On Wed, February 11, 2009 15:51, Frank Cusack wrote: > On February 11, 2009 3:02:48 PM -0600 Tim <t...@tcsac.net> wrote:
>> It's hardly uncommon for an entire datacenter to go down, redundant >> power >> or not. When it does, if it means I have to restore hundreds of >> terabytes if not petabytes from tape instead of just restoring the files >> that were corrupted or running an fsck, we've got issues. > > Isn't this easily worked around by having UPS power in addition to > whatever the data center supplies? Well, that covers some of the cases (it does take a fairly hefty UPS to deal with 100TB levels of redundant disk). > I've been there with entire data center shutdown (or partial, but entire > as far as my gear is concerned), but for really critical stuff we've had > our own UPS. I knew people once who had pretty careful power support; UPS where needed, then backup generator that would cut in automatically, and cut back when power was restored. Unfortunately, the cut back failed to happen automatically. On a weekend. So things sailed along fine until the generator ran out of fuel, and then shut down MOST uncleanly. Best laid plans of mice and men gang aft agley, or some such (from memory, and the spelling seems unlikely). Sure, human error was a factor. But human error is a MAJOR factor in the real world, and one of the things we're trying to protect our data from. Certainly, if a short power glitch on the normal mains feed (to lapse into Brit for a second) brings down your data server in an uncontrolled fashion, you didn't do a very good job of protecting it. My home NAS is protected to the point of one UPS, anyway. But real-world problems a few steps more severe can produce the same power cut, practically anywhere, just not as often. > I don't know if that really works for 100TB and up though. That's a lot > of disk == a lot of UPS capacity. And again, I'm not trying to take away > from the fact that this is a significant zfs problem. We've got this UPS in our server room that's about, oh, 4 washing machines in size. It's wired into building power, and powers the outlets the servers are plugged into, and the floor outlets out here the development PCs are plugged into also. I never got the tour, but I heard about the battery backup system at the old data center Northwest Airlines had back when they ran their own reservations system. Enough lead-acid batteries to keep an IBM mainframe running for three hours. One can certainly do it if one wants to badly enough, which one should if the data is important. I can't imagine anybody investing in 100TB of enterprise-grade storage if the data WASN'T important! -- David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
