[mythtv-users] Question re: available SATA ports and linux software RAID

[Ian Clark]

On 7 April 2011 11:47, Alex Butcher <mythlist at assursys.co.uk> wrote:
[snip]
>
>>> HOWEVER... many of the chipsets used on cheap SATA controllers are buggy:
>>>
>>> <http://codemonkey.org.uk/2009/01/20/sata-disasters-silicon-image-3114/>
>>> <http://marc.info/?t=123089876500001&r=1&w=2>
>>> <https://bugs.launchpad.net/ubuntu/+source/linux/+bug/263160>
>>
>> Something plugged out of the blue obviously, and certainly a one-off
>> occurrence.;
>
> Those are seperate reports, and the SiL3114 and VT6421 are very popular on
> the cheap SATA cards I find for readily available in the UK. Furthermore,
> codemonkey.org.uk is Dave Jones' blog. Dave is one of the kernel devs, and
> has worked for SuSE and Red Hat.
>
FWIW I've found the Sillicon image based cards somewhat problematic
too. I had one I inherited off a friend (works fine), because he
couldn't use 2 of them in the same machine without serious
reliablility issues. (This was using linux, but as I understand it was
a hardware limitation.)

I wanted to use it to support 8 drives in my server last time I was
moving RAID arrays about, and found that with all 6 ports onboard (AMD
780G chipset) populated and that card plugged in I was unable to get
the system reliable. On the odd occasion I could get the machine to
boot the OS would hang very early in the detection code when all the
SATA ports were populated (admittedly this was NetBSD, using AHCI, but
still)

Just be aware if combining cheapo SATA cards, when things get full
they tend to get a bit flaky (Most of these are very cheap units used
to add SATA to old machines that didn't have it, rather than for being
used in full and heavly loaded systems.)

Oh, and it's also worth remembering that for RAID5 you should ideally
have a number of drives that's a power of 2 plus 1, this should be a
power of 2 plus 2 for RAID 6 (so a raid5 array is ideally 3 drives, 5
drives, 9 drives etc etc)

Cheers,

Ian