Re: Power HA and Journaling. -- MIDRANGE-L

Just an FYI, but if you happen to use commitment control with journaling,
then $2 HA Journal performance doesn't do anything for you.

When you're using commitment control, the journal writes are automatically
bundled (cached).

Charles

On Thu, Jan 29, 2015 at 12:29 PM, Stefan Tageson <Stefan.Tageson@xxxxxxxx>
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

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