Re: Log File Syncs
From: Mladen Gogala <gogala.mladen_at_gmail.com>
Date: Sat, 26 Mar 2016 00:10:59 -0400
Message-ID: <56F60BD3.7010306_at_gmail.com>
On 03/24/2016 12:53 PM, Osborne, Chris wrote:
>
> The log file write time is also slightly faster on the ‘slow’ DB
> leading me to believe that IO is not an issue.
>
Chris, the obvious answer is in the different versions of Linux. RH 5.x is running an ancient kernel 2.6.18 while CentOS 6.6 is running much newer kernel 3.10. I don't know the underlying file systems, but I know that Red Hat 5.x did not support Ext4, while CentOS 6.x does support it, it's a default FS in that version.
There is a huge difference between those two file systems, one is block based, another one is extent based. Block based file systems turn the vast majority of IO into random access IO, while extent based file systems can write sequentially, as is the nature of log file writes. So, my two obvious candidates for the differences are much newer kernel and different file system.
Regards
Date: Sat, 26 Mar 2016 00:10:59 -0400
Message-ID: <56F60BD3.7010306_at_gmail.com>
On 03/24/2016 12:53 PM, Osborne, Chris wrote:
>
> The log file write time is also slightly faster on the ‘slow’ DB
> leading me to believe that IO is not an issue.
>
Chris, the obvious answer is in the different versions of Linux. RH 5.x is running an ancient kernel 2.6.18 while CentOS 6.6 is running much newer kernel 3.10. I don't know the underlying file systems, but I know that Red Hat 5.x did not support Ext4, while CentOS 6.x does support it, it's a default FS in that version.
There is a huge difference between those two file systems, one is block based, another one is extent based. Block based file systems turn the vast majority of IO into random access IO, while extent based file systems can write sequentially, as is the nature of log file writes. So, my two obvious candidates for the differences are much newer kernel and different file system.
Regards
-- Mladen Gogala Oracle DBA Tel: (347) 321-1217 -- http://www.freelists.org/webpage/oracle-lReceived on Sat Mar 26 2016 - 05:10:59 CET