[ale] raid suggestions

[Pat Regan]

On Wed, 15 Feb 2012 09:44:22 -0500
"mike at trausch.us" <mike at trausch.us> wrote:

> I have a RAID 6 array that is somewhat slow, but I know _precisely_
> why it is slow and it has nothing to do with the kernel; the
> bottleneck in this case is the SATA port multiplier, and without
> spending a little more money there is nothing that I can do about it.

Since we're speaking about corner cases and odd hardware problems...

I've been using the same motherboard in my home file server (aka, my
arcade cabinet these days) for 4-5 years.  It has 6 SATA ports and
started life with a 4 drive RAID 5.  Performance was still good when I
added a 5th drive.  Adding a 6th drive didn't go so well...

The initial resync took forever and read speeds plummeted to about the
speed of a single drive.  Usually read speeds go up as you increase
drive count and fresh write speed stays pretty constant.

I didn't really care about the performance at the time, it usually only
had to keep up with my 100 megabit switch or my wifi.  The problem did
straighten itself out at some point, though, during a kernel upgrade.
I'm assuming the problem was some sort of driver inefficiency.

Pat