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Re: [linux-lvm] Re: [RFC] Multiple Snapshots - Manageability problem

Dan Kegel schrieb:
On Jan 23, 2008 8:16 AM, Tomasz Chmielewski <mangoo wpkg org> wrote:
Vijai Babu Madhavan, Thu, 11 Jan 2007 11:18:13 -0700, wrote:

The problem of DM snapshots with multiple snapshots have been discussed
in the lists quiet a bit (Most recently @

We are currently in the process of building a DM snapshot target that scales
well with many snapshots (so that the changed blocks don't get copied to each
snapshot). In this process, I would also like to validate an assumption.
Any news on that?

Still, with multiple snapshots write performance degrades linearly - is
any work done to change that anytime soon?

Yes.  Dan Phillips has implemented a shared snapshot exception store.
You can try it out now if you like; it's at http://zumastor.org.
It feels a bit different from the user's point of view than LVM, though.
It plays well with the device mapper and can be used with any
block device (LVM or non-LVM).

Does it use device mapper (or it just "plays well with the device mapper")? Or is it a totally different technology?

I didn't find it explained very clearly in Zumastor HOWTO on http://zumastor.googlecode.com/svn/trunk/doc/zumastor-howto.html (other than pointers to /dev/mapper/zumatest, which probably means it uses device mapper).

Tomasz Chmielewski

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