Is the fsync() fake on FreeBSD6.1?

[Leo Huang]

Hi,

I benchmarked MySQL 4.1.18 on FreeBSD 6.1 and Debian 3.1 using Super
Smack 1.3 some days ago.

The benchmark table  is
CREATE TABLE `Account` (
  `aid` int(11) NOT NULL auto_increment,
  `name` char(20) NOT NULL default '',
  `flag` int(11) NOT NULL default '0',
  `uidcount` int(11) NOT NULL default '0',
  `balance` int(11) NOT NULL default '0',
  `point` int(11) NOT NULL default '0',
  `blocktm` int(11) NOT NULL default '0',
  `ipnum` int(10) unsigned default NULL,
  `newdate` datetime default NULL,
  PRIMARY KEY  (`aid`),
  UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

And it has 1,000,000 rows.

The SQL statement is
update Account set balance= balance + 1 where aid=?;

The result is followed:
OS           Clients        Result(queries per second)  TPS(got from iostat)
FreeBSD6.1    50               516.1                         about 2000
Debian3.1     50               49.8                          about 200

The result is surprise me. The MySQL Performance on FreeBSD6.1 is
about 10 times of on Debian3.1，and the output of iostat also shows it.

I know that MySQL uses fsync() to flush both the data and log files at
default when using innodb
engine(http://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html).
Our evaluating computer only has a 10000RPM SCSI hard disk. I think it
can do about 200 sequential fsync() calls per second if the fsync() is
real.

Is the fsync() on FreeBSD6.1 fake? I mean than the data is only
written to the drives memory and so can be lost if power goes down.
And how I can confirm this?

If the fsync() is fake, how can I get the real fsync?

Any comment is welcome!

PS:
1. Our evaluating computer is DELL PowerEdge 1650。Its hardware
configuration is followed:
	CPU: 2 * Intel Pentium III 1.33GHz 512KB Level 2 Cache(smp)
	Memory: 1024MB ECC SDRAM
	HD: SEAGATE ST336706LC（36GB Ultra160 SCSI 10000RPM）
	NIC	: Intel(R) PRO/1000 Network Connection
	
2. Some important parameters in MySQL configuration file are here:
	log-bin
	sync_binlog=1
	innodb_safe_binlog
	innodb_buffer_pool_size = 384M
	innodb_additional_mem_pool_size = 20M
	innodb_log_file_size = 100M
	innodb_log_buffer_size = 8M
	innodb_flush_log_at_trx_commit = 1
	innodb_lock_wait_timeout = 50

3. on FreeBSD6.1 the /etc/fstab is followed:
	# Device                Mountpoint      FStype  Options         Dump    Pass#
	/dev/da0s1g             /home           ufs     rw              2       2
   and the outputs of tunefs is:
   mysql-test-4# tunefs -p /home
   tunefs: ACLs: (-a)                                         disabled
   tunefs: MAC multilabel: (-l)                               disabled
   tunefs: soft updates: (-n)                                 enabled
   tunefs: maximum blocks per file in a cylinder group: (-e)  2048
   tunefs: average file size: (-f)                            16384
   tunefs: average number of files in a directory: (-s)       64
   tunefs: minimum percentage of free space: (-m)             8%
   tunefs: optimization preference: (-o)                      time
   tunefs: volume label: (-L)

4. on Debian3.1 the /etc/fstab is followed:
   # <file system> <mount point>   <type>  <options>       <dump>  <pass>
   /dev/sda9       /home           ext3    defaults        0       2