> Everything I've seen you should stay around 6-9 > drives for raidz, so don't do a raidz3 with 12 > drives. Instead make two raidz3 with 6 drives each > (which is (6-3)*1.5 * 2 = 9 TB array.)
So the question becomes, why? If it's performance, I can live with lower IOPS and max throughput. If it's reliability, I'd like to hear why. I would think that the number of acceptable devices in a raidz would scale somewhat with the number of drives used for parity. So I would expect to see a sliding scale somewhat like the one mentioned before regarding disk size vs. raidz level. For example: 3-4 drives: raidz1 4-8 drives: raidz2 8+ drives: raidz3 In practice, I would expect to see some kind of chart with number of devices and size of devices used together to determine the proper raidz level. Perhaps I'm way off base though. Note that I don't really have a problem doing 2 arrays, but I would think that perhaps raidz2 would be acceptable in that configuration. The benefit to that config for me would be that I could create a parallel array of 6 to copy my existing data to, then add the second array after the initial file copy/scrub. I would need fewer disks to complete the transition. > As for whether or not to do raidz, for me the > issue is performance. I can't handle the raidz > write penalty. If I needed triple drive protection, > a 3way mirror setup would be the only way I would > go. I don't yet quite understand why a 3+ drive > raidz2 vdev is better than a 3 drive mirror vdev? > Other than a 5 drive setup is 3 drives of space > when a 6 drive setup using 3 way mirror is only 2 > drive space. I've already stipulated that performance is not the primary concern. 100MB/sec with reasonable random I/O for a max of 5 clients is more than enough. My existing raidz is more than fast enough for my needs, and I have 5400RPM drives in there. I'd be very interested to hear an expert opinion on this. Given, say, 6 disks. What advantage in reliability, if any, would a raidz3 have vs. a striped pair of 3-way mirrors? Obviously the raidz3 has 1 disk worth of extra space, but we're talking about reliability here. I would guess performance would be higher with the mirrors. With all of my comments, please keep in mind that I am not a huge enterprise customer with loads of money to spend on this. If I were, I'd just buy Thumpers. I'm a home user with a decent fileserver. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
