On Jun 11, 2011, at 5:46 AM, Edward Ned Harvey wrote: >> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- >> boun...@opensolaris.org] On Behalf Of Jim Klimov >> >> See FEC suggestion from another poster ;) > > Well, of course, all storage mediums have built-in hardware FEC. At least > disk & tape for sure. But naturally you can't always trust it blindly... > > If you simply want to layer on some more FEC, there must be some standard > generic FEC utilities out there, right? > zfs send | fec > /dev/... > Of course this will inflate the size of the data stream somewhat, but > improves the reliability...
The problem is that many FEC algorithms are good at correcting a few bits. For example, disk drives tend to correct somewhere on the order of 8 bytes per block. Tapes can correct more bytes per block. I've collected a large number of error reports showing the bitwise analysis of data corruption we've seen in ZFS and there is only one case where a stuck bit was detected. Most of the corruptions I see are multiple bytes and many are zero-filled. In other words, if you are expecting to use FEC and FEC only corrects a few bits, you might be disappointed. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
