Jim Perrin wrote:
Would you mount all filesystems noatime, or just those that would
have any effect on operation?
No. I usually only do this on partitions I share out over smb/cifs
where I don't trust windows access timestamps anyway, or on
filesystems where I don't care when the last time a file was accessed
was (webroots, stuff like that). Mounting with noatime simply tells
the filesystem not to update data/metadata to account for file access
times. This saves a few cycles here and there, and can add up
depending on how often something gets hit.
> After that I move to /etc/sysctl.conf and tweak the kernel.shmmax,
> shmmin, shmall, and vdso values depending on the application I'm most
> concerned about, as well as fs.file-max.
Any hints on what to look for to determine the best settings?
Not really. Most of the apps we use here (oracle and netegrity stuff)
have tuning recommendations in the documentation or associated
kb/forums so I benchmark, change stuff to meet their recommendations,
benchmark again, and use whichever tests better. It's mostly a trial
and error kinda thing.
I suppose, without having extensive knowledge about how the model
behaves internally, or for that matter, writing to disk, it really would
be trial and error. There are tools, but I'm not experienced enough to
know what they are really telling me either. I know the model does a
lot of reads from data, but don't know if that data is cached on read,
or if the whole file is read in at once, then the numbers are crunched
and written or what.
According to that article, I might be better off staying with the CFQ,
but since this is a number crunching thing, I really don't know what to
look for, or where to look to see what really is going on behind the
monitor. I'm not savvy enough to know what the numerical model really
does in the background is what I'm trying to say. Any suggestions, or
could I provide more info that might help you help me?
Yeah, much of what I do here is webhosting/filehosting type stuff, so
for me disk tuning is my performance limiter. I was hoping some other
individuals would offer other performance tips after noticing that my
advice was very heavily disk oriented. I'd be interested in hearing
what other people are doing for performance tuning, but it seems like
the vast majority of people simply leave the defaults and don't mess
with things.
I've posted some questions to the WRF-model.org website so maybe one of
the developers or someone with extensive software background info will
respond. I know a lot of the weather oriented people who run the model
have little to no clue about unix or linux in general, just based on the
questions I see posted.
Sam
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