On 04/05/2011 09:00 AM, John R Pierce wrote: > > AFAIK, no standard raid modes verify parity on reads, as this would > require reading the whole slice for every random read. Only raid > systems like ZFS that use block checksuming can verify data on reads. > parity (or mirrors) are verified by doing 'scrubs' > > Further, even if a raid DID verify parity/mirroring on reads, this would > at best create a nonrecoverable error (bad data on one of the N drives > in the slice, no way of knowing which one is the bad one). > Thanks John, that's good information, something I didn't know. So I should think of RAID-5/6 parity as a mechanism for recovering from a drive fault that is more space-efficient than simple mirroring. Maybe RAID-10 with hot spares is more than "good enough" in most applications, but I do like dual parity for its ability to recover even in the face of a disk error popping up during the rebuild.
Am I being too paranoid? Too bad ZFS on Linux is still up at the fuse layer. I understand Btrfs is rolled into newer kernels and should be in CentOS-6, but I read somewhere it's not yet in stable release and has some potential issues, so I'm reluctant to try it. It won't have RAID-6-like parity for a while. The fact that Oracle has both ZFS and Btrfs under its wing is, um, "interesting". I'm only asking for the world :-) Chuck _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
