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From Konstantin Shvachko <...@yahoo-inc.com>
Subject Re: minor change in dataNode handling of multiple directories.
Date Thu, 30 Nov 2006 18:08:55 GMT
Good point.
I think we should document it (Javadoc?) making it a feature rather than 
a side effect.

Bryan A. P. Pendleton wrote:

> I would prefer this proposal not be implements. The current way things 
> work
> makes it possible to configure, centrally, a list of all directories that
> _could_ be used for storage. Since there's no easy way to do per-node
> configurations (nor would it be desirable, IMO, in this case), the
> directories config ends up being the list of all possibly usable
> directories. Many of my cluster nodes are configured using 
> "rocksclusters":
> they will have a uniform set of mounts created, one for each physical 
> drive,
> at boot/re-install. If I specify in my config the list of all 
> directories up
> to the most number of drives a machine will ever have, then I get easy
> drop-in use, regardless of variations in nodes in the cluster. I have 
> been
> relying in the current behavior to keep me sane.
> OTOH, I wouldn't oppose making this the default behavior, with a
> configuration param that would set things back to the old behavior.
> On 11/29/06, Raghu Angadi <rangadi@yahoo-inc.com> wrote:
>> As part of the "Version upgrade" related changes, thinking of strictly
>> requiring that datanode be able to lock _all_ the configured directories
>> instead of any one of them.
>> Currently if multiple data directories are specified for a datanode, it
>> tries to lock a file is in each of the directories. If it fails to lock
>> some of the directories, it will use the directories that it could.
>> Looks like this flexibility was included mainly for convenience in
>> config file.
>> This might not affect anyone, let us know of your opinions.
>> Note that all directories have the same storage id. So each individual
>> directory is not complete by itself but a part of one storage.
>> Raghu.

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