Brian Bockelman wrote:
* When one disk goes out, the datanode shuts down - meaning that 48 disks go out. This is to be fixed in 0.21.0, I think.
That's right, though the NN doesn't report it, and I think once offline, that disk stays offline.
There's been discussion on a new JIRA issue regarding hotswap support, can I pull a disk out, plug in a new one and expect it to be possible to have the replacement brought in. You don't want to shut down 48TB just to replace one disk.
To be done properly, you really need a way to tell HDFS what you are doing, to make sure that any underreplicated data is pulled off that HDD onto the remaining disks, pause, kill the tasktracker. Once the new disk is inserted and mounted, it needs to be repopulated with blocks
-steve
