lkml.org 
[lkml]   [2010]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: mdadm software raid + ext4, capped at ~350MiB/s limitation/bug?
    On Sat, 27 Feb 2010 08:47:48 -0500 (EST)
    Justin Piszcz <jpiszcz@lucidpixels.com> 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


    >
    > Can someone please confirm?
    >
    > Here is ext4:
    >
    > # dd if=/dev/zero of=bigfile bs=1M count=10240
    > 10240+0 records in
    > 10240+0 records out
    > 10737418240 bytes (11 GB) copied, 29.8556 s, 360 MB/s
    >
    > The result is the same regardless of the RAID type (RAID-5 or RAID-0)
    >
    > Note, this is not a bandwidth problem:
    >
    > # dd if=/dev/zero of=/dev/md0 bs=1M count=10240
    > 10240+0 records in
    > 10240+0 records out
    > 10737418240 bytes (11 GB) copied, 17.6871 s, 607 MB/s
    >
    > With XFS:
    >
    > p63:~# mkfs.xfs -f /dev/md0
    > p63:~# mount /dev/md0 /r1
    > p63:~# cd /r1
    > 10240+0 records in
    > 10240+0 records out
    > 10737418240 bytes (11 GB) copied, 17.6078 s, 610 MB/s
    >
    > NOTE: With a HW raid controller (OR using XFS), I can get > 500 MiB/s,
    > this problem only occurs with SW raid (Linux/mdadm).
    >
    > Example (3ware 9650SE-16PML RAID-6, 15 drives (using EXT4)
    > $ dd if=/dev/zero of=bigfile bs=1M count=10240
    > 10240+0 records in
    > 10240+0 records out
    > 10737418240 bytes (11 GB) copied, 21.1729 s, 507 MB/s
    >
    > Justin.
    > --
    > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html



    \
     
     \ /
      Last update: 2010-02-27 22:03    [W:0.042 / U:29.512 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site