[zfs-discuss] slow writes on EBS

Jake A. jake.angerman at 10gen.com
Fri Jan 10 18:31:30 EST 2014


If I toggle a given EBS device between the two file systems, I can 
reproduce the issue:

# zpool create tank /dev/xvdh
# cd /tank
# dd if=/dev/zero of=blah bs=1024k count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, *55.0079 s, 19.1 MB/s*
# cd /
# zfs umount tank
# zpool destroy tank
# mkfs.ext4 /dev/xvdh
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
3276800 inodes, 13107200 blocks
655360 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
400 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 
2654208,
        4096000, 7962624, 11239424

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
# mount /dev/xvdh /ext4
# cd /ext4
# dd if=/dev/zero of=blah bs=1024k count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, *0.873486 s, 1.2 GB/s*

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