I thought I might chime in with my thoughts and experiences. For starters, I am very new to both OpenSolaris and ZFS, so take anything I say with a grain of salt. I have a home media server / backup server very similar to what the OP is looking for. I am currently using 4 x 1TB and 4 x 2TB drives set up as mirrors. Tomorrow, I'm going to wipe my pool and go to 4 x 1TB and 4 x 2TB in two 4 disk raidz's.
I backup my pool to 2 external 2TB drives that are simply striped using zfs send/receive followed by a scrub. As of right now, I only have 1.58TB of actual data. ZFS send over USB2.0 capped out at 27MB/s. The scrub for 1.5TB of backup data on the USB drives took roughly 14 hours. As needed, I'll destroy the backup pool and add more drives as needed. I looked at a lot of different options for external backup, and decided to go with cheap (USB). I am using 1TB and 2TB WD Caviar Green drives for my storage pool, which are about the cheapest and probably close to the slowest consumer drives you can buy. I've only been at this for about 4-5 months now, and thankfully I haven't had a drive fail yet so I cannot attest to resilver times. I do weekly scrubs on both my rpool and storage pool via a script called through cron. I just set things up to do scrubs during a timeframe when I know I'm not going to be using it for anything. I can't recall the exact times it took for the scrubs to complete, but it wasn't anything that interfered with my usage (yet...) The vast majority of any streaming media I do (up to 1080p) is over wireless-n. Occasionally, I will get stuttering (on the HD stuff), but I haven't looked into whether it was due to a network or I/O bottleneck. Personally, I would think it was due to network traffic, but that is pure speculation. The vast majority of the time, I don't have any issues whatsoever. The main point I'm trying to make is that I'm not I/O bound at this point. I'm also not streaming to 4 media players simultaneously. I currently have far more storage space than I am using. When I do end up running low on space, I plan to start with replacing the 1TB drives with, hopefully much cheaper at that point, 2TB drives. If using 2 x raidz vdevs doesn't work well for me, I'll go back to mirrors and start looking at other options for expansion. I find Erik Trimble's statements regarding a 1 TB limit on drives to be a very bold statement. I don't have the knowledge or the inclination to argue the point, but I am betting that we will continue to see advances in storage technology on par with what we have seen in the past. If we still are capped out at 2TB as the limit for a physical device in 2 years, I solemnly pledge now that I will drink a six-pack of beer in his name. Again, I emphasize that this assumption is not based on any sort of knowledge other than past experience with the ever growing storage capacity of physical disks. My personal advice to the OP would be to set up three 4 x 1TB raidz vdevs, and investing in a reasonable backup solution. If you have to use the last two drives, set them up as a mirror. Redundancy is great, but in my humble opinion, for the home user that is using "cheap" hardware, it's not as critical as performance and available storage space. That particular configuration would give you more IOPS than just two raidz2 vdevs, with slightly less redundancy and slightly more storage space. For my own needs, I don't see redundancy as being as high a priority as IOPS and available storage space. Everyone has to make their own decision on that, and the ability of ZFS to accommodate a vast array of different individual needs is a big part of what makes it such an excellent filesystem. With a solid backup, there is really no reason you can't redesign your pool at a later date if need be. Try out what you think will work best, and if that configuration doesn't work well in s ome way, adjust and move on... There are a few different schools of thought on how to backup ZFS filesystems. ZFS send/receive works for me, but there are certainly weaknesses with using it as a backup solution (as has been much discussed on this list.) Hopefully, in the future it will be possible to remove vdevs from a pool and to restripe data across a pool. Those particular features would certainly be great for me. Just my thoughts. Eric -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
