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Re: How does one size a HN? Is RAM or CPU more important? [message #10544 is a reply to message #10538] Wed, 21 February 2007 11:27 Go to previous messageGo to previous message
rickb is currently offline  rickb
Messages: 368
Registered: October 2006
Senior Member
Thank you for the information, truly a valuable post. I have some further questions if you have time.

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What sector readahead value are you using with blockdev? Default on my card is 256 (blockdev --getra /dev/sdX), the pdf suggest 16384 secs.

I am using ext3 but am not using any tuned values beyond noatime. Have you found and performance gains from optimizations on the fs level?

I am using the cfq io scheduler, because after reading and unofficially testing it, it seems to deliver the best io response time for a shared resource system. Although deadline may offer better overall io performance, fairness is more relevant in a shared resource environment. What are your thoughts on this?

My servers with this card have 8GB of ram, and I have created 8GB of swap; after 63 days of uptime, the system stays constant with ~2.5GB of swap utilized. I have read that adjusting the amount of swap in the system can positively effect performance. Do you have any ideas there?

[root@gallium ~]# free -m
total used free shared buffers cached
Mem: 8029 8004 24 0 97 1586
-/+ buffers/cache: 6320 1709
Swap: 8000 2609 5391


My primary indicator of "disk performance" in a shared resource environment is a (lower) iowait value over time (vmstat, sar, iostat, etc). Do you find this relevant?


-Rick Blundell



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[Updated on: Thu, 22 February 2007 02:50]

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