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measure

Member

Registered: 2009-07-17

Posts: 62

Directories with high IO

I recently purchased a Thinkpad x40, and I plan to put a dual compact flash adapter in it.  Specifically, with one fast 8gb master and one slower 4 or 8gb as the slave (just for safe measures).

My question is pretty simple: which directories should absolutely be on the faster card and which could comfortably sit on the slower? For example, I'd  be a fool to have /usr/* on the slower!

I know I am being a bit cautious as on a minimal system, you don't really even need 8gb, but I'd like to at least have this information available if the issue ever comes up.

Thanks,
Ryan

Wintervenom

Member

Registered: 2008-08-20

Posts: 1,011

Re: Directories with high IO

You would want /usr and /var on the faster device, for sure.

Last edited by Wintervenom (2010-04-08 17:22:17)

Runiq

Member

From: Germany

Registered: 2008-10-29

Posts: 1,053

Re: Directories with high IO

/dev, /proc and /sys should be on the faster one too, right? I mean, they're dynamic and (partly) automatically populated, after all…

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Dotfiles

pseudonomous

Member

Registered: 2008-04-23

Posts: 349

Re: Directories with high IO

Now, depending on the actual specs of the cards you get this will vary, but a lot of medium/slow compact flash has much faster read speeds than its write speeds, so it might make sense to put directories that are mostly read only on the slower device; /usr is mostly read, while /var and /tmp have way more writes; home also probably will have a lot more writes then /usr.  /usr should mostly change only when you're installing/uninstalling/upgrading packages.

On the other hand, you'll still read faster from the "fast" device than the slow device; it's just that the slowness of the "slow" CF card will not be as noticeable on reads as with writes.

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... imagine I'm making this argument without referencing cartoons.

thestinger

Package Maintainer (PM)

From: Toronto, Canada

Registered: 2010-01-23

Posts: 478

Re: Directories with high IO

/dev, /proc and /sys should be on the faster one too, right? I mean, they're dynamic and (partly) automatically populated, after all…

/proc is a virtual filesystem and /dev is in tmpfs (ram)

/sys is the same as /proc afaik

/tmp is used for things like compiling and /var has all the various databases and caches so those should be on the faster device for sure

/usr would mostly affect application load time (binaries/libraries/etc.) so I don't think it's a big deal b/c it won't actually do much to performance (/usr is pretty much read only when you aren't doing system maintenance)

I think the big choice you'll have to make is between having /home or /usr on the faster device (since those would be the two biggest dirs)

you could put the browser cache, etc in /tmp if /home is on the slow drive

CONCLUSION:

/ on the fast drive
/var on the fast drive
/tmp on the fast drive

choice between /usr or /home on the fast drive

Last edited by thestinger (2010-04-08 21:41:12)