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Re: [Linux-cluster] architecture discussion -- NFS clustering with iSCSI



Rainer Duffner wrote:

Am 28.01.2008 um 02:36 schrieb Terry:



Good questions:
1) Do you have concurrent writes to the same file from different nodes?
  1a) No


Well, that's one of the things GFS is good at ;-)


2) How many nodes do you have?
  2a) 3 to start, probably won't go beyond 12

OK, that's still in the range GFS can handle (AFAIK).

With an order of magnitude room for growth left.

I appreciate alternative ideas to NFS.  NFS could possibly introduce
performance issues (comments here appreciated).


One problem might be that NFS was never supposed to run on  GBit-networks.
Thus there is overhead.
But, OTOH, the vendors I mentioned have managed to squeeze a lot of performance out of NFS.
It's also a question of optimizing/matching NFS clients and servers.

I've found that NFS v3 over UDP with large rsize,wsize and jumbo frames works pretty well.

  The majority of the
system is write.  I would say 80%.


Do you have a lot of small files?
Small files are usually what degrades GFS-performance.

I don't think small files are what kills it, it's lots of files that slow things down.

Gordan


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