On Tue, Jun 14 at 8:04, Paul Kraus wrote:
On Mon, Jun 13, 2011 at 6:01 PM, Erik Trimble <erik.trim...@oracle.com> wrote:
I'd have to re-look at the exact numbers, but, I'd generally say that
2x6raidz2 vdevs would be better than either 1x12raidz3 or 4x3raidz1 (or
3x4raidz1, for a home server not looking for super-critical protection (in
which case, you should be using mirrors with spares, not raidz*).
I saw some stats a year or more ago that indicated the MTDL for raidZ2
was better than for a 2-way mirror. In order of best to worst I
remember the rankings as:
raidZ3 (least likely to lose data)
3-way mirror
raidZ2
2-way mirror
raidZ1 (most likely to lose data)
This is for Mean Time to Data Loss, or essentially the odds of losing
_data_ due to one (or more) drive failures. I do not know if this took
number of devices per vdev and time to resilver into account.
Non-redundant configurations were not even discussed. This information
came out of Sun (pre-Oracle) and _may_ have been traceable back to
Brendan Gregg.
Google "mttdl raidz zfs" digs up:
http://blogs.oracle.com/relling/entry/zfs_raid_recommendations_space_performance
http://blogs.oracle.com/relling/entry/raid_recommendations_space_vs_mttdl
http://blog.richardelling.com/2010/02/zfs-data-protection-comparison.html
I think the second picture is the one you were thinking of. The 3rd
link adds raidz3 data to the charts.
--
Eric D. Mudama
edmud...@bounceswoosh.org
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