[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [linux-lvm] LVM 0.8final for 2.2.15/2.2.16?



And thus it came to pass that Paul Jakma wrote:
(on Thu, Jun 08, 2000 at 12:49:53PM +0100 to be exact)

> On Thu, 8 Jun 2000, Andi Kleen wrote:
> 
> > consider a database that uses user space journaling using fsync:
> > to make its disk files consistent after the snapshot it requires
> > both the log write and the data write. When one is missing the
> > log needs to be replayed, which requires writes.
> 
> but doesn't the call to block_fsync that Heinz confirmed exists cover
> this?
> 
> nothing can cover the case where app data consistency depends on a future
> write(). But that's the app's problem, and anyway a good database should
> be consistent/recover itself if it's died between write(?)'s. right?
> 
> (in which case lvm snapshot is perfectly suitable for backing up
> databases..)

Most databases want you to store their log and data spaces in different 
(logical) volumes. To create a consistent image you would want to be
able to snapshot multiple logical volumes atomically in one operation.
HP's LVM supports this through the "multiple atomical lvsplit"
feature (as of HP-UX 10 if memory serves me right).

++Jos

-- 
The InSANE quiz master is always right!
(or was it the other way round? :-)


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]