Thanks for the follow-up. Lets start with normal erasure coding plugin. Here we have k data node and m parity nodes. For RDP or RAID-DP or MSR/MBR kind of erasure code the codeword is two dimensional array.
FOr example, in case of RDP Erasure code the cored is kx(k+m) array. The codeword has k rows and n columns (i.e. k + m) The first k columns represents the systematic data and the last m columns represents the parity data. Here the object to be divided into kX(k+m) symbols. The RDP Erasure code has one row parity and rests are diagonal parity. Pl. make google image for RDP Erasure Code diagram. I'm I making sense... Thanks, Syed On Mon, Feb 1, 2016 at 9:03 PM, Syed Hussain <syed...@gmail.com> wrote: > Hi, > > I've been working to develop a CEPH EC plgin for array type erasure code, > for example > RAID-DP (i.e RDP). Later I realized that I can't continue with (k+m) > format in CEPH as > like normal RS code if I want to save disk IO (or Read data). Since I > need to ready the individual symbols from each device rather that k > symbols. One "chunk" from OSD will contain k-symbols > in contiguous form. The same thing will be an issue for MSR(Minimum > Storage Regeneration) Erasure code plugin. > > As a solution I thought to consider k*k data chunk and k*m coding chunk > and use LRC kind of > layering to pass the info (in plugin) which is data chunk and coding chunk. > However, I've doubt if the decoding API will supply me the correct info on > lost chunks to get the info on lost erasure coding nodes. > > Does anybody have good solution to this issue using CRUSH map? > Could Pl. suggest any pointer or link that explain the above issue? > > Thanks, > Syed Abid Hussain > >
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