[LUAU] Running a standard distro without swap space

Charles Lockhart lockhart at IfA.Hawaii.Edu
Sat May 14 00:17:50 PDT 2005


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



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