Hi,
A while ago, I did some longish runs of OSDB (osdb.sf.net)
against PostgreSQL 7.2. All runs were on kernel 2.5.6 + the
dc395x driver and the futexes patch. I'd have included
reiserfs too, but in 2.5.6 it seemed to oops on mount. 2.5.7
doesn't boot for me, but I'll run these again when a more
interesting kernel appears.
Hardware is: 2 x P3-450, 384Mb, 3 x 9Gb Quantum disks on
internal aic7xxx (new driver). Except for a "vmstat 1", the
system was otherwise unused during the tests. There was no
other mounted filesystem on the disk with the test partition.
The numbers seem pretty consistent -- if they're more than 5%
different, that's probably a valid comparision (no, I'm not a
statistician and can't justify that).
The scripts I used are available on request, but they do
roughly:
stop postgres
umount
mkfs
mount
create postgres data directories
start postgres (incl. creating postgres database)
"osdb-pg --datadir /scratch/data-40mb/ --short"
"Tuning" key:
"dd" -- default PG, default FS opts
"dn" -- default PG, "noatime"
"bn" -- big PG buffers, "noatime"
PostgreSQL
tuning? single ir mx-ir oltp mixed-oltp
(sec) (tps) (sec) (tps) (sec)
ext2 dd 1304.72 66.64 214.25 188.50 230.55
dn 1288.31 65.93 209.57 234.08 213.75
bn 1283.50 77.90 1867.71 192.43 226.77
ext3 dd 1303.84 66.87 212.49 66.06 361.04
dn 1288.03 64.62 209.27 111.41 278.54
bn 1285.32 65.98 1996.41 90.05 307.79
ext3-wb dn 1291.68 66.06 209.94 138.25 242.28
bn 1287.31 98.42 2149.38 125.13 236.02
jfs dd 1308.97 66.82 212.59 117.28 273.08
dn 1288.60 65.08 211.56 116.18 218.22
bn 1279.89 81.00 2059.26 114.20 225.56
minix dd 1305.26 67.38 207.74 193.90 228.81
dn 1331.27 67.14 210.07 223.70 214.33
bn 1299.24 89.58 1988.31 231.17 231.17
My conclusions:
1. I'll have to spend more time learning to tune postgres,
but clearly something went wrong there -- the
"agg_simple_report" test accounted for almost all of the
differences.
2. "noatime" is very useful switch for these circumstances.
3. The journalled filesystems do have measurable overhead
for this workload.
Questions:
1. Is there anything else I should try in the way of fs
options, etc?
2. What does jfs do in the way of data journalling? Is it
"ordered" or "writeback", in ext3-speak? (I assume
fully journalled data would give much worse performance.)
Cheers,
Matthew.
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This archive was generated by hypermail 2b29 : Sun Mar 31 2002 - 22:00:13 EST