Re: [zfs-discuss] Re: Big JBOD: what would you do?
Rich Teer wrote: On Sat, 22 Jul 2006, Richard Elling wrote: This one stretches the models a bit. In one model, the MTTDL is For us storage newbies, what is MTTDL? I would guess Mean Time To Data Loss, which presumably is some multiple of the drives' MTBF (Mean Time Between Failures)? Correct, MTTDL = Mean Time To Data Loss MTBF = Mean Time Between Failures MTTR = Mean Time To Recover MTBS = Mean Time Between Services (eg. repair action) MTBSI = Mean Time Between Service Interruption When we talk about retention, we worry about MTTDL. When we talk about data availability, we worry about MTBSI. When we talk about spares stocking or service intervals, MTBS. Systems architecture, component selection, and configuration all interact with each other. It would be nice to have some really good dependability benchmarks to apply, but that discipline is still in its early stages. -- richard ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Re: Big JBOD: what would you do?
Thanks Rob, one comment below. Rob Logan wrote: perhaps these are good picks: 5 x (7+2) 1 hot spare 35 data disks - best safety 5 x (8+1) 1 hot spare 40 data disks - best space 9 x (4+1) 1 hot spare 36 data disks - best speed 1 x (45+1) 0 hot spare 45 data disks - max space This one stretches the models a bit. In one model, the MTTDL is ~1200 years and in a more detailed model, it is 6 years. Most people will be very unhappy with an MTTDL of 6 years. To put this in perspective, a 46-disk RAID-0 has an MTTDL of less than 2 years in all models. I'd like to hear from the ZFS team how such a wide stripe would be expected to perform :-) -- richard ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
[zfs-discuss] Re: Big JBOD: what would you do?
This gives a nice bias towards one of the following configurations: - 5x(7+2), 1 hot spare, 17.5TB [corrected] - 4x(9+2), 2 hot spares, 18.0TB - 6x(5+2), 4 hot spares, 15.0TB In addition to Eric's suggestions, I would be interested in these configs for 46 disks: 5 x (8+1)1 hot spare20.0 TB 4 x (10+1) 2 hot spares 20.0 TB 6 x (6+1)4 hot spares 18.0 TB In a few cases, we might want more space rather than 2-disk parity. Thanks. This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss