help configuring a db server

Tim Small tim at seoss.co.uk
Thu Feb 11 11:38:51 CST 2010


John G. Heim wrote:
> But I'm confused about disk. I would think disk pspeed 
> would be fairly important.

That entirely depends on your database usage pattern:

What is your total dataset size?
What is your working set (i.e. data which is commonly/regularly accessed)?
Can you reasonably fit your working set into RAM?
What is your read/write ratio (i.e. select vs update/insert)?

If at all possible, aim to have enough RAM for your working set, if you 
can't then disk speed becomes important for read performance.
Write latency (time taken to commit to permanent storage) is critical if 
you are doing a lot of writes - in this case getting a RAID controller 
with battery-backed cache is a win - otherwise it probably isn't.

So... if you have a database (or databases) with a working set of 10G, 
and a high read:write ratio, then disk performance probably isn't going 
to be important.

Another hint (excuse if you know this stuff already), but you can very 
readily get large performance improvements by optimising your mysql  
server config (e.g. using mysqlanalyze, and this munin plugin: 
http://github.com/kjellm/munin-mysql/downloads )


Tim.

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