjournal - i.e. do you snapshot the journal or not?

I think it only matters if you use UFS, if you care about a consistent 
filesystem on the snapshot.  You could probably tie a hook into geom 
snapshot to tell gjournal to flush the journal, take the snapshot, and 
then continue.  A similar hook (like gjournal has) to flush the buffer 
down to the disk would be good to have in geom snapshot also.

I actually think the hard part is keeping track of the snapshotted 
blocks, and keeping them in an order that doesn't completely destroy 
performance, while still allowing an 'instant' snapshot.  UFS snapshots 
take a very very long time on large file systems, so a geom snapshot (to 
be useful) should be snappy (pun intended).



Eric




-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
An undefined problem has an infinite number of solutions.
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