hadoop-hdfs-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Allen Wittenauer <awittena...@linkedin.com>
Subject Re: HDFS drive, partition best practice
Date Tue, 08 Feb 2011 17:25:07 GMT

On Feb 8, 2011, at 7:20 AM, John Buchanan wrote:
> What we were thinking for our first deployment was 10 HP DL385's each with
> 8 2TB SATA drives.  First pair in Raid1 for the system drive, the
> remaining each containing a distinct partition and mount point, then
> specified in hdfs-site.xml in comma-delimited fashion.  Seems to make more
> sense to use Raid at least for the system drives so the loss of 1 drive
> won't take down the entire node.  Granted data integrity wouldn't be
> affected but how much time do you want to spend rebuilding an entire node
> due to the loss of one drive.  Considered using a smaller pair for the
> system drives but if they're all the same then we only need to stock one
> type of spare drive.

	Don't bother RAID'ing the system drive.  Seriously.  You're giving up performance for something
that rarely happens.  If you have decent configuration management, rebuilding a node is not
a big deal and doesn't take that long anyway.  

	Besides, losing one of the JBOD disks will likely bring the node down anyway.

> Another question I have is whether using 1TB drives would be advisable
> over 2TB for the purpose of reducing rebuild time.  

	You're over thinking the rebuild time.  Again, configuration management makes this a non-issue.

> Or perhaps I'm still
> thinking of this as I would a Raid volume.  If we needed to rebalance
> across the cluster would the time needed be more dependent on the amount
> of data involved and the connectivity between nodes?


	When a node goes down, the data and tasks are automatically moved.  So a node can be down
for as long as it needs to be down.  The grid will still be functional.  So don't panic if
a compute node goes down. :)

View raw message