linux pageouts

[Martha Mueller]

I am confused about pageouts on linux. We have a linux server running Red Hat 5.5. uname -a returns "2.6.18-238.5.1.el5 #1 SMP Mon Feb 21 05:52:39 EST 2011 x86_64 x86_64 x86_64 GNU/Linux". It has 48 GB memory.

When I run the command sar -B, the average pageouts per second is 361. When I run the vmstat command, the "so" value is zero. I have read that the vmstat value for "so" - swapout, is the same thing as pageout, yet I get two very different values using these two commands.

In linux, should we expect that the pageout value is normally this high? I am used to having pageouts less than 10, not in the hundreds. Or does linux pageout include things like writing data to raw logical volumes? We run Sybase on this query server, so there shouldn't be a huge number of writes, mostly reads. But there are no filesystems on the data drives, it is raw logical volumes.

Thanks

[dirk dierickx · Accepted solution]

When checking the man page, you'll notice that the 'majflt/s' collumn is the one you want to be looking at. this one defines paging with disk IO involved, you don't want this.

[Martha Mueller]

Thank you