Hi, I''m planning to deploy a small file server based on ZFS, but I want to know how many disks do I need for raidz and for raidz2, I mean, which are the minimum disks required. Thank you in advance. This message posted from opensolaris.org
Hi The minimum disks for raidz is 3, ( you can fool it but it wont protect your data), and the minimum disks for raidz2 is 4. James Dickens uadmin.blogspot.com On 6/19/07, Huitzi <huitzit2000 at yahoo.fr> wrote:> Hi, > > I''m planning to deploy a small file server based on ZFS, but I want to know how many disks do I need for raidz and for raidz2, I mean, which are the minimum disks required. > > Thank you in advance. > > > This message posted from opensolaris.org > _______________________________________________ > zfs-discuss mailing list > zfs-discuss at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
Huitzi wrote:> Hi, > > I''m planning to deploy a small file server based on ZFS, but I want to > know how many disks do I need for raidz and for raidz2, I mean, which are > the minimum disks required.If you have 2 disks, use mirroring (raidz would be no better) If you have 3 disks, use 3-way mirror or raidz single parity (raidz2 would be no better than a 3-way mirror) If you have 4 disks, use 2 2-way mirrors or raidz single parity or raidz double parity --matt
I also have two trivial questions (just to be sure). Do the disks have to be equal in size for RAID-Z? In a three disks RAID-Z, can I specify which disk to use for parity? This message posted from opensolaris.org
> I also have two trivial questions (just to be sure). > Do the disks have to be equal in size for RAID-Z?Not really. But just like most raid5 implementations, only the amount of space on the smallest disk (or other storage object) can be used on all the components. The extra space on the other objects will not be used. So if one disk is much smaller than the others, you lose a lot of space. 400, 400, 450 => 3x400 => 1200 raw before overhead (lose 50 of 1250 avail) 100, 400, 450 => 3x100 => 300 raw before overhead (lose 650 of 950 avail)> In a three disks RAID-Z, can I specify which disk to use for parity?No. Even in raid-5, there is no single parity disk. The parity is spread throughout the disks. In raidz, there is also no single disk dedicated to parity. As each write occurs, it will place data and parity blocks on disk, but it will not try to place parity on any disk in particular (it will just make sure that it is different from the location holding the data). -- Darren Dunham ddunham at taos.com Senior Technical Consultant TAOS http://www.taos.com/ Got some Dr Pepper? San Francisco, CA bay area < This line left intentionally blank to confuse you. >