Hardware RAID Level & Performance

[Rob Mueller]

> <http://www.synetic.net/Synetic-Products/SyneRAID-Units/SyneRAID6-16-3U/SyneRAID6-SATA.htm>
>
> No experience with them, but they're the best specs I've seen for SATA 
> external RAID - decent processor and NCQ support.

There's quite a few companies making these SATA-to-SCSI and SATA-to-FC 
boxes. A lot of them look quite similar and have almost identical specs, and 
are probably just rebadged versions of the same box made somewhere in 
Taiwan/China.

http://www.excelmeridiandata.com/products/raid.shtml
http://www.fibrenetix.co.uk/products/
http://www.infortrend.com/800600/eonstor.asp
http://www.areasys.com/template.asp?content=index_ide_raid.asp

I'm sure a bit of google searching can find a lot more.

They appear to be reaonsably good value, and some of them have some nice 
features:

1. High density - eg. 12 400G SATA drives in 3U is a lot of space
2. RAID6 - some units now have what they call "RAID6", which is RAID5 with 
double parity. That's different to RAID5+hotspare in that 2 drives can fail 
simultaneously with no problems. Nice if you have high IO load situation, 
since if 1 drive fails, and you wait for it to rebuild to the hotspare it 
could be 24+ hours, quite a danger time for another drive to possibly fail 
in a big 12 or 16 drive array.
3. All-in-one - Sure you could have a PC motherboard and SATA controller 
card and an appropriate, but then you've got another OS to maintain/upgrade, 
etc. These tend to come as one box that you slide the drives in, create the 
partitions through a web-interface, and away you go. They often offer 
monitoring via a web-interface, and active alerting through SNMP and/or SMTP 
email.
4. Battery backup - most of them come with 128M-1024M of cache, and an 
optional battery backup option so you can use write-back caching which 
definitely helps performance

Areasys include a blurb why they think it's better than a "build your own" 
solution, but of course make up your own mind.
http://www.areasys.com/pdf/2012_vs_HomeMadeStorageServer.pdf

We've used two different boxes from different companies and so far they've 
worked great. Hmmm, hope I'm not tempting murphy by saying that... ;)

Rob

---
Cyrus Home Page: http://asg.web.cmu.edu/cyrus
Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu
List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html