[K12OSN] SATA vs SCSI

Chris Kacoroski ckacoroski at nsd.org
Mon Sep 20 18:10:29 UTC 2004


Liam,

I did several tests with SATA and SCSI and found out that the controller 
card is a limiting factor.  The fundamental difference between the two 
technologies is that SCSI drives queue up the requests and the optimize 
the path of the r/w head across the disk.  SATA do not have this ability 
so the r/w head wanders all over the disk handling the requests in a 
first come, first serve basis.

What this means, is that if you are reading or writing one large file, 
SATA perform as good as SCSI (if they have the same spindle speed).  If 
you have several different processes r/w to multiple files on disk, SCSI 
out performs SATA by a large margin.  The new SATA standard out sometime 
next year is suppose to include queueing, but until then SCSI is 
definitely worth it for small installations like yours.

If you have a large installation (e.g. 2TB+ of disk), you can use a 
device like the EonStor raid which connects SATA disks to a scsi 
controller and performs very well.  I have one of these and plan to get 
another one for a different application.  I tried 3ware cards, but they 
failed in my application (I still use them to mirror the system disks 
and they work great for that).

cheers,

ski

Liam Marshall wrote:
> this is my current hard drive situation, which will probably have to 
> stay until next year.
> 
> 1 - small regular ide drive for the system to boot off of.  I
> t holds the /boot partition and does nothing else
> 1 - 8 GB ibm SCSI drive, holding /root /usr etc
> 1 - 18 HB Seagate SCSI holding  /home /opt and the /swap partition
> 
> no raid
> 
> In an earlier thread, someone mentioned using SATA drives successfully 
> with a large number of users, 25+
> When I go to configure next years server(we will upgrade) can I use SATA 
> drives in a raid 0 configuration?  I want to increase performance hence 
> the raid 0, but heard that SATA drives might not handle a class of 25+ 
> workstations
> 
> any advice?
> 
> SATA is cheaper, I assume, than SCSI, so that would be a preferred path 
> if true
> 
> 
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-- 
"When we try to pick out anything by itself, we find it
   connected to the entire universe"		John Muir

Chris "Ski" Kacoroski, ckacoroski at nsd.org, 425-489-6263





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