[Dovecot] Highly Performance and Availability

[Stan Hoeppner]

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.

1.  This allows two separate hosts to control 7 drives each, one port/cable to
each host.

2.  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