What is a good choice of sata-ii raid controller for freebsd?

Artem Kuchin matrix at itlegion.ru
Fri Feb 9 15:16:01 UTC 2007

Alexander Sabourenkov wrote:
> Artem Kuchin wrote:
>> hi!
>> I am the original poster of this thread. I have read many interesting
>> reply during these two days. However, as i said in the original
>> message due to certification issues i am pretty limited to INTEL
>> controllers  and i have not seen a single relevant reply about them.
>> This is interesting. Nobody uses Intel controllers on FreeBSD or
>> they just suck that much?
> If you have enough  SATA ports and no need for fancy RAID levels,
> then my advice is to use gmirror.
> Hardware RAID1 buys you nothing in perfomance and reliability
> for a prolonged headache with drivers, bios insanity and
> monitoring+control tools.

Hm... two points here. I, somehow, do not really believe that
software raid (gmirror for example) is as reliable as hardware.
I, deeply inside, believe that i might screw things very badly under some
heavy load and bad timing conditions. Can't explain it. it is religious i guess,
but i can be very wrong about this.

However, two perfomance point:
Under gmirror OS must issue two commands to write to disks and some
commands to check/set mark that mirrored data is intact.
Under hardware RAID OS issue sonly one command to write and no
checking command, since raid controller handles this async.

So, software OS raid must be slower than controller based raid anyway.

Am i right here? Any benchmark data on this?

As for reliability of gmirror. I just need to know how it works to see
for myself that if power turned off in some racing condition gmirror will know that
disk are out of sync. If it is done than gmirror must check sync of disks every read, and
that mean two command for reading too, which must slow down things.
Is it true?


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