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 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.
Zfs development seems to be overwelmed with marketing-driven
requirements lately and it is time to get back to brass tacks and
make sure that the parts already developed are truely enterprise-
grade.
While I don't disagree that the focus for ZFS should be ensuring
enterprise-class reliability and performance, let me assure you that
requirements are driven by the market and not by marketing.
Adam
--
Adam Leventhal, Fishworks http://blogs.sun.com/ahl
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
