Quoting David Jonas djonas@vitalwerks.com:
I've been considering getting a pair of SSDs in raid1 for just the dovecot indexes.
While raid-1 is better than the raid-0 of the previous poster, do you really want to slow down your fast SDDs with software raid-1 on top of them?
The hope would be to minimize the impact of pop3 users hammering the server.
Proposed design is something like 2 drives (ssd or platter) for OS and logs
The OS is mostly cached, so any old drive should work. Logs are lots of writes, so a dedicated drive might be nice (no raid). Be sure to tune the OS for the logs...
2 ssds for indexes (soft raid1),
I'd probably just go with one drive, maybe have a spare as a cold- or
hot-spare
in case of failure.
12 sata or sas drives in RAID5 or 6 (hw raid, probably 3ware) for maildirs. The
I'd say either raid-6 or raid-10 for this, depending on budget and size needs.
indexes and mailboxes would be mirrored with drbd. Seems like the best of both worlds -- fast and lots of storage.
drbd to where at what level? There was a some other discussion about this which basically said "Don't use drbd to mirror between VM guests" which I agree with. If you want to do this, use DRBD between VM servers (physical hosts) and not between VM guests (virtual hosts).
I do use a VM cluster with DRBD between the physical hosts, but not for mail services, and it works fine. Doing DRBD inside the virtual hosts though would not be good...
Does anyone run a configuration like this? How does it work for you?
No. I do 2 nodes, with DRBD between them, using GFS on them for both the mbox files and indexes... No virtualization at all... No SSD drives at all...
Anyone have any improvements on the design? Suggestions?
Only my advice about where to drbd if you are virtualizing, and what raid levels to use... But these are just my opinions and your milage may vary...
-- Eric Rostetter The Department of Physics The University of Texas at Austin
Go Longhorns!