Adam Vande More amvandemore at gmail.com
Sat Sep 11 15:47:06 UTC 2010

On Sat, Sep 11, 2010 at 9:25 AM, RW <rwmaillists at googlemail.com> wrote:

> I'm planning to use gjournal+geli on a 2TB drive in a USB enclosure.
> What I've read about this suggest that the order should be:
> geli-gjournal-ufs. I was wondering if it's possible to do it in
> the order gjournal-geli-ufs, which should be much more efficient. I've
> read that ufs should go directly on gjournal, but I just wanted to
> check that that is needed.
> I was also wondering about the journal size, and whether there are any
> performance optimizations to be made to mitigate the extra
> encryption/decryption in the journal. The man page suggests a size of at
> least 2xmemory which would be 2x1.5GB now, or maybe 2x16GB to allow for
> potential upgrades. It seems very large. The disk will hold fairly
> static data so it will be mostly be long sustained writes as files are
> copied in. Currently coping from geli to geli with soft-updates is
> slightly cpu limited.

AFAIK, ufs must be on top of gjournal.  Specific changes were made to allow
ufs to be aware of the journal and I think sticking geli in-between would
destroy that relationship.

IME, gjournal is more sensitive to load as the man page also suggests.  I
have one production server with moderate load, and a 5 GB problem.  I think
something like 5 -10 GB journal would be more than enough for almost all
loads, but that's just a guess.  It's easy to test though, just run
blogbench or some other io benchmark for a sustained period of time.  If it
doesn't panic, you're golden.

Adam Vande More

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