suggestions for optimal filesystem-layout over multiple harddrives?

[Kent Stewart]

On Sunday 06 June 2004 10:10 pm, Chuck Swiger wrote:
> Geert Hendrickx wrote:
> > using multiple harddisks can increase performance, since I/O can be
> > done in parallel.  But what would be an optimal filesystem-layout
> > on, say, two disks of equal size?  Swap should evidently be spread
> > equally over the different drives.  As for the filesystems, say I'd
> > have a large /usr and /home, each on one harddrive, and smaller /,
> > /var and /tmp which could reside on either disk.  / and /usr would
> > be mostly read-only.
>
> There is nothing wrong with the approach you are taking, and it will
> indeed help balance load out between multiple spindles.  That being
> said, you have to know (by measuring) or at least predict what your
> I/O access patterns are between the various filesystems in order to
> gain full advantage.
>
> An easier way of balancing load between two or more drives involves
> using RAID-0 striping, although the drives do not have to be equal in
> size. Commodity ATA RAID controllers like Highpoint, Promise, & 3ware
> are fairly cheap, or one could use software RAID like vinum.

I was worried about buildworld speed and found I could optimize for that 
very easy. You need 3 HDs on their own controller and create mount 
points for /usr/src and /usr/obj on the 2nd and 3rd controller. Since 
the HDs are so large, I also created a mount point for /usr/ports on 
one of those other controllers. You only see 10-15% faster build times 
when you do this and it is a question of how long you are going to run 
your system before you are paid back for the time you spent worrying 
about it.

From my days of benchmarking supercomputers, we found it was always easy 
to move files produced by users onto a different set of HDs than the 
system was using. You separated the files the system wanted quick 
access to from the files being produced by users. The programs we ran 
generated a lot of data and disk caching was much more important than 
location of the files. What becomes important with caching is whether 
fast access to files you want to read is most important or data 
integrity. If data integrity is not important because you are going to 
restart the program and run it from scratch, then write behind caching 
is easy to setup. 

I haven't encountered any environment like that since I retired. 
My /home/user accounts are all on /usr.

Kent

-- 
Kent Stewart
Richland, WA

http://users.owt.com/kstewart/index.html