<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 12 (filtered medium)">  <style>  </style>  </head> <body lang=EN-US link=blue vlink=purple> <div class=Section1> >Are you using tcp as transport?<o:p></o:p> <o:p> </o:p> I’ve tried both UDP and TCP and the same results on both. My understanding is that if you have only one switch between the devices, then UDP should be fine as long as there isn’t any packet loss. <o:p></o:p> <o:p> </o:p> From what I can tell, its not so much the transport of data between the client and server, just the commit time on the server. I think the steps are:<o:p></o:p> <o:p> </o:p> <![if !supportLists]>· <![endif]>NFS server receives data<o:p></o:p> <![if !supportLists]>· <![endif]>NFS server requests a commit of the data<o:p></o:p> <![if !supportLists]>· <![endif]>Data gets handed off to the file system<o:p></o:p> <![if !supportLists]>· <![endif]>File system writes the data<o:p></o:p> <![if !supportLists]>· <![endif]>A response is sent back to the NFS server that the commit was successful<o:p></o:p> <![if !supportLists]>· <![endif]>NFS server sends a response back to the client that it can send more data<o:p></o:p> <o:p> </o:p> I’m trying to get more detail on this process though and the above is just an educated guess. I even increased the amount of nfsd processes (the daemons) from 8 to the 32 with the exact same results. Changing the rsize and wsize didn’t do anything either. From my understanding, meta-data changes are small so increasing the size of the data chunks shouldn’t really make a difference. <o:p></o:p> <o:p> </o:p> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=2 width="100%" align=center> </div> From: redhat-sysadmin-list-bounces@redhat.com [mailto:redhat-sysadmin-list-bounces@redhat.com] On Behalf Of Chris Wornell Sent: Sunday, November 19, 2006 1:59 AM To: redhat-sysadmin-list@redhat.com Subject: NFS Help! Terrible performance with sync,fast performance with async<o:p></o:p> </div> <o:p> </o:p> I've got a problem that I've spent quite a bit of time on, though I'm not an expert at NFS. In summary, operations that require meta-data changes (such as file/directory creations/deletions), perform extremely slow over sync, but over 10x faster using async. I have two systems, connected to a GigE switch using intel pro 1000 NICs (jumbo frames is currently not enabled on any of the points). The NFS server is a dual-core opteron system with 1GB of RAM and 3x300 SAS disk RAID-5 on a Perc5/i controller with 256MB battery backed cache (write cache is enabled). The file system is ext3. I've configured nfsd to spawn 32 processes upon startup. I'm using defaults for export the nfs shares, no changes to rsize or wsize. The NFS client is a dual Xeon with 4GB of RAM and a single 7200rpm SATA disk. Both systems are running RHEL WS 3 Update 8 and kernel 2.4.21-47.0.1.ELsmp. For testing, I'm using bonnie++. The following are some sample test results that sum up the problem: Test on NFS server directly (not NFS loopback) -Sequential File Creation: 2976 -Sequential File Deletion: N/A -Random File Creation: 3077 -Random File Deletion: 9922 NFS test with sync enabled -Sequential File Creation: 39 -Sequential File Deletion: 79 -Random File Creation: 39 -Random File Delection: 65 NFS test with async enabled -Sequential File Creation: 575 -Sequential File Deletion: 1718 -Random File Creation: 543 -Random File Deletion: 1228 Based on the local performance of the NFS server, it does not appear the IO setup is the culprit. My understanding of the sync operation is a commit happens which means the NFS server doesn't reply back until the change has actually been committed to stable storage. There is something happening behind the scenes though which is causing a huge delay before the NFS server replies back the commit was complete. This question is actually work related and I'm planning to put the NFS server into production, but I'd rather not use async, even with a UPS and dual PSU's on the server. With the newer nfs-utils, sync is the default option as well so it seems like sync should perform relatively well. Another question is I don't quite understand how the data corruption happens if a power loss occurs on an NFS server using async. Even with sync, data transferred over the wire maybe loss if the nfs server gets shut down before that data is committed. Can anyone go into more detail on how the data corruption happens? Thanks a bunch!<o:p></o:p> <o:p> </o:p> Thanks, Chris Wornell Network Administrator, Information Technology Peerless Systems Corporation <a href="http://www.peerless.com/" title="http://www.peerless.com/">http://www.peerless.com</a> office: 310.727.5723 fax: 310.727.5715 <a href="mailto:cwornell@peerless.com" title="mailto:cwornell@peerless.com">mailto:cwornell@peerless.com</a> <o:p></o:p> <o:p> </o:p> </div> </body> </html>