[TriLUG] Linux Software RAID experience

[Ron Kelley via TriLUG]

Greetings all,

Looking for some feedback with Linux software RAID.  I have a couple of
servers in a lights-out facility running LSI RAID controllers (2208 chips)
that have been working great for a long time.  Recently, we decided to
switch out spinning disks for SSDs (8x Samsung 1TB in RAID-5).  After
getting the RAID volume rebuilt, I noticed slow write speeds (about
500MB/secs).  I was expecting at least 1,500MB/secs writes given we have 8x
SSDs.  No amount of tuning/tweaking the RAID controller seems to make a
difference.

At this point, I can either purchase better/faster RAID controller
($500-$700) or switch over to Linux software RAID.  My past experience with
mdadm left me a little disappointed.  The RAID rebuild times were slow and
drive swaps were klunky (even after setting speed_limit_min and
speed_limit_max settings).  At one point, the build/rebuild speeds seemed
to cap out around 250MB/sec - even with SSDs.

I know mdadm has been around for a very long time, but I am looking for
some recent usage using mdadm on systems with SSDs.  What tool do you use
(Rockstor, FreeNAS, etc) to manage the RAID array and what kind of
performance do you get?  How "turn-key" is it to recover data or replace
drives?

At the end of the day, I need a turn-key RAID solution - easy enough that
someone can walk into the facility and replace a faulty drive w/out having
to dive into a CLI or use a management tool.


Thanks,

-Ron