I'm going down a bit of a different path with my reply here. I know that all shops and their need for data are different, but hear me out.
1) You're backing up 40TB+ of data, increasing at 20-25% per year. That's insane. Perhaps it's time to look at your backup strategy no from a hardware perspective, but from a data retention perspective. Do you really need that much data backed up? There has to be some way to get the volume down. If not, you're at 100TB in just slightly over 4 years (assuming the 25% growth factor). If your data is critical, my recommendation is to go find another job and let someone else have that headache. 2) 40TB of backups is, at the best possible price, 50-1TB drives (for spares and such) - $12,500 for raw drive hardware. Enclosures add some money, as do cables and such. For mirroring, 90-1TB drives is $22,500 for the raw drives. In my world, I know yours is different, but the difference in a $100,000 solution and a $75,000 solution is pretty negligible. The short description here: you can afford to do mirrors. Really, you can. Any of the parity solutions out there, I don't care what your strategy, is going to cause you more trouble than you're ready to deal with. I know these aren't solutions for you, it's just the stuff that was in my head. The best possible solution, if you really need this kind of volume, is to create something that never has to resilver. Use some nifty combination of hardware and ZFS, like a couple of somethings that has 20TB per container exported as a single volume, mirror those with ZFS for its end-to-end checksumming and ease of management. That's my considerably more than $0.02 On Thu, Jul 3, 2008 at 11:56 AM, Bob Friesenhahn < [EMAIL PROTECTED]> wrote: > On Thu, 3 Jul 2008, Don Enrique wrote: > > > > This means that i potentially could loose 40TB+ of data if three > > disks within the same RAIDZ-2 vdev should die before the resilvering > > of at least one disk is complete. Since most disks will be filled i > > do expect rather long resilvering times. > > Yes, this risk always exists. The probability of three disks > independently dying during the resilver is exceedingly low. The chance > that your facility will be hit by an airplane during resilver is > likely higher. However, it is true that RAIDZ-2 does not offer the > same ease of control over physical redundancy that mirroring does. > If you were to use 10 independent chassis and split the RAIDZ-2 > uniformly across the chassis then the probability of a similar > calamity impacting the same drives is driven by rack or facility-wide > factors (e.g. building burning down) rather than shelf factors. > However, if you had 10 RAID arrays mounted in the same rack and the > rack falls over on its side during resilver then hope is still lost. > > I am not seeing any options for you here. ZFS RAIDZ-2 is about as > good as it gets and if you want everything in one huge pool, there > will be more risk. Perhaps there is a virtual filesystem layer which > can be used on top of ZFS which emulates a larger filesystem but > refuses to split files across pools. > > In the future it would be useful for ZFS to provide the option to not > load-share across huge VDEVs and use VDEV-level space allocators. > > Bob > ====================================== > Bob Friesenhahn > [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ > GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > -- chris -at- microcozm -dot- net === Si Hoc Legere Scis Nimium Eruditionis Habes
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