Here's a strace -r on IDE:
0.001488 write(3, "\214\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000516 fdatasync(0x3) = 0
0.001530 write(3, "\215\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000513 fdatasync(0x3) = 0
0.001555 write(3, "\216\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000517 fdatasync(0x3) = 0
0.001494 write(3, "\217\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000515 fdatasync(0x3) = 0
0.001495 write(3, "\220\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000522 fdatasync(0x3) = 0
Here it is on SCSI:
0.049285 write(3, "\3\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000689 fdatasync(0x3) = 0
0.049148 write(3, "\4\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000516 fdatasync(0x3) = 0
0.049318 write(3, "\5\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
0.000516 fdatasync(0x3) = 0
0.049343 write(3, "\6\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Looks like a constant 50ms delay on each fdatasync() on SCSI vs .5ms for
IDE. Maybe IDE isn't really doing a sync?? I find .5ms to be a little too
good.
I did this on 4 different machines with different SCSI cards (include RAID5
and non-RAID), disks, and IDE drives with the same behavior.
________________________________________
Michael D. Black Principal Engineer
[EMAIL PROTECTED] 321-676-2923,x203
http://www.csihq.com Computer Science Innovations
http://www.csihq.com/~mike My home page
FAX 321-676-2355
----- Original Message -----
From: "Jeremy Hansen" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Friday, March 02, 2001 11:27 AM
Subject: scsi vs ide performance on fsync's
We're doing some mysql benchmarking. For some reason it seems that ide
drives are currently beating a scsi raid array and it seems to be related
to fsync's. Bonnie stats show the scsi array to blow away ide as
expected, but mysql tests still have the idea beating on plain insert
speeds. Can anyone explain how this is possible, or perhaps explain how
our testing may be flawed?
Here's the bonnie stats:
IDE Drive:
Version 1.00g ------Sequential Output------ --Sequential
Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per
Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
jeremy 300M 9026 94 17524 12 8173 9 7269 83 23678 7 102.9
0
------Sequential Create------ --------Random
Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delet
e--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP
16 469 98 1476 98 16855 89 459 98 7132 99 688
25
SCSI Array:
Version 1.00g ------Sequential Output------ --Sequential
Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per
Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
orville 300M 8433 100 134143 99 127982 99 8016 100 374457 99
1583.4 6
------Sequential Create------ --------Random
Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delet
e--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP
16 503 13 +++++ +++ 538 13 490 13 +++++ +++ 428
11
So...obviously from bonnie stats, the scsi array blows away the ide...but
using the attached c program, here's what we get for fsync stats using the
little c program I've attached:
IDE Drive:
jeremy:~# time ./xlog file.out fsync
real 0m1.850s
user 0m0.000s
sys 0m0.220s
SCSI Array:
[root@orville mysql_data]# time /root/xlog file.out fsync
real 0m23.586s
user 0m0.010s
sys 0m0.110s
I would appreciate any help understand what I'm seeing here and any
suggestions on how to improve the performance.
The SCSI adapter on the raid array is an Adaptec 39160, the raid
controller is a CMD-7040. Kernel 2.4.0 using XFS for the filesystem on
the raid array, kernel 2.2.18 on ext2 on the IDE drive. The filesystem is
not the problem, as I get almost the exact same results running this on
ext2 on the raid array.
Thanks
-jeremy
--
this is my sig.
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