[CentOS] Re: Native Command Queueing

Scott Silva ssilva at sgvwater.com
Thu Jul 24 23:42:11 UTC 2008


on 7-24-2008 4:21 PM Matt spake the following:
>>> I was monitoring it with SAR and there was very high level of IOWait, meaning the drive was having a hard time.
> 
> How bad does the below look?  Dual core AM2 5600+ with 4G DDR2 and
> single SATA2 drive.
> 
> Matt
> 
<snip>
> 
> 05:40:01 PM       CPU     %user     %nice   %system   %iowait     %idle
> 05:50:01 PM       all      7.20      0.00      2.49      5.08     85.23
> Average:          all     14.13      0.00      3.12     14.85     67.90
User and IOwaits are a little high. Not going to stop the server, but it stops 
it from hitting its full potential.
How many users?
I have a server with about 80 users and my averages are;

Average:          all      6.00      0.00      3.65      3.95     86.40
That is with 2 dualcore XEON's at 2.2 Gh and 4 gigs and a SATA raid 5 (3ware)..
It was on a single drive for a month or so after a recovery and I had IOwaits 
like yours. System was sluggish. Users whined. It wasn't pretty. The single 
drive was the fastest recovery while I had to replace some drives that tanked. 
I have a spare, but not 3.



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