On 02/08/2012 07:00 AM, Ori Mamluk wrote:
Hi,
Following previous mails from Kevin and Dor, I'd like to specify the high level
requirements of a replication agent as I see them.
1. Report each write to a protected volume to the rephub, at an IO transaction
granularity
* The reporting is not synchronous, i.e. the write completion is not delayed
until the rephub received it.
* The IOs have to be the raw guest IOs - i.e. not converted to any sparse format
or another filter that alters the size/offset
For now. I'm sure you'll eventually have a synchronous replication requirement.
We're doomed to reinvent all of the Linux storage layer it seems. I think we
really only have two choices: make better use of kernel facilities for this
(like drbd) or have a proper, pluggable, storage interface so that QEMU proper
doesn't have to deal with all of this.
Gluster is appealing as a pluggable storage interface although the license is
problematic for us today.
I'm quite confident that we shouldn't be in the business of replicating storage
though. If the answer is NBD++, that's fine too.
Regards,
Anthony Liguori
