Messages in this thread | | | Date | Wed, 22 Jan 2003 16:32:08 +0100 | Subject | Re: NFS client problem and IO blocksize | From | Trond Myklebust <> |
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>>>>> " " == Oliver Tennert <tennert@science-computing.de> writes:
> OK thanks. But I am sorry to push you once more, Trond: can you > now give me just a brief explanation of difference between the > "wsize" option and the "wtmult" attribute? Is it better now to > disable O_DIRECT and use a larger wsize/rsize, or to enable it > and be content with the parameters it uses?
wsize gives you the maximum number of bytes NFS is allowed to send in a single NFSPROC_WRITE RPC call. (rsize gives the same number for NFSPROC_READ calls). The NFS client will usually wait until it has 'wsize' bytes or more in the page cache before it tries to send anything over to the server.
OTOH wtmult has nothing to do with RPC, and has more to do with the disk organization on the server. As I understand it, in many cases the significance of this value lies in the fact that hardware operations to the disk have a lower limit on the number of bytes that can be read/written. IOW if your write is not aligned to a 'wtmult' boundary, then the server may be forced to read in the remaining data from the disk before it writes the entire block back.
Cheers, Trond - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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