[Beowulf] Parallel memory

Kimmo Kallio kallio at ebi.ac.uk
Thu Oct 20 06:20:21 EDT 2005


On Wed, 19 Oct 2005, Bogdan Costescu wrote:

> On Tue, 18 Oct 2005, Robert G. Brown wrote:
>
>> There was once also an online list discussion about swapping to an NFS 
>> mounted remote exported ramdisk
>
> There are some problems with this approach, which is in principle very 
> similar with swapping over NBD or iSCSI. A discussion about iSCSI just 
> happened 1-2 months ago on the netdev and linux-kernel mailing lists; the 
> main problem is what to do in case the memory becomes tight: a part of memory 
> has to be sent to the block device, but sending it requires allocating more 
> memory for the network transfer; sometimes some part of memory is sent out 
> just so that another part is copied back in, in which case more memory is 
> needed for the network transfer (for the reception) - both these situations 
> can result in a deadlock.
> So, swapping over network is not (yet) that reliable - doing this at the 
> application level, therefore knowing more-or-less the pattern of transfers, 
> seems much wiser.

This has been an interesting thread. Has anybody had a look at ATA Over 
ethernet (another alternative is HyperSCSI), as running directly over 
ethernet might just work ? A link for AOE utulities can be found in 
http://sourceforge.net/projects/aoetools . I've been looking 
semi-seriously into diskless setups and the lack of networkable swap is a 
showstopper for us.

Also for infiniband there is a study at
http://nowlab.cse.ohio-state.edu/publications/conf-papers/2005/liang-cluster05.pdf

Regards,

Mr Kimmo Kallio
System Administrator
European Bioinformatics Institute
Genome Campus
Hinxton
Cambridge
CB10 1SD
U.K.
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