On Mon, May 07, 2012 at 01:59:42PM +0000, Daniel Pocock wrote: > > > On 07/05/12 09:19, Daniel Pocock wrote: > > > >>> Ok, so the combination of: > >>> > >>> - enable writeback with hdparm > >>> - use ext4 (and not ext3) > >>> - barrier=1 and data=writeback? or data=? > >>> > >>> - is there a particular kernel version (on either client or server side) > >>> that will offer more stability using this combination of features? > >> > >> Not that I'm aware of. As long as you have a kernel > 2.6.29, then LVM > >> should work correctly. The main problem is that some SATA hardware tends > >> to be buggy, defeating the methods used by the barrier code to ensure > >> data is truly on disk. I believe that XFS will therefore actually test > >> the hardware when you mount with write caching and barriers, and should > >> report if the test fails in the syslogs. > >> See http://xfs.org/index.php/XFS_FAQ#Write_barrier_support. > >> > >>> I think there are some other variations of my workflow that I can > >>> attempt too, e.g. I've contemplated compiling C++ code onto a RAM disk > >>> because I don't need to keep the hundreds of object files. > >> > >> You might also consider using something like ccache and set the > >> CCACHE_DIR to a local disk if you have one. > >> > > > > > > Thanks for the feedback about these options, I am going to look at these > > strategies more closely > > > > > I decided to try and take md and LVM out of the picture, I tried two > variations: > > a) the boot partitions are not mirrored, so I reformatted one of them as > ext4, > - enabled write-cache for the whole of sdb, > - mounted ext4, barrier=1,data=ordered > - and exported this volume over NFS > > unpacking a large source tarball on this volume, iostat reports write > speeds that are even slower, barely 300kBytes/sec How many file creates per second? --b. > > b) I took an external USB HDD, > - created two 20GB partitions sdc1 and sdc2 > - formatted sdc1 as btrfs > - formatted sdc2 as ext4 > - mounted sdc2 the same as sdb1 in test (a), > ext4, barrier=1,data=ordered > - exported both volumes over NFS > > unpacking a large source tarball on these two volumes, iostat reports > write speeds that are around 5MB/sec - much faster than the original > problem I was having > > Bottom line, this leaves me with the impression that either > - the server's SATA controller or disks need a firmware upgrade, > - or there is some issue with the kernel barriers and/or cache flushing > on this specific SATA hardware. > > I think it is fair to say that the NFS client is not at fault, however, > I can imagine many people would be tempted to just use `async' when > faced with a problem like this, given that async makes everything just > run fast. > > -- > 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 -- 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
