On Thu, Mar 05, 2009 at 10:18:55AM -0700, Igor Sola wrote: > Apologies in advance if this email is inappropriate for this mailing > list. If so please let me know of a more suitable one. > > I noticed a significant performance difference when comparing a > Centos5 (kernel 2.6.18) or Ubuntu (2.6.27-11) with a RH8 (kernel 2.4). > All use NFS v3. > The RH8 nfsd is faster than the 2.6 one even though it runs in an > older, lower spec machine. > > See test details below > > Centos 5 x86_64 kernel 2.6.18-92.1.22.el5 > > RH8 2.4.20-30.8.multi_lun.smp #1 SMP i386 GNU/Linux > > 1Gb connection between machines > > File sizes are 1GB. The read speed of these files in the local machine > filesystem (server) is around 98MBs in the Centos5 machine and around > 65MBs in the old RH8 machine. > > .- First of all I wanted to measure how the network alone performs > while using NFS. > So in the server side I run a "cat" command on the 1GB file to > /dev/null. At this point the file system has the 1GB file cached in > memory. In the client side a "cat" on the same file gives me a speed > of about 113MBs. Which is consistent with the 1Gb network. There is no > performance hit. So far so good. > > > .- The second test is reading from disk an uncache (in server and > client) file. In the server and client I made sure I flushed the 1GB > file from the memory. Between Centos5 machines the performance was > about 35MBs (64% drop from the 98MBs disk read). Between RH8 machines > the performance was 55MBs (15% drop from the 65MBs) > > This second test was repeated for ext2, ext3, xfs with no significant > differences. > > Please note that the %iowait more than doubles when reading the file > from the NFS partition vs the file system partition in the 2.6 kernels > > .- I run a third test just to make sure the problem is somehow related > to the nfs daemon. I mounted the nfs partition local to the nfs server > so the network was out the equation. I got the same poor results, no > difference. > > Any ideas are most welcome, What version of nfs are you using, over what transport (tcp or udp)? What are the export options? I wonder if something's going wrong with readahead. --b. -- 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
