On 07/19/09 05:00 AM, dick hoogendijk wrote:
(i.e. non ECC memory should work fine!) / mirroring is a -must- !
Yes, mirroring is a must, although it doesn't help much if you
have memory errors (see several other threads on this topic):
http://en.wikipedia.org/wiki/Dynamic_random_access_memory#Errors_and_error_correction
"Tests[ecc]give widely varying error rates, but about 10^-12
error/bit·h is typical, roughly one bit error, per month, per
gigabyte of memory."
That's roughly 1 per week in 4GB. If 1 error in 50 results in a ZFS
hit, that's one/year per user on average. Some get more, some get
less.That sounds like pretty bad odds...
"In most computers used for serious scientific or financial computing
and as servers, ECC is the rule rather than the exception, as can be
seen by examining manufacturers' specifications." Sun doesn't even
sell machines without ECC. There's a reason for that.
IMO you'd be nuts to run ZFS on a machine without ECC unless
you don't care about losing some or all of the data. Having
said that, we have yet to lose an entire pool - this is pretty
hard to do! I should add that since setting copies=2 and forcing
the files to be copied, there have been no more unrecoverable
errors on a particularly low end machine that was plagued with
them even with mirrors (and a UPS with a bad battery :-) ).
On 19-Jul-09, at 7:12 AM, Russel wrote:
As this was not clear to me. I use VB like others use vmware
etc to run solaris because its the ONLY way I can,
Given that PC hardware is so cheap these days (used SPARCS
even cheaper), surely it makes far more sense to build a nice
robust OSOL/ZFS based file server *with* ECC. Then you can use
iscsi for your VirtualBox VMs and solve all kinds of interesting
problems. But you still need to do backups. My solution for
that is to replicate the server and backup to it using zfs
send/recv. If a disk fails, you switch to the backup and no
worries about the second disk of the mirror failing during a
resilver. A small price to pay for peace of mind.
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