Re: 256MB RAM systems can need 1GB swap... Re: Partitioning....
Christopher Barry wrote:
>
> The latest Debian install manual when addressing the need of how big you
> need to make your swap partition says:
>
> "That still leaves the question of swap space. There are as many views
> on how much swap you need as there are Unix administrators. One rule of
> thumb which works well is to use as much swap as you have RAM, although
> there probably isn't much point in going over 64MB of swap for most
> users. If you start using that much swap, you should get more RAM. Of
> course, there are exceptions. If you are trying to solve 10000
> simultaneous equations on a machine with 256MB of RAM you may need a
> gigabyte (or more) of swap. If your swap requirements are this high,
> however, you should probably try to spread the swap across different
> disks."
>
> So I suppose the "For workstations the more RAM you have, the less
> you'll need SWAP" isn't true for 100% of workstations, but I'll be
> damned if my 64MB Pentium-MMX has ever swapped much even with Netscape
> mail and bunch of browsers open and a kernel compile running in the
> background.
>
Wow are you lucky, for some reason when I run netscape it sucks all of
my RAM and uses ~30Mb of swap (and all my 32Mb of RAM). I posted a
question about a month ago on this but those who helped me noticed some
of the same problems but not to the extent that I had.
> 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?
>
If you spread the swap partitons across multiple disks then SCSI can do
some 'multitasking' buy telling disks to read or write data while
waiting for another disk to finish it's operation.
> 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. :)
>
Yah, but it makes you feel good doesn't it?
> 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.
> >
> > Actually, this is antiquated advice to be handing out. On my Debian
> > system this is what free turns up:
> >
> > {morpheus@teleute:/home/morpheus}free
> > total used free shared buffers cached
> > Mem: 63332 61784 1548 27160 32000 16208
> > -/+ buffers/cache: 13576 49756
> > Swap: 14328 16 14312
> >
> > 14Mb of SWAP and 63Mb of RAM. For workstations the more RAM you have,
> > the less you'll need SWAP. The only time this machine has touched swap was
> > because of the Netscape memory leak. So why waste the HD space for something
> > that is never used?
Really? What version of netscape do you have, and more importantly is
it fixed in the newer versions?
> >
> > Also, the 2x RAM rule of thumb is based on, IIRC, BSD systems which map
> > RAM into the swap space so to get any swap you had to make the swap partition
> > as large as RAM and then some.
> >
> > So, for a workstation, the lower the RAM I'd say the larger the swap.
> > Something like:
> > RAM/SWAP
> > 4/32
> > 8/32
> > 16/24
> > 32/16
> > 64/16
> >
> > Servers, the rule of thumb is, what do you plan to run on the machine and
> > make sure your RAM/SWAP covers it.
> >
> > --
> > Steve C. Lamb | Opinions expressed by me are not my
> > http://www.calweb.com/~morpheus | employer's. They hired me for my
> > ICQ: 5107343 | skills and labor, not my opinions!
> > ---------------------------------------+-------------------------------------
> >
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>
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