> -----Original Message----- > From: Darren J Moffat [mailto:darr...@opensolaris.org] > > It's one of the big selling points, reasons for ZFS to exist. You > should > > always give ZFS JBOD devices to work on, so ZFS is able to scrub both > of the > > redundant sides of the data, and when a checksum error occurs, ZFS is > able > > to detect *and* correct it. Don't use hardware raid. > > That isn't the recommended best practice, you are stating it far too > strongly. > > The recommended best practice is to always create ZFS pools with > redundancy in the control of ZFS. That doesn't require that the back > end storage be JBOD or full disks nor does it require you not to use > hardware raid. Some of all of which are impossible if you are using SAN > or other remote block storage devices in many cases - and certainly the > case if the SAN is provided by a Sun ZFS Storage appliance.
You're right though, I'm stating that too strongly. Never say never. And never say always. The truth is exactly as you said. Even if you have redundancy in hardware, make sure you also have redundancy in ZFS. If you allow hardware to manage redundancy ... Then just as Budy has experienced, when corruption is found, it's not consistently repeatable, and it could appear anywhere in the storage unit randomly. ZFS is unable to isolate the individual failing disk. After enough checksum failures, the whole storage unit will be marked failed and taken offline. So much for your redundancy. It is a problem if your only redundancy is hardware. It is not a problem if you also have redundancy managed by ZFS. So a more correct conclusion would be "Whenever possible" don't use hardware raid, and "whenever possible" use JBOD managed by ZFS. But whatever you do, make sure ZFS has some redundancy it can manage. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
