On 2012-11-21 03:21, nathan wrote:
Overall, the pain of the doubling of bandwidth requirements seems like a
big downer for *my* configuration, as I have just the one SSD, but I'll
persist and see what I can get out of it.

I might also speculate that for each rewritten block of userdata in
the VM image, you have a series of metadata block updates in ZFS.
If you keep the zvol blocks relatively small, you might get the
effective doubling of writes for the userdata updates.

As for ZIL - even if it is used with the in-pool variant, I don't
think your setup needs any extra steps to disable it (as Edward likes
to suggest), and most other setups don't need to disable it either.
It also shouldn't add much to your writes - the in-pool ZIL blocks
are then referenced as userdata when the TXG commit happens (I think).

I also think that with a VM in a raw partition you don't get any
snapshots - neither ZFS as underlying storage ('cause it's not),
not hypervisor snaps of the VM. So while faster, this is also some
trade-off :)


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