Re: [tlug] Disk I/O bottleneck: how to solve?

["Jean-Christian Imbeault" <jean_christian@example.com>]

>From: "Shimpei Yamashita" <shimpei@example.com>
>
>Are the log files on a different physical disk and bus from the files
>Apache is serving? You definitely don't want those on the same disk;

No, unfortunately they are on the same disk. I do want to move them over. I 
was just hoping that using more RAM as a disk buffer would help in the 
meantime.

Also I don't know how to measure if the problem is from too much writing or 
too much reading. All I can say is that the server writes out 1Gb in logs 
and gives out 20Gb in HTTP requests.

So from those numbers I tought the problem was from too many reads, not 
writes.

>BTW, Linux does use free memory to buffer disks, out of the box.

That's what I have been finding out. I read that Linux should use all the 
free memory it need or can get it's hands on as disk buffer. But if this 
were true I shouldn't be seeing 200M of free RAM all the time ...

>200M of free RAM isn't going to help you much
>with logging anyway;

True. I was hoping it would help with reads.

I am hoping there is some kernel setting that will cause Linux to use more 
RAM for buffering disk reads. I don't care (actually don't want) the writes 
to be buffered.

Maybe there is no such setting?

Jc

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