On Thu, Jan 6, 2011 at 3:02 PM, folkert <[email protected]> wrote: > nbd-client -h tells me: > Allowed values for blocksize are 512,1024,2048,4096
device blocksize can't be larger than page size > Now conventional jumbo frames (which become popular on Gb networks) are > 9000 bytes. So 1 8192 NBD block would fit in it nicely. The device's blocksize doesn't necessarily correspond to the size of the packets on the network. Because the scheduler can coalesce multiple I/Os, you usually end up with larger I/O requests when doing sequential reads/writes. When doing non-sequential I/O, you're going to end up with requests the size of the filesystem blocksize (4k generally). TCP is then going to break the larger requests into segments for optimal transfer given the physical layer's MTU, so the breakdown into proper sized network packets should be happening already. And changing the device's blocksize won't actually improve the non-optimal small I/O request case. In fact, it can be detrimental, as if the device's blocksize is larger than the filesystem blocksize then you'll end up doing read/modify/write instead of just write on smaller writes. -- Paul ------------------------------------------------------------------------------ Learn how Oracle Real Application Clusters (RAC) One Node allows customers to consolidate database storage, standardize their database environment, and, should the need arise, upgrade to a full multi-node Oracle RAC database without downtime or disruption http://p.sf.net/sfu/oracle-sfdevnl _______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
