linux-kernel - ChunkFS - measuring cross-chunk references

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Message-ID: <2e4afe1e0704241720q3eb54e24gcd10b2026759333@mail.gmail.com>
Date:	Wed, 25 Apr 2007 05:50:55 +0530
From:	"Karuna sagar K" <karunasagark@...il.com>
To:	"Theodore Tso" <tytso@....edu>,
	"Kalpak Shah" <kalpak@...syssoft.com>, "Amit Gud" <gud@....edu>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: ChunkFS - measuring cross-chunk references

On 4/24/07, Theodore Tso <tytso@....edu> wrote:
> On Mon, Apr 23, 2007 at 02:53:33PM -0600, Andreas Dilger wrote:
.........
> It would also be good to distinguish between directories referencing
> files in another chunk, and directories referencing subdirectories in
> another chunk (which would be simpler to handle, given the topological
> restrictions on directories, as compared to files and hard links).
>

Modified the tool to distinguish between
1. cross references between directories and files
2. cross references between directories and sub directories
3. cross references within a file (due to huge file size)

Below is the result from / partition of ext3 file system:

Number of files = 221794
Number of directories = 24457
Total size = 8193116 KB
Total data stored = 7187392 KB
Size of block groups = 131072 KB
Number of inodes per block group = 16288
No. of cross references between directories and sub-directories = 7791
No. of cross references between directories and file = 657
Total no. of cross references = 62018 (dir ref = 8448, file ref = 53570)

Thanks for the suggestions.

> There may also be special things we will need to do to handle
> scenarios such as BackupPC, where if it looks like a directory
> contains a huge number of hard links to a particular chunk, we'll need
> to make sure that directory is either created in the right chunk
> (possibly with hints from the application) or migrated to the right
> chunk (but this might cause the inode number of the directory to
> change --- maybe we allow this as long as the directory has never been
> stat'ed, so that the inode number has never been observed).
>
> The other thing which we should consider is that chunkfs really
> requires a 64-bit inode number space, which means either we only allow
> it on 64-bit systems, or we need to consider a migration so that even
> on 32-bit platforms, stat() functions like stat64(), insofar that it
> uses a stat structure which returns a 64-bit ino_t.
>
>                                                - Ted
>


Thanks,
Karuna

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