Brian, When you say *attempt* to complete and *entire* node scan, you mean for example, if a node has 100 block files, it will try to verify all 100 block every 3 weeks? That is in average, a block is scanned every (3 weeks / 100 time interval)?
Thanks Thanh On Wed, Oct 13, 2010 at 7:07 PM, Brian Bockelman <bbock...@cse.unl.edu>wrote: > Hi Thanh, > > The scan period is the period that hadoop *attempts* to complete an entire > node scan. That is, if it's set to 3 weeks, HDFS will try to scan each > block once every 3 weeks. > > Obviously, depending on the bandwidth you have made available to the > scanning thread, you can specify impossibly small periods. > > Brian > > On Oct 13, 2010, at 7:01 PM, Thanh Do wrote: > > > Hi again, > > > > Could any body explain to me about the scanning period > > policy of DataBlockScanner? That is who often it wake up > > and scan a block file. > > When looking at the code, I found > > > > static final long DEFAULT_SCAN_PERIOD_HOURS = 21*24L; // three weeks > > > > > > but definitely it does not wake up and pick a random block > > to verify every three weeks, right? > > > > Thanks a lot, > > Thanh > >
