Re: web write-up

[Shaun Dwyer]

Mike Meyer wrote:

In <[EMAIL PROTECTED]>, JacobRhoden <[EMAIL PROTECTED]> typed:

On Thursday 09 January 2003 12:09, Shaun Dwyer wrote:

is they probably didn't make seperate slices for /, /var and /usr.

What difference does it make as to wether these partions are seperate. I realise if you have more than one ide drive then having them on seperate drives is alot better. On single drive machines I usually make only one partion, what reasons are there to slice it?

[SWAG follows]

From a performance standpoint, putting them on separate slices on the

same disk is probably a loss. It forces the blocks in those file
systems to live spread out across the disk, meaning the time
optimizations are constrained to those blocks, whereas if you put them
all in one file system then the disk scheduler can play with the
entire disk.

That said *THIS DOESN'T MAKE ANY PRACTICAL DIFFERENCE*. The scheduler
already slices partitions up into cylinder groups and tries to make
files live on specific cylinder groups. Having different file systems
just means lets it pick from a smaller set of cylinder groups. If
your disk is so heavily loaded that this makes a difference, you
really want multiple spindles.

There are administrative reasons to split them up. For instance, the
backup for /usr is the FreeBSD CDROM set. / and /var I create backups
for, so /usr gets it's own file system, and /var lives on /. On a
second system, / and /usr are mounted read-only - well, they should be
- but /var has the web site on it, which gets updated at regular
intervals. So /var gets it's own file system, and /usr lives on /.

On my test system, which gets config files stored in perforce, I just
make everything one big file system.

	<mike

I Disagree.. it will make a difference. If you partion /var near the beginning of the disk (the fastest part - outer tracks) it will force
all the stuff in /var (being logs and stuff) to live at the faster area of the disk. If your server is being hit really hard, im sure you dont want it seeking all over the disk to write to logs. This could potentially add up to quite a performance hit. While an attempt is made to ensure that a file exists in the same cyl group, there is no garantee. if your logs grow to be quite large. im sure there are several other reasons to make seperate partitions. Off the top of my head: stop file systems from filling up if you have a process dumping large ammounts of data some where, if one file system is corrupted, you dont lose _everything_. Discounting the potential pefformance benefits, these two reasons alone should be enough to create seperate file systems.

--Shaun


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