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aig 07-08-2004 11:09 PM

Maximum Number of Directory Entries & Performance
 
Hi Everyone,

I was wondering if anyone knows if or what the maximum number of directory entries is on an ext3 filesystem. Is this a static value or calculated?

What happens to the read/write performance of a partition as the amount of directory entries increases?

I ask because I'm working with a team to develop a digital archive that will eventually hold thousands of assets. Thanks.

~AIG

druuna 07-09-2004 08:36 AM

Inodes are calculated, the number of inodes you are left with depend on:

- Partition size,
- blocksize,
- bytes/inode ratio.

Beside the partition size, most of the time you do not alter blocksize and b/i ration. Changing these can be a good idea if you already know if files written to this partition are small/big.
I.e. lots of files with a small size (say 2k) and a 'large' blocksize (say 8k) will have a 'negative' result because for every file written (2k) a size of 8K (blocksize) is allocated on disk. You cannot access the 6K that's 'empty'.

Take a look at the manpage for mke2fs for available options.

The number of inodes do not degrade the performance. If partitons are very large there could be a sligth decrease in performance due to the 'travel' the head(s) needs to do.

Besides inodes, there are a lot more things you need to think of when tuning a box. Here are just 2:
- Can hardware do simultanious reads/writes (ide/scsi/controller),
- I/O intens or CPU intens,

Some links that could be of interrest:
http://www.nyx.net/~sgjoen/disk.html
http://www.psc.edu/networking/perf_tune.html
http://edocs.bea.com/wls/docs81/perform/HWTuning.html

Hope this helps.


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