On Thu, 8 Sep 2011 17:35:46 -0700, Gregory Farnum wrote:
[resend to list]
2011/9/7 huang jun :
hi,all Recently,i read the source code of PG scrub.The ceph
periodically shed_scrub if the system load is not too high. And
adminstrator can manually scrub the specified OSD or PG using cmds.
but
many questions come along with me when i got thourgh . why did ceph
need scrub? what scrub used for?
Scrubbing is intended to do a few things. First, any large storage
system
needs to periodically look at the data it's holding in order to make
sure
the data stays safe -- that the underlying hardware is still working
(and
the sectors are good), that cosmic rays haven't flipped bits, etc.
Right
now, Ceph's scrubbing is primitive: it only looks at the file sizes
and a
few other metadata attributes, and compares them to the ones it
thinks
the file should have and to what other storage nodes have.
Eventually, it
will be a great deal more involved than that, though!
Will there be some kind of cryptographic checksum used to validate the
data has not changed (i.e. Something like what GIT does internally)?
Dyweni
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