[Beowulf] Should I go for diskless or not?

John Hearns hearnsj at googlemail.com
Fri May 15 10:30:24 EDT 2009

2009/5/15 Joe Landman <landman at scalableinformatics.com>:
>>>  Swap is an issue.  A somewhat hard to solve issue ... we'd recommend
> actually turning off swap (and swappiness in the kernel) for diskless.  Or
> put a USB drive in each machine and swap on that, though, honestly, that is
> as reliable as swapping over the network. E.g. don't do it.

At the risk of boring everyone here rigid with the "SGI" word, ICE
clusters mount swap via iSCSI.
It seems to work - I say seems, as I've never actually looked at a
blade doing swap in anger.
Which reminds me - I have a to-do list task which is to test the OOM
killer on one of these blades.
Guess I can look at it swapping at the same time as I stress it for OOM.

Two rules of thumb for swap though:

a) provision enough RAM on ya nodes for ya code

b) hire Samuel L Jackson to get medieval on the ass of any users dumb
enough to run code which leaks memory

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