gjournal, hardware raid, software raid

Oliver Lehmann oliver at FreeBSD.org
Wed Sep 23 16:30:30 UTC 2009


I'll have soon the following System configuration:

two 250GB harddisks (WD2500KS)
 - configured as RAID1 using gmirror
 - disks are attached to a Promise SATA300 TX2plus
 - are supposed to hold the whole base system+swap

four 1TB harddisks (WD10EADS)
 - configured as RAID5 using a 3ware 3500-4LP with a
   battery backup unit having write cache enabled.
 - will hold one big (around 3TB) partition using GPT

The system itself has 2GB of RAM and is an old dual PIII 850 running on
an intel L440GX+

I now plan to setup gjournal for the 3TB partition to slow down the fsck
run times. The system crashes from time to time so this is vital for me ;)

I thought about what would be the best configuration here and I saw 3

1) have one partition on the 3TB RAID sharing data and journal
2) have two partitions, one holding the journal, one holding the data.
   Both on the 3TB RAID. Preferable the journal at the "beginning" of the
3) same partitions like above but the journal partition will be on the
   gmirror RAID1 holding the base system.

I like the 3rd option because on a heavy I/O load on the RAID5 the 3ware
must not switch between data and journal and can stick to handling the
data only. The Promise controller will then stick to handle the data.
Looks like some I/O balancing for me...

I maybe want gjournal for the /usr partition of the RAID1 as well. So I
would then have two 6GB (2GB*3) journaling partitions on the RAID1 if I
go for option 3.

What do you guys think.

Please keep me CCed - I'm not subscribed.

 Oliver Lehmann

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