December 20, 2006 at 8:47 am
Hi All,
I am putting together a requirement specification for the purchase of a high performance SAN storage device.
At the moment, my configuration is on a RAID 5 config, but because of performance I am planning to move onto a RAID 10 config, I was wondering, in terms of disk specification, I am not worried about cost, all I am after is bruising performance.
Any ideas ?
I have been looking on the forums, and I have come up with the following incomplete specs, Please feel free to suggest as much specifications as possible, along the lines below
SAN Sample Specs
Controllers 2
Disk capacity 700 GB*; 7,200 RPM SATA II
Number of drives 15
I/Os per second 60,000
Gb network interfaces 3
Copper (standard)
Optical (Optional)
December 20, 2006 at 11:43 am
Deploying SQL Server 2005 with SAN
http://blogs.msdn.com/sqlcat/archive/2005/10/11/479887.aspx
MohammedU
Microsoft SQL Server MVP
December 20, 2006 at 2:34 pm
Any reason why you wouldn't use 10k or 15k rpm drives instead of 7200 rpm's except the cost?
December 20, 2006 at 5:22 pm
Hey John,
We've currently got SAN installed at our office and to tell you the truth, havn't seen much of a difference.
In regards to your question about RAID - the one that we intstalled has RAID-DP on it - per the vendor, the highest in performance and with dual parity.
About the disk space - Ask the vendor about the usable disk space, as about 1/3 of the disk space gets used for SAN operations. On top of that your specifications of usable disk space needs to incorporate the number of snapshots you want to keep - a week or day's worth* no. of shapshots taken per day/. eg: if a database is 2 GB, you might have to allocate nearly 10GB worth of volume space to keep a week's worth of snapshots. and yes, it also depends on the rate of change of data in your database.
Also, its better to go with Fiber optical channel than with ISCSI as fiber gives you 1 GB compared to ISCSI that has only 512 or so.
Also, when you install SAN, look at all the reasons for why you actually need it. The best use of SAN is that you are able to SNAP Mirror your data to anywhere very quickly. Here again, you need to consider the rate of change of all data and the link speed between 2 sites (if your DRP site is somewhere else).
I'm telling you what I've learnt from my experience. Its more to help you think about all aspects of SAN before purchasing anything.
Hope this helps.
December 21, 2006 at 4:59 am
sata disks will not give you the performance of scssi disks for random i/o, however as you're only specifying 15 spindles it's more of an external raid array.
Raid 5 is fine for reads but rubbish for writes, raid 10 is best all round .. double parity ( or raid 6 ) is as bad as raid 5 and a marketing ploy to attempt to improve reliability. Basically for each additional spindle in a raid 5 array the risk of failure ( as a mathmatical fomula ) increases, whereas for raid 10 the risk is static and doesn't change as you add more disks, raid 6 only adds an extra parity disk so the gain is minimal. Raid 5 and raid 6 are used to leverage the maximum usable capacity from a storage array at the expense of write performance.
1gb iscsi = 1gb fc , but most fibre channel is 4gb now, there is 10gb ethernet and 10gb fc promised for next year , with some 8gb fc available now(ish ) I believe.
Don't believe a SAN will be faster, it often isn't, Tony Rogerson had some SAN issues, check out his blog here http://sqlblogcasts.com/blogs/tonyrogerson/default.aspx
btw .. a SAN isn't a piece of hardware - it's a network fabric including storage elements.
[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/
December 21, 2006 at 6:07 am
thanks all for the reply, the SAN will be primarily for storage, but these days you cant seem to get Storage and Performance, there has to be a trade off, thats why RAID 5 is so popular.
I am after a fast and powerful SAN, so even if the ethernet speed increases to 10GB, because everything else has a limit of 1GB, so I still cannot get the performance boost by mere changing network speed..
Guys, so which is the best now IScsi or the FC ?
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