On Feb 20, 2012, at 6:38 AM, Robin Axelsson wrote: > > Maybe the iostat "behavior" depends on the controller it monitors. Some > controllers such as the AMD SB950 in my case may not be as transparent with > errors as the LSI 1068e operating in IT mode. > > Still, I find this to be too much of a coincidence. It is evident that ZFS is > not very good to use without disk redundancy.
Eh? Other file systems will blissfully deliver corrupted data. Silent data corruption is a much worse fate! > I'll try to add a mirror to the system pools as soon as possible. It would be > great if there were some kind of software that could be set up to generate > .par2 files (with x% data redundancy) on-the-fly to protect files on hard > drives without disk redundancy (RAID=0). Not needed. ZFS has a copies parameter where you can set the number of redundant copies on a per-dataset basis. For example, you can set copies=2 for important data, and copies=1 (the default) for data stored on other media (eg .iso files) OTOH, par2 is a completely different architecture that is designed for transferring files reliably. par2 is not well suited for direct access to data. > I couldn't recover the image file with cp but I learned in the process that > it is possible with dd. 'dd if=infile of=outfile conv=noerror,sync' could do > it. Correct, cp will exit on a failed read. > Then I discovered ddrescue which did *exactly* what I expected cp to do. I > just entered: > > # ddrescue /path/to/corrupted/file /path/to/recovered/file > /path/to/logfile.log Good idea. > all paths were even in the same vdev. In the process the vdev became > 'DEGRADED' even though no additional corruption occurred. So I did a scrub > afterwards and 'zfs clear':ed the error afterwards. I did an fmadm repair to > tell fma about it. Perhaps I should fmadm reset zfs-diagnosis and zfs-retire > as well. Once you've recovered the data, why are you so interested in eliminating the history of the corruption? > Neither par2 nor ddrescue are included with OpenIndiana, I downloaded and > installed them manually from the opencsw.org repository. I would strongly > recommend to have such tools included with OI. par2 seems to have little traction. ddrescue can be useful, but is only applicable in rare cases. -- richard -- DTrace Conference, April 3, 2012, http://wiki.smartos.org/display/DOC/dtrace.conf ZFS Performance and Training richard.ell...@richardelling.com +1-760-896-4422 _______________________________________________ OpenIndiana-discuss mailing list OpenIndiana-discuss@openindiana.org http://openindiana.org/mailman/listinfo/openindiana-discuss
