Re: 256MB RAM systems can need 1GB swap... Re: Partitioning....
On Thu, 13 Aug 1998, Christopher Barry wrote:
>
> Anyone care to explain why huge swap spaces should be spread across
> multiple disks? I can understand the need for multiple partitions, as
> swap partitions bigger than 128MB IIRC won't be able to use more than
> 128MB of it, but why should the multiple partitions be spread across
> multiple disks? Does doing this automatically make them RAID like so
> that writes and reads for the swap space are distributed so that each
> additional disk you distribute swap across increases your overall swap
> speed as is true with some RAID levels?
1. It is not true (any more...) that the kernel doesn't use more then
128MB, it can use up to 4GB in one partition.
2. Putting the swap in several different disks does make the access time
faster, but this is not the issue of RAID. RAIDs are good for their
ability to continue working even though one of the disks is not working
anymore (the RAID3 keeps an extra disk for parity bits, while the RAID5
does it on the "regular" disks.)
>
> If this is true, then in the name of the eaking out every last bit of
> swap performance that I'll never use I may just hook up an old unused
> 2GB SCSI disk I have (well, unused until I have enough other 'unused'
> parts to build a new computer to use it) and distribute my swap across
> it and my current disk (and mind as well make a few extra ext2
> partitions on it while it's sitting on the SCSI chain so it sees more
> use). Certainly couldn't hurt, but might give me a 1% performance boost
> .0001% of the time I'm using my computer. :)
You can do that, just remember that if you r computer has enough physical
memory, and you don't use a lot of "heavy" processes (Netscape + a mail
reader is not enough), the swap space will not be used, and if your system
will have to use 2GB worth of swap space it will crash because of the
thrashing...
>
> Steve Lamb wrote:
> >
> > On Wed, 12 Aug 1998 15:31:14 -0400 (EDT), Will Lowe wrote:
> >
> > >Well, give yourself at least twice as much swap space as physical memory
> > >(for 64 megs of ram, go for 128 megs of swap). Swap should be a seperate
> > >partition.
> >
This is not true, you can use swap files, and not swap partitions.
Liran.
---
http://www.math.tau.ac.il/~liranz/
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