Hi Robert, I have checked that the cache partition (/dev/sdc1) starts at 2048, it should be properly aligned. Similarly for the backing store partition (/dev/sdb1), it starts at 2048 at well. Thanks, Patrick >________________________________ > From: Robert Frånlund <robert.franlund@xxxxxxxxxxxx> >To: Patrick Ng <ppng@xxxxxxxxx> >Cc: "linux-bcache@xxxxxxxxxxxxxxx" <linux-bcache@xxxxxxxxxxxxxxx> >Sent: Friday, May 17, 2013 2:22 AM >Subject: Re: Poor performance with bcache write-back mode > > > >Hi, > > >Have you aligned your partitions on the SSD to at-least 4 KiB block-size, even better with 1 MiB? > > >Best regards, >Robert > > > > > > > >2013/5/16 Patrick Ng <ppng@xxxxxxxxx> > >Hi all, >> >>I have installed Linux kernel 3.9.2 in my Fedora 18. When I ran FIO in bcache write-through mode, the performance was good, but running a similar test in bcache write-back mode, I got very poor performance. >>Did I miss any options when setting the write-back mode? >> >>Environment >>=========== >>500G backing store at /dev/sdb1 >>150G SSD at /dev/sdc1 >> >>Write-through mode >>================== >>make-bcache -B /dev/sdb1 -C /dev/sdc1 >>echo /dev/sdb1 > /sys/fs/bcache/register >>echo /dev/sdc1 > /sys/fs/bcache/register >>mkfs.ext4 /dev/bcache0 >>mount /dev/bcache0 /mnt/bcache >> >> >>Running FIO with random, 100% read, iosize=4096, queue depth=16 >>the result is approx. 65k IOPS >> >> >>Write-backe mode (setup is almost the same as write-through except the extra step at the end "echo writeback ...") >>================ >>make-bcache -B /dev/sdb1 -C /dev/sdc1 >>echo /dev/sdb1 > /sys/fs/bcache/register >>echo /dev/sdc1 > /sys/fs/bcache/register >>mkfs.ext4 /dev/bcache0 >>mount /dev/bcache0 /mnt/bcache >>echo writeback > /sys/block/bcache0/bcache/cache_mode >> >>Running FIO with random, 100% read, iosize=4096, queue depth=16 >>the result is approx. 12k IOPS >> >>Running FIO with random, 80% read 20% write, iosize=4096, queue depth=16 >>the result is approx. 2k IOPS >> >>Thanks, >>Patrick >>-- >>To unsubscribe from this list: send the line "unsubscribe linux-bcache" 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-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
