We are doing SEEK_SET fseek(fp,offset[i],SEEK_SET
We were running into this same issue on our san file system until we set the dma_cache_read_ahead to match our buffer size of 256k. Just wondering if there is away to set that within lustre. We are running 1.8 on the MDS and OSS and the clients running the fseek are are running 1.6 Thanks again. Rocky From: Andreas Dilger <andreas.dil...@oracle.com> To: Ronald K Long <rkl...@usgs.gov> Cc: lustre-discuss@lists.lustre.org Date: 04/09/2010 10:52 AM Subject: Re: [Lustre-discuss] fseeks on lustre On 2010-04-07, at 14:09, Ronald K Long wrote: > I am having an issue with our lustre file system. In our current > environment on a san file system opening a large file and doing > fseeks completes in under 2 seconds. Running that same routine on > our lustre file system the routine actually never finishes. Doing fseek() itself is only a client-side operation, so it should have no performance impact, UNLESS you are doing SEEK_END, which requires that the actual file size be computed on the client. That causes lock revocation from all of the clients and is an expensive operation. Using SEEK_CUR or SEEK_SET has no cost at all. > Are there any tunable parameter in lustre that can alleviate this > problem? It depends on what the problem really is. Cheers, Andreas -- Andreas Dilger Principal Engineer, Lustre Group Oracle Corporation Canada Inc.
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