On Mon, 22 Sep 2008 10:21:32 -0600 "Chris Worley" <worleys@xxxxxxxxx> wrote: > On Fri, Sep 19, 2008 at 7:40 PM, Chris Worley <worleys@xxxxxxxxx> wrote: > > > > I'm running CentOS 5.2 targets w/ a 2.6.24 kernel. The initiator is > > Win2003. On the initiator side, the fs is formated NTFS w/ a 4K block > > size (and the NTFS block size seems to have nothing to do w/ this > > issue). > > > > Watching iostat on the target side, everything is being written to the > > underlying disk in 512 byte operations. > > > > Best I can tell, it's the Linux side that's fragmenting the I/O. > > > > I could get a lot better performance if these were coalesced into > > larger, variable, block sizes (i.e. what's being written from the > > initiator side is much larger blocks). > > > > Is there something tgtd queries on the disk to get this information? tgtd doesn't do anything special. It opens a file on your file system (or a device file such as /dev/sda) and performs read/write system calls. > > I don't see an fstat64 use of st_blksize in the source. > > > > I can put a dummy md "linear" device atop the disk and set the MD > > device's chunk size to 4K... then everything to the MD device (as well > > as to the underlying disk) is passed in 4K blocks... which performs > > much better (except even larger blocks would get better performance if > > the user is writing larger blocks... and smaller blocks do a > > read-modify-write that causes 3x the IO activity to perform). > > I changed the MD to chunk at 8K blocks (and the NTFS on the w2003 > side to use 8k blocks), and the tgtd was still chunking at 4K blocks. > > Does anybody have an idea where the fragmenting is occurring and/or > how to stop it? Not sure, but I think that the problem looks more generic one, not specific to tgtd, right? -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
