On Thu, May 15, 2014 at 07:00:10PM +1000, Russell Coker wrote: > http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.html > > Page 13 of the above paper says: > > # Figure 12 presents for each block number, the number of disk drives of disk > # model ‘E-1’ that developed a checksum mismatch at that block number. We see > # in the figure that many disks develop corruption for a specific set of block > # numbers. We also verified that (i) other disk models did not develop > # multiple check-sum mismatches for the same set of block numbers (ii) the > # disks that developed mismatches at the same block numbers belong to > # different storage systems, and (iii) our software stack has no specific data > # structure that is placed at the block numbers of interest. > # > # These observations indicate that hardware or firmware bugs that affect > # specific sets of block numbers might exist. Therefore, RAID system designers > # may be well-advised to use staggered stripes such that the blocks that form > # a stripe (providing the required redundancy) are placed at different block > # numbers on different disks. > > Does the BTRFS RAID functionality do such staggered stripes? If not could it > be added?
Yes, it could, by simply shifting around the chunk locations at allocation time. I'm working in this area at the moment, and I think it should be feasible within the scope of what I'm doing. I'll add it to my list of things to look at. Hugo. > I guess there's nothing stopping a sysadmin from allocating an unused > partition at the start of each disk and use a different size for each disk. > But I think it would be best to do this inside the filesystem. > > Also this is another reason for having DUP+RAID-1. > -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- If you're not part of the solution, you're part --- of the precipiate.
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