[zfs-discuss] Re: Moderate write speeds on Ubuntu
Niels de Carpentier
zfs at decarpentier.com
Thu Sep 19 08:25:25 EDT 2013
> On 18/09/13 20:31, bgribble at gmail.com wrote:
>> I'm also experiencing slow write behavior on ubuntu 12.04 with ZoL
>> 0.6.2. Running an 11x4TB drive raidz3 (ashift=12) connected to 2x M1015
>> flashed to IT mode with less than 6TB used i'm seeing this (xeon e5530,
>> 8GB ram, no dedup) :
>> time dd if=/dev/zero of=zerofile12.tst bs=4k count=4700000
>> 4700000+0 records in
>> 4700000+0 records out
>> 19251200000 bytes (19 GB) copied, 63.74 s, 302 MB/s
> ZFS raidz* write speed on any given vdev is limited to about the maximum
> write speed of a single drive.
> Unless you have 15,000 rpm drives, what you're seeing is about what I'd
No, sequential write speed scales pretty well with the number of drives,
IOPS don't. But in this case the 4k block size is likely the limiting
factor, using a larger block size should give much better results.
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