> I'm trying to figure out some formulas for calculating bare metal storage > needed to > meet a usable storage volume goal. > > So far, my efforts have concentrated on calculating the usable/bare metal > ratio for > an 8-disk array configured for raidz2 with 1 hot spare (7 disks in the pool, > 1 spare). > > For 8 500GB disks I got a pool of 3.16TB. > > >From this I calculated that roughly 79% of my bare metal capacity is available > with raidz2 and a hot spare. > > So, I'm thinking my multiplier should be Required Usable Storage * 1.21 > > In other words, (RUS)1.21=BMS > > Where RUS is Required Usable Storage and BMS is Bare Metal Storage. Do > these numbers make sense? Has anyone done anything similar with raidz (rather > than raidz2)?
No, they do not make sense. You have 8 disks, -1 for spare, -2 for parity. That gives you 5 disks for data. 500GB * 5 is 2500GB. Disk manufacturers use 1000*1000*1000 for giga, but the system uses 1024*1024*1024. So you will get 2.3TB. ZFS overhead is not in that calculation, that depends on what you are storing. _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
