Re: SATA vs SCSI RAID 5?

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To: freebsd-isp@freebsd.org
Date: Tue, 11 Jan 2005 11:15:48 -0800

On Tue, 2005-01-11 at 13:50 -0500, Gerald wrote:
> I recently setup a SATA RAID1 box on a highpoint controller. The
> machine is playing very nicely with FreeBSD and doing much better than
> I initially expected. Now I'm considering upgrading a SCSI system to
> another SATA RAID 5 system.
>
> Can anyone tell me about SATA RAID 5 experiences? The company I'm
> looking at purchasing this from is using the Highpoint R1820 controller.

I not sure about the newer SATA RAID controllers, but I know CPU usage
was way higher on all SATA RAID controllers than on SCSI RAID
controllers like those from Adaptec. Good SCSI RAID controllers offload
a lot of the computation from the host machine onto the card itself.

> SATA= "putting the 'I' back in RAID" or "magic 8 ball says, 'Ask again
> later."?
>
> For reference on the decision making, the present machine is setup on an
> Adaptec 3200S with all but one of the partitions as RAID1 and the last
> one as RAID5. All the drives in the present system are SCSI SCA 10k RPMs
> I believe. The machine is primarily an apache 1.3/freeBSD 4 web server
> doing 25-30 MB of web traffic at peak 17-20 MB on Average.

For a webserver, you might not notice much of an impact by switching to
an SATA controller, not like you would on a busy database server,
because the webserver might not be hitting the disk IO very hard.

If you decide to switch to SATA RAID, myself and probably at least a few
others would be interested in seeing what difference this makes in CPU
usage and server load.

If the SATA RAID controllers mature to the point of matching the low CPU
usage that expensive Adaptec cards attain, then they might finally be
able to overthrow SCSI in the server market. The performance is already
there, but the high CPU usage for past SATA controllers would cripple
servers where a high load is noticeable and annoying to users, such as
in the VPS hosting segment.

-- 
Justin Hopper  <jhopper@bsdhosting.net>
UNIX Systems Engineer
BSDHosting.net
Hosting Division of Digital Oasys Inc.
http://www.bsdhosting.net
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