On 20 maj 2010, at 20.35, David Magda wrote: > On Thu, May 20, 2010 14:12, Travis Tabbal wrote: >>> On May 19, 2010, at 2:29 PM, Don wrote: >> >>> The data risk is a few moments of data loss. However, >>> if the order of the >>> uberblock updates is not preserved (which is why the >>> caches are flushed) >>> then recovery from a reboot may require manual >>> intervention. The amount >>> of manual intervention could be significant for >>> builds prior to b128. >> >> >> This risk is mostly mitigated by UPS backup and auto-shutdown when the UPS >> detects power loss, correct? > > Unless you have a contractor working in the server room that bumps into > the UPS and causes a power glitch which causes a whole bunch of equipment > to cycle. > > Happened at $WORK (in another office) just two weeks ago.
Or, a zillion of other problem modes with that setup, all from problems with the UPS, to the auto-shutdown communication signaling system, a problem with the computer system, the electrical distribution, or anything else. Building complex solutions to solve critical issues is IMHO seldom a very good solution. If you care about data integrity, buy stuff that do what they are supposed to do, and keep everything simple. Redundancy is often good, but keep the switchover mechanisms as simple and as few as possible. Choose mechanisms that can and will be tested regularly - and don't use systems that are almost never used and/or tested. Complex systems tend to fail, especially after some time when things have changed a bit, or even cause more outages in themselves. They are hard to test, maintain and understand, and they are often costly to buy too. KISS, you know. In the Intel X25 case - bug them until they release new firmware - they have sold you a defect product that they still haven't fixed. If they don't fix it and you need it, get another drive. > It all depends on your level of paranoia. Either that, or you may have some kind of protocol, policy, contract, SLA or similar that you have to follow. (In any case it is often really hard to even guess how much a certain change gives or takes in availability numbers.) Just my 5 öre. /ragge _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
