Brian Chee wrote:
Actually I have a question...why would you want to run a machine without
swap? There are good reasons if you're running an embedded linux machine,
but for normal machines I've seen folks setup unix boxes that boot from the
network but ONLY do swap to the local hard disk. Those old xterms did this
alot just so that you don't swap over the network.
We're not using our machines as general desktop platforms. They're part
of a system. In the current case I'm looking at, the computer is
receiving data via a fiber link on one pci bus, processing that data,
and then writing the data to disk across a second pci bus while we're
still reading in more data over the first pci bus. We've (hopefully)
managed to handle the contention issues internal to the program, but we
found that the system loses balance and starts dropping data
(irreplacable data) somewhat randomly if physical memory fills up and
the mm starts using the swap partition. Basically the primary
application will be working fine, then we'll start up something other
stuff (slickedit, firefox, tkcvs, etc.), and at some point the swap
partition starts getting used and the primary application performance
starts being randomly flaky. This would be fine if we had some big
shiny flag that would shoot up and alert the user that the system needs
to be re-balanced. But we don't.
One way that we could possibly fix this is to just disable the swap
partition. I'd been hoping that new applications that would exceed the
physical memory on process load would just fail, flagging to the user
that they're misbehaving, but instead the machine just slows down a
lot. This is slightly more problematic for how we use the system.
I've also talked to other people that were designing instrumentation for
astronomy, and there interest in getting rid of the drives was based on
what I'm told is a high rate of disk failure at altitude. If the
primary source of failure is the disk, then why have it? But, please
somebody correct me if I'm wrong, no disk no swap space?
-Charles
