On 16/04/2010 10:19, Mickael Lambert wrote:
First!
Great thanks for this great technology that is ZFS!
Then!
I need some advices about a weird thing I just find out.
Seems my I/O on a crypted zvol is 3 time more than the corresponding
ones off the pool on the lofi device.
I have attached a file containing all information I know about.
That should be very easy to reproduce.
Did someone could explain that behavior to me?
Encryption costs and in this setup you have multiple layers here too, a
ZFS pool ontop of lofi (doing the encryption) ontop of a ZVOL which is
in your rpool.
So any write to the filesystems in "apool" have to go to ZFS, then to
lofi (and be encrypted) then to the ZVOL that is in your rpool, that
alone without the encryption adds to the IO requirements.
A fair comparison would be to do the same setup with the multiple pools
and lofi but don't have lofi do encryption. That would tell you the
overhead of the encryption that lofi does.
--
Darren J Moffat
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