Mess FS: The only way to store data is in one big mess.

Robert McKeon Mike Putney

The Problem: Being Organized

• Thousands of tiny files– Bad performance– Bad Efficiency

• RAM is cheap• The trick:

– Be different than LFS

The Solution: Making a Mess

DiskRoot block Block 1 Block 2 Block 3 Block 4

…

InodeFile data*InodeFile dataInode (directory)InodeFile dataInode…

Big Block:ValidPrevious Big BlockDirectory InfoTotal LengthDirty CounterDATA (10 MB)Next Big Block

MemoryRoot block Block 7 Block 3 Block 1 Block 2

…

Inode:FilenameValidAttributesAclStartLength

*The “.freemapfile” is the first file in the root directory.

Some Messy ResultsSequential Write Performance

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

2 4 8 16 32 64 128

256

512

1024

2048

4096

8192

1638

4

3276

8

6553

6

1310

72

Number of Files

Ave

rage

Lat

ency

(m

s)

messfs write messfs write w/o stat ext2 write (no fuse)

The Road to Uncleanliness

• Find optimal time interval and big block size• Simple Page Replacement (Random Selection)• Improve Garbage Collection• Messfs optimizations

Any Messy Questions?