On Thu, 4 Sep 2014, ???????? wrote: > > hi, guys: > ? > ? when I read the filestore.cc, I find the ceph use crc the check the data. > Why should check the data? > > ? In my knowledge, ?the disk has error-correcting code?(ECC) for each > sector. Looking at wiki: http://en.wikipedia.org/wiki/Disk_sector, "In disk > drives, each physical sector is made up of three basic parts, the sector > header, the data area and the error-correcting code?(ECC)".? So if the data > is not correct. the disk can recovery it or ?return i/o error. > ? > ? Does anyone can explain it? These checksums are not terribly reliable, and I think not even present on all disks. Note that the CRC checks in FileStore today are opportunistic and there primarily for our QA environment; we don't recommend enabling them in production environments right now because we're not sure what the performance implications are. sage
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