On Tue, Mar 29, 2011 at 08:44:24PM +0100, Chris Lee wrote: > > On 29/03/11 16:29, Jon LaBadie wrote: > >On Tue, Mar 29, 2011 at 10:26:29AM -0400, Chris Hoogendyk wrote: > >> > >>On 3/29/11 10:00 AM, Charles Curley wrote: > >>>On Tue, 29 Mar 2011 12:01:49 +0100 > >>>Chris Lee<[email protected]> wrote: > >>> > >>>>I was just thinking about my virtual tapes and the chances of a > >>>>failed sector or two going un-noticed until I needed to restore my > >>>>data. > >>>Modern hard drives handle bad sectors for you transparently. They swap > >>>in a spare sector, without notifying you. The only way you will see a > >>>report is if the hard drive runs out of spare sectors. If you see a bad > >>>sector report, you have worse problems than a bad backup. Go buy a > >>>replacement drive immediately. > >>> > >>>If you are concerned about the reliability of your hard drives, look > >>>into smartmontools. It uses the drive's firmware to test and collect > >>>data. Unfortunately sometimes the reports can be rather cryptic to the > >>>non-hard-drive-literate. > >>Or go with ZFS on Solaris or FreeBSD or ... see > >>http://en.wikipedia.org/wiki/ZFS#Platforms. > >> > >>See http://www.zdnet.com/blog/storage/zfs-data-integrity-tested/811 > >I think BtrFS also checksums data and metadata. > > > >jon > > > > All the file systems and hard drives only "fix" a problem if they > happen to read the data and find the problem. > What happens while those backups are just sitting there for months > with no one reading them, then we read it and find out there is just > not enough left to repair anything. > It only takes a stray cosmic particle to take out enough data to > make a good backup not good enough, and I would rather know about it > before I need it.
If your checksum application detects an error, would you be able to fix it? Probably not. If you still have the original, you could back it up again. But ZFS automatically gives you back corrected data for 1-bit, and I think, 2-bit errors. jl -- Jon H. LaBadie [email protected] JG Computing 12027 Creekbend Drive (703) 787-0884 Reston, VA 20194 (703) 787-0922 (fax)
