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Date:      Thu, 28 Sep 2006 13:00:38 +0200
From:      "Chris Knipe" <>
To:        <>
Subject:   OT General, RAID and Drives
Message-ID:  <001b01c6e2ed$566edb30$0164640a@superman>

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This is just about the best mailing list that I'm subscribed to for this
discussion, and I believe this was in some extend covered before (SCSI vs.
SATA).  I'm looking at getting some storage put together.  At the moment, I
have about 800GB of Fiber Channels in a JBOD configuration (Posted
previously about this looking for Emulex Drivers in BSD).  For interest
sakes, it is running on Windows 2003 at the moment, as the only drivers I
found are for Windows and Linux based systems - nothing for FreeBSD as far
as Emulex goes.


Now, let's talk about Disk IO *only*.  I'm not too hecticly interested in
transfer speeds, as even PATA has more than enough speed as far as my
requirements go.  The applications that I intent to run on the storage
system however, will be MASSIVELY IO intensive.  We're talking LARGE files
ranging from 800MB to 50GB (per file), with various reads and writes inside
the files.  I am considering RAID3 for this with hot spares and the like.


Now, given that someone can shed some light on the IO issues, I'm happy to
get rid of all FC devices I have (3 x DAE's fully populated), and invest in
SATA or SCSI (which will also be significantly cheaper).  But, what kind of
IO can you expect from SATA on RAID3?


FC (which I have now), performs VERY well even with software RAID5 as far as
Disk IO goes.  From experience working with SCSI arrays, I know that SCSI is
also a pretty good choice for Disk IO.  SCSI is still however a tad
expensive.  Given a good PCIe 64bit SATA controller. What can be expected as
far as Disk IO goes??? 


Will I be safe in presuming that I will get reasonable (and with that I
mean, something that can be comparable to FC) IO out of such a system?  If
we're looking at 3TB arrays spanned over 7 or more disks, will it perform?
The costs of SATA is also much less than SCSI or FC, but the MTBF for SATA
seems to be something that is very much questioned in systems like this.
Given the cost factor of SATA vs FC, replacing disks on SATA seems to be
small change in comparison of what HBAs, FC Drives, and the link costs - so
that is also a risk I'm willing to take. 


Google is giving me very little results as far as performance goes when
comparing FC vs. SATA however. Anyone *please* some information on this??? 


Thanks allot,



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