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[Port25-Admin1]

https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/newmds-ssdtuning.html

Red Hat also warns that software RAID levels 1, 4, 5, and 6 are not recommended for use on SSDs. During the initialization stage of these RAID levels, some RAID management utilities (such as mdadm) write to all of the blocks on the storage device to ensure that checksums operate properly. This will cause the performance of the SSD to degrade quickly.

[rg]

I know logically this doesn't make any sense, but we have seen some pretty dramatic increase in performance when reconfiguring our SAN Array in RAID5 compared to 10. I know, again, the theory is just the opposite but practically it runs better for the load that PMTA has.

We are currently running on dedicated RAID5 SSD Array with Intel X7 series for queueing and on SAS SAN with RAID 5 for logging and accounting files.

Hey @teneo  - I felt raid 5 was helping on old server... but after 2 disk failure on the old server, I am bit reluctant. On the new server... i still wanted to stay at raid 5 but with more reliability... hence the raid 50. What I am seeing from @calvin and other posts that raid 10 is worth looking into.

[sackley]

I just wanted to put a note in for historical purposes.   I configured 2 RAID arrays, both RAID10 (4 disks each).   I use one array with SSD for the OS drive and 1/2 the spool, and then 15k SAS for the second array and the other 1/2 the spool (a second spool).   With PowerMTA v4 and the new queue mechanisms, if we ever get too much mail on the SSD's it will automatically spill over onto the SAS drives in realtime.

I found that using the Adaptec 6805 with those 8 drives, and 16 gigs of RAM really works wonders, and killer performance.   We have 6 x /24 subnets on the machine, but we have a farm of many more machines all networked together using a load balancer.