Am Montag, 7. Mai 2012 schrieb Daniel Pocock: > I've been having some NFS performance issues, and have been > experimenting with the server filesystem (ext4) to see if that is a > factor. Which NFS version is this? > The setup is like this: > > (Debian 6, kernel 2.6.39) > 2x SATA drive (NCQ, 32MB cache, no hardware RAID) > md RAID1 > LVM > ext4 > > a) If I use data=ordered,barrier=1 and `hdparm -W 1' on the drive, I > observe write performance over NFS of 1MB/sec (unpacking a big source > tarball) Is this a realistic workload scenario for production use? > b) If I use data=writeback,barrier=0 and `hdparm -W 1' on the drive, I > observe write performance over NFS of 10MB/sec > > c) If I just use the async option on NFS, I observe up to 30MB/sec > > I believe (b) and (c) are not considered safe against filesystem > corruption, so I can't use them in practice. Partly. b) can harm filesystem consistency unless you disable write cache on the disks c) won´t harm local filesystem consistency, but should the nfs server break down all data that the NFS clients sent to the server for writing which is not written yet is gone. > - or must I just use option (b) but make it safer with battery-backed > write cache? If you want performance and safety that is the best option from the ones you mentioned, if the workload is really I/O bound on the local filesystem. Of course you can try the usual tricks like noatime, remove rsize and wsize options on the NFS client if they have a new enough kernel (they autotune to much higher than the often recommended 8192 or 32768 bytes, look at /proc/mounts), put ext4 journal onto an extra disk to reduce head seeks, check whether enough NFS server threads are running, try a different filesystem and so on. -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
