Dominik Schulz put forth on 2/16/2010 3:33 AM:
Am Dienstag 16 Februar 2010 06:42:57 schrieb Wayne Thursby:
We are transitioning other services to high availability, and I'm wondering exactly how to provide some kind of near-realtime failover for my Postfix/Dovecot machine. The MD-1000 provides nothing in the way of iSCSI, but it *does* have two SAS connections available, only one of which is in use.
Keep away from the MD-1000/3000 stuff unless you're running SLES or RHEL.
One quick thing to add: The two ports on the MD-1000 are there for two reasons. You can split the backplane into two halves. One panel connector then services 7 drives on one side, the other connector services the other 7 drives.
This allows two separate hosts to control 7 drives each, one port/cable to each host.
You can connect two RAID controllers on one host to 7 drives on each controller. This config is meant as an optimization technique for extremely high bandwidth applications, specifically such as those requiring RAID5 in which case a single RAID controller may run out of internal parity processing power before maximizing disk throughput, having the disks running at less than maximum capacity. Another scenario is RAID0 (striping) across 14 fast drives overwhelming the throughput of a single RAID card. Again, splitting the drives across two cards can help alleviate this problem.
-- Stan