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Date: Sat, 27 Feb 2010 08:47:48 -0500 (EST) From: Justin Piszcz <jpiszcz@...idpixels.com> To: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org, linux-ext4@...r.kernel.org cc: Alan Piszcz <ap@...arrain.com> Subject: mdadm software raid + ext4, capped at ~350MiB/s limitation/bug? 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. 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-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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