Re: Power HA and Journaling.

**WARNING** **WARNING** **WARNING**

First let me say that Stefan is correct here on what option 42 does and how it helps performance. No argument whatever..... for THAT!

BUT this thread is about PowerHA and Journaling! So think about what would happen if you had about 160Kb of journal writes cached per arm and your system fails. None of those writes made it to either of the DB or the journals. (oops!) When you come up on the mirrored system you have lost all that data! Thus option 42 would not be your best friend in this environment.

- Larry "DrFranken" Bolhuis

www.frankeni.com
www.iDevCloud.com
www.iInTheCloud.com

On 1/29/2015 12:29 PM, Stefan Tageson wrote:

Hi,

If you go all in for journalling please consider a low cost feature of xxxxSS1: #42 HA Journal performance.
When installed, and when your journals being set at JRNCACHE(*YES) it will create a memory buffer of about 160kb/disc arm.
I've been working with performance analysis for ages and my history says that you can eliminate around 25-50% of system writes by doing this. The other good thing is that the 160k buffer writes will be async writes instead of sync writes to the journal.
If you happens to run a bank drop this as there is a possibility of lose transactions still in the buffer when/if system goes south.
The default timeout ( can be changed ) is 30 seconds so during low transaction rate periods your transactions will not stay in the buffer longer than that. Most of the times when I have noticed a read/write ratio of 1 to 10 - journaling is the problem and #42 is the answer. Not SSD or flash disc.

Best regards

stefan.tageson@xxxxxxxx
M +46 732 369934

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Horn, Jim
Sent: den 29 januari 2015 17:11
To: midrange-l@xxxxxxxxxxxx
Subject: RE: Power HA and Journaling.

We had this discussion with them in the past. We managed to get buy without errors without journaling but -

I said - "why not a force ratio of 1 on the files"
they said - "too slow"
I said "why is it slower than journaling"
Received no response I could understand other than "trust us"
Anyone have an explanation I might be able to understand?

Jim

message: 5
date: Thu, 29 Jan 2015 15:43:00 +0000
from: Stefan Tageson <Stefan.Tageson@xxxxxxxx>
subject: RE: Power HA and Journaling.

Hi Rick,

Short answer: Due to the fact of Single Level Storage, many objects will reside in memory. Journaling is the way of forcing them to disc where PowerHA can replicate them.

Best regards

stefan.tageson@xxxxxxxx
M +46?732 369934