LGWR Generate tracefile: Warning: log write time 5xxms

Found tracefile db1_lgwr_3069.trc, and below error after patched database to 10.2.0.4

Oracle process number: 11
Unix process pid: 3069, image: oracle@db01 (LGWR)
.
.
.
Warning: log write time 520ms, size 1KB
*** 2008-08-31 04:17:58.951
Warning: log write time 520ms, size 6KB
*** 2008-09-21 05:03:09.770
Warning: log write time 500ms, size 3KB
*** 2008-09-23 05:07:21.534
Warning: log write time 520ms, size 2KB
*** 2008-09-25 05:04:11.367
Warning: log write time 500ms, size 3KB
*** 2008-10-04 02:04:21.518
Warning: log write time 520ms, size 3KB
*** 2008-10-08 02:06:13.150
Warning: log write time 530ms, size 2KB
*** 2008-10-16 00:09:23.470
Warning: log write time 580ms, size 2KB
*** 2008-10-16 00:56:44.111
Warning: log write time 540ms, size 6KB
*** 2008-10-16 02:24:19.342
Warning: log write time 510ms, size 3KB
*** 2008-10-16 02:55:03.864
Warning: log write time 510ms, size 2KB
*** 2008-10-24 02:21:03.037
Warning: log write time 510ms, size 2KB

when found out this error on metalink(601316.1), they tell this problem can occur on any platform, after upgrading to 10.2.0.4

And This warning message will be generated only if the log write time is more than 500 ms.

Anyway this problem tell us and we should check the disk is slow or not... and OS problem.

If everything OK... So, we can ignore these messages.