Bob Friesenhahn wrote: > On Tue, 16 Dec 2008, Reed Gregory wrote: > >> 8 Hardware RAID-5 Groups ( 5 drives each) and 2 SAN hot spares. >> zraid of these 8 Raid Groups. ~ 14TB usable. >> >> I did read in a FAQ that doing double redundancy is not recommended >> since parity would have to be calculated twice. I was wondering >> what the alternatives are here. > > Parity calculations are in the noise. You are reading the wrong FAQs. > It is likely that if you take care that you can carve out individual > disks as RAID-0 volumes. Then you can provide ZFS with individual > access to all the disks and ZFS can do the RAID. That is what I did. > Not one problem in 11 months. > >> Not doing ZFS redundancy means I lose the checksum abilities. Is >> that a good trade off instead of doing the double redundancy? > > ZFS checksums are independent of redundancy. Without redundancy ZFS > is not able to automatically repair the bad data. > > Bob
The older model ATABeast could only do 32 luns per controller I think but the specs say that the SATABeast: Supports up to 256 LUNS per controller. So you could do a separate RAID 0 lun per drive (as Bob suggests above) if the interface allows that - it should. You could do 6 raidz2 vdevs of 6 disks each, 2 spares and a couple of cache disks or 8 raidz2 vdevs of 5 drives each and 2 spares. Or if that doesn't work, what about doing 10 RAID 0 groups of 4 drives each on the beast (leaving the 2 spares) and then doing 2 raidz2 vdevs (5 RAID 0 groups each) from those. The beast software will send error reports on failing drives, etc so be sure to turn all those bells and whistles on - I think I had the built in testing run once per month. And Nexsan overnighted a drive when I needed a replacement. Some of the Nexsan systems are listed as offering JBOD, but it is not listed on the SATABeast specs. They should support JBOD to cater to zfs users. I configured mine to spin down the drives when they were not in use and that feature worked well*, esp if you only backups at night or have a user base that is limited in their work hours. * except for the abject terror of typing ls and having nothing happen for a few long seconds... _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
