Choosing and tuning Linux file systems

[Valerie Henson <val_henson@linux.intel.com>]

Hi folks,

I foolishly signed up to give a talk at OSCON in about a month about
choosing and tuning Linux file systems for different workloads.  I
have some ideas about which file system to use when, but I'd rather
get recommendations from the experts on each file system.  Below is a
straw man outline of my current recommendations, please take a look
and comment.  I will make a summary freely available when I'm done.
At long last, I'll have an easy answer when someone asks me, "But
which file system should I use?"  Answer: "Go read this web page..."

By the way, a lot of the data on file/fs limits and the like is from:

http://en.wikipedia.org/wiki/File_systems

If it's wrong, please go check the page and update it if it's wrong.
Thanks!

Choosing a file system

Laptop: ext3 with noatime
General purpose server: ext3 or reiser
Lots of small files: reiser, ext2/3 with 1k blocks
More than ~32,000 files in one directory: XFS or reiser
Fast lookups in large directories: XFS, reiser, ext3 with htree (?)
File size more than 2TB: XFS, reiser up to 8TB
File system size more than 2TB: XFS, reiser up to 16TB
Ease of data recovery after corruption: ext2, ext3

Tuning a file system

Use "noatime" mount option
 - atime makes read workloads into random write workloads, yuck
 - This is Ubuntu installation default
 - I have a report that mutt doesn't work with this because atime is
   never updated but mtime is, maybe some kind of lazy atime is better?
 - Don't do if you want to e.g., track down hackers

Choosing journaling mode in ext3
 - Default is "ordered", usually the right choice
 - "journal" is slower but guarantees data is on-disk as well
 - "writeback" is faster but may result in garbage/security leaks in
   your file data

Choosing block size
 - You can do this at mkfs time
 - tradeoff is space wasted vs. max file/fs size (other considerations?)
 - limitation is system page size

Tuning reiser
 - I know nothing!!!  Help!

Choosing number of inodes
 - XFS, reiser dynamically allocate inodes
 - Default is fine unless you have LOTS of small files (or occasionally, only big files)
 - mke2fs -T {news,largefile,largefile4}

Laptop mode
 - I know almost nothing about this... some kind of write timeout?

-VAL