Date: Fri, 9 Feb 2007 17:49:11 +0200 From: "Clayton Milos" <clay@milos.co.za> To: "Artem Kuchin" <matrix@itlegion.ru> Cc: freebsd-stable@freebsd.org Subject: Re: What is a good choice of sata-ii raid controller for freebsd? Message-ID: <00b701c74c61$d7d24990$fe03a8c0@claylaptop> References: <00ad01c74b65$79db1710$0c00a8c0@Artem> <20070208094620.GA9599@rink.nu> <00a701c74b6e$7c3e4550$fe03a8c0@claylaptop> <20070208165224.GA35610@icarus.home.lan> <c7aff4ef0702080952i7abb4a4dpe15e2554019b815f@mail.gmail.com><004401c74c31$f8159160$0c00a8c0@Artem><45CC72D4.9040104@lxnt.info> <01e601c74c5d$31be19c0$0c00a8c0@Artem>
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----- Original Message ----- From: "Artem Kuchin" <matrix@itlegion.ru> 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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