I'm looking at the statfs state machine on the client based on this
users's questions. It looks like there's a bug in that sm, because
we just do a statfs to each of the servers (both IO and metadata).
If the metadata and IO nodes are split, and the storage on the
metadata nodes has a smaller capacity (i could imagine cases where it
was much smaller), then the df results will be pretty inaccurate
(since its the smallest capacity server * number of servers).
-sam
Begin forwarded message:
From: Sam Lang <[EMAIL PROTECTED]>
Date: February 2, 2007 4:28:38 PM CST
To: Sam Lang <[EMAIL PROTECTED]>
Cc: Steve <[EMAIL PROTECTED]>, <[email protected]>
Subject: Re: [Pvfs2-users] metadata
On Feb 2, 2007, at 4:15 PM, Sam Lang wrote:
On Feb 2, 2007, at 3:28 PM, Steve wrote:
Hi,
Is there any rough rule of thumb guide for the size of the
metadata for the
size of the store ?
Hi Steve,
The size of the metadata as a percent of the size of the storage
space depends on the sizes of the files. I'm doing a back of the
envelope calculation, but I think that in general, each file takes
up somewhere around 650 bytes to store its metadata, while
directories are a little less (maybe 500 bytes). Remember though
that the metadata size changes for different configurations (more
servers, etc.). There's also overhead related to the storage
space itself, which is about (100K * numservers). If you know how
many files/directories you have in your volume, you should be able
to get a rough estimate of your metadata size using those numbers
above.
I should clarify though, that the filesystem size (capacity and
available) reported by df for PVFS volumes is just the sum of the
sizes on each of the IO servers (capacity is actually the min of
all servers * numservers). This means that what df reports in
terms of usage can be inaccurate if the PVFS storage on the IO
nodes is shared with other files.
-sam
-sam
Steve
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