Performance Data
-----------------
Machine:

CPU - 4 core
RAM - 24GB
OS  - SUSE 11 SP2

Configurations:

Encoding - SQL_ASCII
lc-collate - C
lc-ctype   - C

Sharedbuffers - 4GB
walbuffers    - 16MB
synchronous_commit - off
checkpoint_segments - 255
checkpoint_timeout - 25min
autovacuum - off


NORMAL DISK:
 
Head code: 

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |    1050900936 | 23.5862050056458
 ten tiny fields, all changed            |    1406130216 | 48.4863550662994
 hundred tiny fields, first 10 changed   |     621894728 | 20.3302121162415
 hundred tiny fields, all changed        |     625808144 | 19.6887240409851
 hundred tiny fields, half changed       |     629335216 | 18.9396290779114
 hundred tiny fields, half nulled        |     562484136 | 17.9967110157013
(6 rows)


lz delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     653436184 | 18.8642551898956
 ten tiny fields, all changed            |    1318515624 | 38.1201529502869
 hundred tiny fields, first 10 changed   |     460240120 | 17.8301200866699
 hundred tiny fields, all changed        |     629858848 | 22.4143190383911
 hundred tiny fields, half changed       |     626056896 | 21.9967179298401
 hundred tiny fields, half nulled        |     492390808 | 19.3679699897766
(6 rows)


lz snappy hash delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     649657360 | 17.3786590099335
 ten tiny fields, all changed            |    1325452928 | 39.5352809429169
 hundred tiny fields, first 10 changed   |     451584400 | 17.7583639621735
 hundred tiny fields, all changed        |     625361416 | 22.9972860813141
 hundred tiny fields, half changed       |     631219864 | 23.9969592094421
 hundred tiny fields, half nulled        |     468486496 | 17.7932751178741
(6 rows)


robin delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     649661736 | 18.5913350582123
 ten tiny fields, all changed            |    1320452232 | 38.9958131313324
 hundred tiny fields, first 10 changed   |     499480800 | 19.554722070694
 hundred tiny fields, all changed        |     627647648 | 20.7301239967346
 hundred tiny fields, half changed       |     624260896 | 20.2193939685822
 hundred tiny fields, half nulled        |     503203872 | 19.5177087783813
(6 rows)


TEMPFS:

Head code: 

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |    1043548048 | 10.0362451076508
 ten tiny fields, all changed            |    1398389856 | 25.9486539363861
 hundred tiny fields, first 10 changed   |     628243440 | 13.4823501110077
 hundred tiny fields, all changed        |     631385976 | 13.4999821186066
 hundred tiny fields, half changed       |     634503608 | 13.529746055603
 hundred tiny fields, half nulled        |     570543296 | 12.4785511493683
(6 rows)


lz delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     649662008 | 10.8099160194397
 ten tiny fields, all changed            |    1329584984 | 25.3514440059662
 hundred tiny fields, first 10 changed   |     462656728 | 16.0698630809784
 hundred tiny fields, all changed        |     629435064 | 16.1125748157501
 hundred tiny fields, half changed       |     633091432 | 16.2121510505676
 hundred tiny fields, half nulled        |     494109920 | 15.8088960647583
(6 rows)


lz snappy hash delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     651664720 | 8.89253091812134
 ten tiny fields, all changed            |    1315358728 | 23.7203559875488
 hundred tiny fields, first 10 changed   |     457687992 | 14.2992699146271
 hundred tiny fields, all changed        |     631983048 | 16.2922089099884
 hundred tiny fields, half changed       |     635691224 | 16.1744449138641
 hundred tiny fields, half nulled        |     471618096 | 15.859885931015
(6 rows)


robin delta encoding

                testname                 | wal_generated |     duration
-----------------------------------------+---------------+------------------
 one short and one long field, no change |     658278488 | 9.87507700920105
 ten tiny fields, all changed            |    1321909824 | 24.2310049533844
 hundred tiny fields, first 10 changed   |     512361928 | 15.4073419570923
 hundred tiny fields, all changed        |     625562392 | 16.0129189491272
 hundred tiny fields, half changed       |     629205280 | 15.9203469753265
 hundred tiny fields, half nulled        |     508250704 | 13.6569330692291
(6 rows)