Re: disk partition schemes
On Saturday 23 June 2001 04:10, Nick Jennings wrote:
> > > one and waste space. Do the performance gains outweigh this? (I'm
> > > not terribly worried about the redundancy with the RAID 10 and
> > > all).
> >
> > What performance gains are you referring to?
>
> The main performance benefit to having directories reside on their own
> partition relates to file write/read access. It's very important to
> have var on it's own seperate partition, specifically because it's
> probably the most actively written to directory.
OK. If you have a single physical hard drive or RAID array, the how will
having /var on a separate partition give any benefit? Disk access still
goes to the same hardware and is still limited by head seek times and
rotational delays of the hardware. Having two seeks on the same
partition or two seeks on separate partitions should not perform any
differently.
However if you have a single large partition then when you are writing
data the FS drivers can optimise things.
> Another little performance gain is the order in which you partition
> your disks (the closer to the 0'th cylinder the faster the access time.
This depends on the type of device. This is a general rule that doesn't
always apply. But when it does apply it's not so small. 50% extra
performance at the start of the disk is not uncommon.
AFAIK I'm the only person to publish a benchmark program to measure
this...
> For instance, this is the order in which I usually go about
> partitioning my drive (note: it varies depending on it i'm setting up a
> workstation or a server, but they are similar).
>
> <swap> size: totalmem*2 (64mb = 128mb partition)
> /
> /tmp
> <extended>
> /usr
> /var
> /home
Swap is often the most used partition. Root is probably the least. /tmp
and /home are both candidates for the most used partition. Having things
separate like this means that in many common usage situations you'll have
the heads seeking across the entire disk all the time. Having a single
partition could increase performance...
> If I run out of room on /var/www or /var/cvs or something, I can stick
> another disk in and mount that in its place instead. I used to get
> worried about wasted space, but if you just over estimate a bit, you
> should be fine with most of the partitions that don't grow (like /,
> /tmp, /usr). And you just give the most space the the ones that can
> grow. Now I find a nice partitioning scheme to be much more manageable
> and the performance is very noticable.
If sticking another disk in is so easy then why not just install lots of
disks in a RAID array from the start? That'll get the best performance...
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