Richard Elling
Sun, 19 Jul 2009 15:11:19 -0700
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^-12error/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