Frank Middleton wrote:
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...
Not that bad. Uncommitted ZFS data in memory does not tend to
live that long. Writes are generally out to media in 30 seconds.
Solaris scrubs memory, with a 12-hour cycle time, so memory does
not remain untouched for a month. For high-end systems,
memory scrubs are also performed by the memory controllers.
Beware, if you go down this path of thought for very long, you'll soon
be afraid to get out of bed in the morning... wait... most people actually
die in beds, so perhaps you'll be afraid to go to bed instead :-)
"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.
Yes, but all of the discussions in this thread can be classified as
systems engineering problems, not product design problems.
If you do your own systems engineering, then add this to your
(hopefully long) checklist.
-- richard
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
