On Jun. 19, 2008, 15:04 +0300, Peter Staubach <staubach@xxxxxxxxxx> wrote: > Krishna Kumar2 wrote: >>> 200 processes: >>> >> By "200 processes", I meant 200 dd's, each reading from /dev/zero and >> writing to a file on the filesystem. The script "nfs" was run twice, first >> with >> a local filesystem and the second time with the same filesystem NFS >> mounted. >> >> > > Well, you aren't exactly comparing apples to apples. The NFS > client does close-to-open semantics, meaning that it writes > all modified data to the server on close. The dd commands run > on the local file system do not. You might trying using > something which does an fsync before closing so that you are > making a closer comparison. try dd conv=fsync ... Benny > > All that said, yes, one would expect a slow down. How much is > debatable and varies from platform to platform and load to load. > > I would also advise care when running NFS like that. It is > subject to deadlock and is not recommended. > > ps > >> Thanks, >> >> - KK >> >> linux-nfs-owner@xxxxxxxxxxxxxxx wrote on 06/19/2008 12:16:23 PM: >> >> >>> Hi, >>> >>> I am running 2.6.25 kernel on a [4 way, 3.2 x86_64, 4GB] system. The test >>> is doing I/O on a local ext3 filesystem, and measuring the bandwidth, and >>> then NFS mounting the filesystem loopback on the same system. I have >>> configured 64 nfsd's to run. The test script is attached at the bottom. >>> >>> My configuration is: >>> /dev/some-local-disk : /local >>> NFS mount /local : /nfs >>> >>> The result is: >>> 200 processes: >>> /local: 108000 KB/s >>> /nfs: 66000 KB/s: Drop of 40% >>> >>> 300 processes (KB/s): >>> /local: 112000 KB/s >>> /nfs: 57000 KB/s: Drop of 50% >>> >>> I am not using any tuning, though I have tested with both >>> sunrpc.tcp_slot_table_entries=16 & 128 >>> >>> Is this big a drop expected for a loopback NFS mount? Any >>> feedback/suggestions are very >>> appreciated. >>> >>> Thanks, >>> >>> - KK >>> >>> (See attached file: nfs)[attachment "nfs" deleted by Krishna >>> >> Kumar2/India/IBM] >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Benny Halevy Software Architect Tel/Fax: +972-3-647-8340 Mobile: +972-54-802-8340 bhalevy@xxxxxxxxxxx Panasas, Inc. The Leader in Parallel Storage www.panasas.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
