[Beowulf] RE: SATA or SCSI drives - Multiple Read/write speeds.

Lombard, David N david.n.lombard at intel.com
Tue Dec 9 13:22:43 EST 2003


From: Robin Laing; Sent: Tuesday, December 09, 2003 8:23 AM
> Mark Hahn wrote:
> > nah.  it's basically just a design mistake to put two active PATA
disks
> > on the same channel.  it's fine if one is usually idle (say, cdrom
or
> > perhaps a disk containing old archives).  most people just avoid
putting
> > two disks on a channel at all, since channels are almost free, and
you
> > get to ignore jumpers.
> >
> So it would be a good idea to put data and /tmp on a different channel
> than swap?

This is true of *every* system, regardless of disk technology.

However, it's even better, if possible, to put enough memory in the box
to avoid swap.

> I agree but I am not looking at swap thrashing in the sense of many
> small files.  I am looking at 1 or 2 large files that are bigger than
> memeory while working.  I know on my present workstation I will work
> with a file that is 2X the memory and I find that the machine stutters
> (locks for a few seconds) every time there is any disk ascess.  I
> would like to add more ram but that is impossible as there are only
> two slots and they are full.  Management won't provide the funds.

What kernel are you using? There were a couple/few 2.4 kernels that
would behave badly with this.  Changing the kernel and/or tuning in
/proc can help, I ran in to this and used both fixes.  I don't have the
specifics with me, but they're googleable...

-- 
David N. Lombard

My comments represent my opinions, not those of Intel.
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