On Tue, 2007-08-14 at 20:36 +0200, Bastian Blank wrote: > On Tue, Jun 19, 2007 at 07:18:38PM +0200, Bastian Blank wrote: > > But it is slow. I can write at most 15MiB/s to the disks, regardless of > > the count of the initiators and disks. > > I did another round of tests with 2.6.22 and a corresponsing patchset > and an uptodate tgtd with disabled controller lun (it breaks my setup > which needs the boot disk on lun 0). > > Writing on an exported device shows weird behaviour. iostat shows many > write _and_ read requests, even if the initiator only emits write > requests: what kind of write io u did? make a fs and run bonnie? try simple dd on a raw device (no fs) and see the performance. if write result is much better and u do not see read in iostat, u meet an align issue simply like what we had in IET list. > > | Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util > | sdb 3733.90 4177.60 525.80 72.70 34138.40 34002.40 113.85 19.94 33.32 1.38 82.76 > > If the initiator emits read requests, it is okay: > > | Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util > | sdb 13798.50 0.40 1955.31 0.20 126057.72 4.81 64.47 1.18 0.60 0.43 83.21 > > There is only lvm between it. This looks like some sort of read-ahead > for the data, which should not happen for write requests. I tried to dig > a little bit in the block code but was not able to found the cause. > > Bonnie shows the following: > | Version 1.03 ------Sequential Output------ --Sequential Input- --Random- > | -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- > | Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP > | test.track.rz.un 2G 21914 10 15207 4 59795 6 305.8 0 > > Bastian > -- Ming Zhang @#$%^ purging memory... (*!% http://blackmagic02881.wordpress.com/ http://www.linkedin.com/in/blackmagic02881 -------------------------------------------- |