Adam Leventhal wrote:
Hey Bob,
MTTDL analysis shows that given normal evironmental conditions, the
MTTDL of RAID-Z2 is already much longer than the life of the computer
or the attendant human. Of course sometimes one encounters unusual
conditions where additional redundancy is desired.
To what analysis are you referring? Today the absolute fastest you can
resilver a 1TB drive is about 4 hours. Real-world speeds might be half
that. In 2010 we'll have 3TB drives meaning it may take a full day to
resilver. The odds of hitting a latent bit error are already
reasonably high especially with a large pool that's infrequently
scrubbed meaning. What then are the odds of a second drive failing in
the 24 hours it takes to resiler?
I wish it was so good with raid-zN.
In real life, at least from mine experience, it can take several days to
resilver a disk for vdevs in raid-z2 made of 11x sata disk drives with
real data.
While the way zfs ynchronizes data is way faster under some
circumstances it is also much slower under other.
IIRC some builds ago there were some fixes integrated so maybe it is
different now.
I do think that it is worthwhile to be able to add another parity
disk to an existing raidz vdev but I don't know how much work that
entails.
It entails a bunch of work:
http://blogs.sun.com/ahl/entry/expand_o_matic_raid_z
Matt Ahrens is working on a key component after which it should all be
possible.
A lot of people are waiting for it! :) :) :)
ps. thank you for raid-z3!
--
Robert Milkowski
http://milek.blogspot.com
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