What is the distribution of NFS read/write sizes?
SFS2008 provides more flexibility for NFS I/O sizes and over-the-wire transfer sizes. SFS97 always used an 8 KB transfer size, and counted physical READ or WRITE operations. SFS2008 automatically negotiates the NFSv3 server’s maximum supported transfer size, up to 32 KB. To equalize op counts between servers that support different transfer sizes, SFS2008 counts logical READ and WRITE operations, not physical transfers. If the selected logical READ or WRITE size is larger than the server’s maximum supported transfer size, SFS2008 breaks up the logical operation into several physical operations. The server only gets credit for performing one logical READ or WRITE, regardless of how many physical transfers are necessary to move the data. Since SFS2008 uses a different set of access size buckets than SFS97, it is not possible to directly compare the I/O size distributions between SFS97 and SFS2008. The following tables describe the SFS2008 and SFS97 I/O size distributions.
