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



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