from reboot: zoizoi@shankara:~$ sudo blockdev --getra /dev/md0 [sudo] password for zoizoi: 256 zoizoi@shankara:~$ sudo blockdev --setra 2048 /dev/md0 zoizoi@shankara:~$ sudo dd if=/dev/md0 of=/dev/null bs=1M count=4000 4000+0 records in 4000+0 records out 4194304000 bytes (4.2 GB) copied, 7.53149 s, 557 MB/s zoizoi@shankara:~$ sudo dd if=/dev/md0 of=/dev/null bs=1M count=4000 4000+0 records in 4000+0 records out 4194304000 bytes (4.2 GB) copied, 0.600264 s, 7.0 GB/s zoizoi@shankara:~$ Liam On Thu, May 5, 2011 at 9:39 AM, Liam Kurmos <quantum.leaf@xxxxxxxxx> wrote: > On Thu, May 5, 2011 at 9:06 AM, Nikolay Kichukov <hijacker@xxxxxxxxx> wrote: >> -----BE >> It seems like he is reading directly from the raid device and not through the filesystem. So there are no filesystem >> caches in this way. > > phew! ... i think (see below) > > > I installed ubuntu 11.04 on the new system last night. > this morning i went to reconnect the old system drive (id disconnected > it for safety) and 'pop' a small piece of metal must have touched the > back of the loose drive and fried the board! ... oh joy. > > --luckily its an old drive and i have an identical spare so im hoping > i can swap the board and save all my work since last git commit. > > anyway.. this look different in 11.04. mdadm 3.1.4 > > /dev/md0: > Timing buffered disk reads: 594 MB in 3.00 seconds = 197.79 MB/sec > zoizoi@shankara:~$ sudo dd if=/dev/md0 of=/dev/null bs=1M count=1000 > 1000+0 records in > 1000+0 records out > 1048576000 bytes (1.0 GB) copied, 5.84755 s, 179 MB/s > zoizoi@shankara:~$ sudo dd if=/dev/md0 of=/dev/null bs=1M count=1000 > 1000+0 records in > 1000+0 records out > 1048576000 bytes (1.0 GB) copied, 0.152353 s, 6.9 GB/s > > even though im accessing the block device directly it does look like > im getting buffering in natty! I don't think i was in 10.10 and > certainly wasnt getting 7GB/s > > raid10 f2 performance is right down vs what i got last night (i got > 470MB/s first try after creating the array so dont think there was > buffering. > > my md1 raid5 was also slow again. readahead on both defaulted down to > 256 on 11.04 > > I applied Neil's x8 fix to both md0 and md1 and now the dd test look > much better. > > sudo dd if=/dev/md0 of=/dev/null bs=1M count=4000 > 4000+0 records in > 4000+0 records out > 4194304000 bytes (4.2 GB) copied, 7.62018 s, 550 MB/s > > a little too good! > i could see in the system monitor that i didnt have the large 4G > buffer (i do post this test). Something i did must have reset the > buffer. I could see a small amount of buffer in system monitor so > maybe it was 1GB. I appreciate these are not the best test but not > that hdparm is much worse. Once i set the 2048 sector readahead i gets > totally unrealistic. > > zoizoi@shankara:~$ sudo blockdev --setra 2048 /dev/md0 > zoizoi@shankara:~$ sudo hdparm -t /dev/md0 > > /dev/md0: > Timing buffered disk reads: 5294 MB in 3.00 seconds = 1762.34 MB/sec > zoizoi@shankara:~$ sudo blockdev --setra 256 /dev/md0 > zoizoi@shankara:~$ sudo hdparm -t /dev/md0 > > /dev/md0: > Timing buffered disk reads: 582 MB in 3.00 seconds = 193.78 MB/sec > > anyway, it looks like i'm getting good read speed now with 2048 > lookahead, ill do another dd test on reboot. > > > thanks to you all for the helpful responses, > > Liam > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
