Firebird + EXT4 + barrier 1/0 + FW ON/OFF

Philippe Makowski did some TPC tests and posted the results at fb-devel:

Hi,

I’m a bit puzzled by the results I get I made test on Fedora 16 with Kernel 3.1.1-1.fc16.x86_64 on LVM2 Logical Volume of 10G

Firebird 2.5.1 Classic

hdparm  /dev/vg_tests/testfb
/dev/vg_tests/testfb:
multcount     =  0 (off)
IO_support    =  1 (32-bit)
readonly      =  0 (off)
readahead     =  8 (on)

hdparm -Tt /dev/vg_tests/testfb
/dev/vg_tests/testfb:
Timing cached reads:   12976 MB in  2.00 seconds = 6496.46 MB/sec
Timing buffered disk reads: 174 MB in  3.02 seconds =  57.53 MB/sec

database : 1,8G
created with -w20
and buffers 1024

tpcc lanched with -a1 -b1 -W20 -T20 -r1 -R10 -i60
protocol TCP/IP

Scheduler was cfq (deadline scheduler results are really close)

First, on this box (certainly because Fedora 16 use ext4 driver only) ext3 give bad results

so on a database with -write async
for ext4

noatime,async,data=ordered,barrier=1
TPC-C Throughput: 5467.10 tpmC

noatime,async,data=ordered,barrier=0
TPC-C Throughput: 5427.88 tpmC

sync,data=ordered,barrier=0
TPC-C Throughput: 562.11 tpmC

for a raw device
TPC-C Throughput: 6604.00 tpmC

with -write sync
for ext4

noatime,async,data=ordered,barrier=1
TPC-C Throughput: 165.11 tpmC

noatime,async,data=ordered,barrier=0
TPC-C Throughput: 566.89 tpmC

sync,data=ordered,barrier=0
TPC-C Throughput: 568.11 tpmC

for a raw device
TPC-C Throughput: 396.78 tpmC

So reliability have a real cost
hard to have perf and reliability
I really wonder if we can’t get MaxUnflushedWrites or something like
that under Linux too
I would be curious to do same test with this parameter under Linux

it will not be really safe, but at least a medium solution for people
because between
5467.10 tpmC (FW OFF and noatime,async,data=ordered,barrier=1)
and
165.11 tpmC (FW ON and noatime,async,data=ordered,barrier=1)
seems that there is a room

Update:

with FW OFF and MaxUnflushedWrites = 100 and MaxUnflushedWriteTime = 5
ext4
noatime,async,data=ordered,barrier=1
TPC-C Throughput: 1155.67 tpmC

as expected between
5467.10 tpmC (FW OFF and noatime,async,data=ordered,barrier=1)
and
165.11 tpmC (FW ON and noatime,async,data=ordered,barrier=1)

but only partially reliable 🙁