On Tue, Sep 30, 2008 at 03:19:40PM -0700, Erik Trimble wrote: > To make Will's argument more succinct (<wink>), with a NetApp, > undetectable (by the NetApp) errors can be introduced at the HBA and > transport layer (FC Switch, slightly damage cable) levels. ZFS will > detect such errors, and fix them (if properly configured). NetApp has no > such ability.
It sounds like you mean the Netapp can't detect silent errors in it's own storage. It can (in a manner similar, but not identical to ZFS). The difference is that the Netapp is always remote from the application, and cannot detect corruption introduced before it arrives at the filer. > Also, I'm not sure that a NetApp (or EMC) has the ability to find > bit-rot. That is, they can determine if a block is written correctly, > but I don't know if they keep the block checksum around permanently, > and, how redundant that stored block checksum is. If they don't > permanently write the block checksum somewhere, then the NetApp has no > way to determine if a READ block is OK, and hasn't suffered from bit-rot > (aka disk block failure). And, if it's not either multiply stored, then > they have the potential to lose the ability to do READ verification. > Neither are problems of ZFS. A netapp filer does have a permanent block checksum that can verify reads. To my knowledge, it is not redundant. But then if it fails, you can just declare that block bad and fall back on the RAID/mirror redundancy to supply the data. -- Darren _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
