Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> can you post more verbose test results on some website, or here?
> which file system?
The filesystem is reiserfs.
1.) iozone with sync-mode
1.1.)with drbd-synchronization:
File size set to 1048576 KB
Record Size 1024 KB
SYNC Mode.
Command line used: iozone -s 1g -r 1m -o -i 0
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
1048576 1024 12348 15139
1.2.)drbd stopped on the failover server:
Command line used: iozone -s 1g -r 1m -o -i 0
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
1048576 1024 59974 55659
2.) iozone in async mode (with -o)
2.1.)with drbd-synchronization:
bernd at hamilton1 test>iozone -s 1g -r 1m -i 0
Command line used: iozone -s 1g -r 1m -i 0
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
1048576 1024 51966 39944
2.2.)drbd stopped on the failover server:
Command line used: iozone -s 1g -r 1m -i 0
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
1048576 1024 109218 97123
I guess that we have to much memory for this test (3GB), so the numbers
are slightly unrealistic for 2.2. ;)
[snip]
> > Well, so I'm asking here if someone here has an idea?
> > Somehow I would like to try using protocol A or B instead of the current
> > protocol C. Its worth a try, isn't it?
> > Is it sufficient to change the protocol in the configuration files and
> > then restart drbd?
> > Lars, referring to your mail to LINUX-HA we should use drbd-0.7.1 for any
> > other protocol than C? Thats not problem, but I don't want to reboot the
> > server with a new kernel until the weekend.
>
> lacking standardized bechmarks, we did not yet settle on the slightly
> arbitrary value we want to use to kick the lower level device on a
> secondary with proto A or B... but yes, it should already be better than
> what we have with 0.7.0.
O.k. I will try it over the weekend.
>
> in any case, using DRBD adds more latency to your setup.
> so if you have had an io latency on a normal disk that is basically
> bound by rotation freq and seektime (say, 7 ms),
> you now add in network latency and the io-latency on the second node...
> for random writes, performance degrades considerably.
Of course, but that doesn't explain why 2.6.7 did so much better.
Unfortunately I do not have any iozone benchmark numbers for 2.6.7,
maybe I have time to create them during the weekend (now that our server went
into production and since people also work over the weekend, my group
won't like too many reboots ;) ).
>
> as I said, lacking data, I can not really comment on whether protocol A
> or B with current drbd svn (on the way to 0.7.1) will help.
>
> you need to benchmark it yourself.
> please post your findings.
O.k., I will do that. Switching between the protocols won't do any harm
to the filesystem, will it?
Cheers,
Bernd
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