On Jul 1, 2011, at 2:08 PM, M. C. Srivas wrote: > On Thu, Jun 30, 2011 at 5:24 PM, Todd Lipcon <[email protected]> wrote: > >> >> I'd advise you to look at "stock hadoop" again. This used to be true, but >> was fixed a long while back by HDFS-457 and several followup JIRAs. >> >> If MapR does something fancier, I'm sure we'd be interested to hear about >> it >> so we can compare the approaches. >> >> -Todd >> >> > MapR tracks disk responsiveness. In other words, a moving histogram of > IO-completion times is maintained internally, and if a disk starts getting > really slow, it is pre-emptively taken offline so it does not create long > tails for running jobs (and the data on the disk is re-replicated using > whatever re-replication policy is in place). One of the benefits of > managing the disks directly instead of through ext3 / xfs / or other ... > > All these stats can be fed into Ganglia (or pushed out centrally via a text > file that can be pulled out using NFS) if historical info about disk > behavior (and failures) needs to be preserved. > > - Srivas.
While I am intrigued about how MapR performs internally, I don't think this is the forum for it. please keep MapR (and other vendor specific discussions) on their respective support forums. Thanks! Ian.
