On Sun, Feb 28, 2010 at 4:45 AM, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote: > > > On Sat, 27 Feb 2010, Bill Davidsen wrote: > >> Justin Piszcz wrote: >>> >>> >>> On Sun, 28 Feb 2010, Neil Brown wrote: >>> >>>> On Sat, 27 Feb 2010 08:47:48 -0500 (EST) >>>> Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote: >>>> >>>>> Hello, >>>>> >>>>> I have two separate systems and with ext4 I cannot get speeds greater >>>>> than >>>>> ~350MiB/s when using ext4 as the filesystem on top of a raid5 or raid0. >>>>> It appears to be a bug with ext4 (or its just that ext4 is slower for >>>>> this >>>>> test)? >>>>> >>>>> Each system runs 2.6.33 x86_64. >>>> >>>> Could be related to the recent implementation of IO barriers in md. >>>> Can you try mounting your filesystem with >>>> -o barrier=0 >>>> >>>> and see how that changes the result. >>>> >>>> NeilBrown >>> >>> Hi Neil, >>> >>> Thanks for the suggestion, it has been used here: >>> http://lkml.org/lkml/2010/2/27/66 >>> >>> Looks like an EXT4 issue as XFS does ~600MiB/s..? >>> >>> Its strange though, on a single hard disk, I get approximately the same >>> speed for XFS and EXT4, but when it comes to scaling across multiple disks, >>> in RAID-0 or RAID-5 (tested), there is a performance problem as it hits a >>> performance problem at ~350MiB/s. I tried multiple chunk sizes but >>> nothing >>> seemed to made a difference (whether 64KiB or 1024KiB), XFS performs at >>> 500-600MiB/s no matter what and EXT4 does not exceed ~350MiB/s. >>> >>> Is there anyone on any of the lists that gets > 350MiB/s on a mdadm/sw >>> raid >>> with EXT4? >>> >>> A single raw disk, no partitions: >>> p63:~# dd if=/dev/zero of=/dev/sdm bs=1M count=10240 >>> 10240+0 records in >>> 10240+0 records out >>> 10737418240 bytes (11 GB) copied, 92.4249 s, 116 MB/s >> >> I hate to say it, but I don't think this measures anything useful. When I >> was doing similar things I got great variabilty in my results until I >> learned about the fdatasync option so you measure the actual speed to the >> destination and not the disk cache. After that my results were far slower >> and reproducible. > > fdatasync: > http://lkml.indiana.edu/hypermail/linux/kernel/1002.3/01507.html How did you format the ext3 and ext4 filesystems? Did you use mkfs.ext[34] -E stride and stripe-width accordingly? AFAIK even older versions of mkfs.xfs will probe for this info but older mkfs.ext[34] won't (though new versions of mkfs.ext[34] will, using the Linux "topology" info). -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
