Re: a heavy duty operation on an "unused" table kills my server

Matthew Wakeling wrote:
> On Thu, 14 Jan 2010, Greg Smith wrote:
>> Andy Colson wrote:
>>> So if there is very little io, or if there is way way too much, then 
>>> the scheduler really doesn't matter.  So there is a slim middle 
>>> ground where the io is within a small percent of the HD capacity 
>>> where the scheduler might make a difference?
>>
>> That's basically how I see it.  There seem to be people who run into 
>> workloads in the middle ground where the scheduler makes a world of 
>> difference.  I've never seen one myself, and suspect that some of the 
>> reports of deadline being a big improvement just relate to some 
>> buginess in the default CFQ implementation that I just haven't 
>> encountered.
> 
> That's the perception I get. CFQ is the default scheduler, but in most 
> systems I have seen, it performs worse than the other three schedulers, 
> all of which seem to have identical performance. I would avoid 
> anticipatory on a RAID array though.

I thought the best strategy for a good RAID controller was NOOP.  Anything the OS does just makes it harder for the RAID controller to do its job.  With a direct-attached disk, the OS knows where the heads are, but with a battery-backed RAID controller, the OS has no idea what's actually happening.

Craig