----- Original Message -----
From: "Artem Kuchin" <[EMAIL PROTECTED]>
To: <freebsd-stable@freebsd.org>
Sent: Friday, February 09, 2007 5:15 PM
Subject: Re: What is a good choice of sata-ii raid controller for freebsd?
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?
--
Artem
I set up 3 RedHat Enterprise servers in a cluster for a customer 2-3 years
ago. Dual P4-XEON 3.4GHz with 16G of ram each.
Really lovely servers. Intel server motherboards with 2 x15k RPM SCSI drives
as a mirror for the OS and fibrechannel external storage for Oracle 10i.
The SCSI RAID on the motherboard was horrifically slow. I'm talking around
5MB/s hardware raid for 15k RPM SCSI drives. Turns out it was a known bug on
the Intel motherboards with no workaround or fix so I set the boxes up with
Linux software raid. The performance was excellent and they are still
running perfectly today. I think the SCSI controller was Symbios or
something like that.
Ever since then I have not trusted Intel and RAID in the same sentence. I
was really upset that they were not interested in fixing the issue. I even
emailed Intel to ask them about it and they said there was not much
likelihood of a fix.
Call me biased but that's just what my experience has taught me.
Btw the Areca cards have Intel RISC CPU's on them and they are lightning
fast.
-Clay
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