GEOM_JOURNAL on a 550G partition - opinions ?
Hugo Silva
hugo at barafranca.com
Wed Feb 4 09:29:34 PST 2009
Hi list,
For a server I will be setting up, I am considering using gjournal on
the partition that will hold all the www data.
The journaled partition (mounted async) would be mostly read from,
uploads would not be very frequent and most sites wouldn't write to the
disk. Logs would be kept elsewhere.
This server will have two hard disks, mirrored (gmirror) at the disk level.
Here are my questions:
- Will the fact that gmirror is underneath the journal
(/dev/mirror/gm0s1f.journal) affect performance ? (either positively or
negatively)
(* I would be keeping the journal in the same provider)
- Would reads / writes be faster? considerably faster ? (gjournal) I've
seen different numbers from different places, the impression I got is
that reads should be faster while writes will be substantially slower -
is this correct ?
- What about reliability ? From the manpage, I know that if I journaled
the entire mirror, I would not need to sync it after an unclean shutdown.
Going from the assumption that this will not be so for a single
journaled partition, will there be any interference between gjournal and
gmirror ?
- I've never had an UFS2 partition filled with more than 200G of data,
so I am not sure what to expect for 550G with soft-updates (I expect
this partition to hold close to 550G of data) - real numbers about this
would also be helpful.
Any personal experiences concerning gjournal or gmirror+gjournal are
greatly appreciated!
Thanks.
Hugo
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