[ale] SATA, iSCSI, and ESX

[James P. Kinney III]

On Tue, 2007-11-27 at 01:07 -0500, Ashley Wilson wrote:
> Forgive me if this is an absolutely stupid question... but is it possible to
> get decent performance out of an iSCSI SAN full of SATA disks backing an ESX
> server?  Has SATA advanced enough that it could be a reasonable (if somewhat
> lesser-performing) alternative to SAS or SCSI disks in an iSCSI SAN?  The
> VMs are dev only, but the SAN would have a built-in NAS feature hosting
> users' home folders.  Am I trying to do too much with too little?
> Thanks,
> -Ash 
> 

Ashley,
You can get some good performance from SATA drives if they are striped
in the array and the network connection is not crowded. SATA 300will of
course be faster. In fact, SATA 300 is about the same current sustained
speed as SAS drives (which are a slight tad under the highest SCSI
speeds). The absolute fastest performance will be in a NAS with a 10Gb
connection feeding a dedicated 10Gb/1Gb switch with a bank of SATA 300
drives in RAID0. 

Personally, I have sleeping issues using RAID0 so I prefer RAID10 (pairs
of RAID1 drives grouped in a RAID0 stripe). As the burst speed is 3Gbps
for SATA 300 and sustained is 300Mbps, the number of drives (and the
underlying bus joining them to the NIC) will determine the required NIC
speed. It may be also capable (if using a Linux systems as a NAS box) to
use NIC bonding to aggregate several 1Gb eth's to make a bigger pipe and
avoid the expense of a 10Gb connection setup.

Note: read the specs on the NAS motherboard carefully. Pay particular
attention to the block diagram and the SATA/SAS connectors location.
Many boards have those connections located bus wise such that there is
no advantage to a RAID0 stripe. In that case, look at an add-on card
that uses PCIexpress to get higher board throughput.
> 
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> 
-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC        
770-493-8244                    
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
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