Re: [9fans] KFS magic size?

[Geoff Collyer <geoff@collyer.net>]

To elaborate on anothy's note, here's a summary of the situation that
I wrote a few years ago:

The maximum size of a single file in a kfs (or plan 9 file server)
file system is determined by the file system block size (there are
single and double indirect blocks but no triples).  The maximum size
is approximately (blocksize/512)⁳*8 megabytes or, more accurately,
(6+x+x⁲)*d bytes, where d=blocksize-8 and x=d/4:

blksize	max. file size in MB	in bytes
512	7.69			8068032
1024	62.76			65812416
1536	213.20			223564736
2048	507.02			531656640
2560	992.22			1040419776
3072	1716.79			1800185792
3584	2728.73			2861286336
4096	4076.05			4274053056

In addition, at the time of writing (April 1999), the file server and
kfs use 32-bit integers internally to hold file sizes and offsets and
some of those integers are signed, so the practical limit on the size
of a single file is 2⁳ⁱ-1 bytes (roughly 2GB).