[Lustre-discuss] Unable to write to filesystem (device full)

[Brian J. Murrell]

On Tue, 2009-09-29 at 13:30 +0200, Nick Jennings wrote:
> Now I wish
> I hadn't added that 50G to the existing MDT slice, because it seems like
> I can't incorporate it into the MDT filesystem, and can't remove it from
> the Logical Volume (warns of data loss and I don't want to take that
> chance).

The data loss it's warning about is data that would be in the portion
you are discarding in the reduce operation.  Obviously if you have not
written anything there, there is nothing to lose.  But indeed, it's your
call.

>  So I've got about 80G left on this server, Ideally I'd like to use both
> partitions together 80G+90G for the new MDT slice, and format it using
> 2096 bytes for each inode.

2048 or 4096?

>  If I use half the default recommended setting of 2096 bytes per inode,
> will performance degrade substantially?

That depends on how well your current inode allocation is suiting your
filesystem usage.  Ideally you can analyze your current usage and
determine your optimum inode size, assuming your usage is going to
continue along the same lines.  Ultimately, for best performance, you
want to make your inodes big enough to fill a fully striped file -- at a
cost of space.  But on the other hand, if only a small percentage of
files were widely striped, you might decide that for the perhaps only
few files that are, they can suffer a bit of performance for the overall
space savings.  Again, a call you have to make yourself.

b.

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