RE: Performance tuning

Joe:

That's because the method it uses to speed up journaling is cache in memory, and it writes to disk when it gets a chance. On a really busy system that might cause a delay of the journal receiver being written to storage, and if the system crashes right in that instance, the journals would not be complete.

Understanding that and accepting it are a core knowledge point in system management. For the truly paranoid, and ultra careful, I would not use this except in a PowerHA environment with external disk.

For a the rest of us, it works great.


--
Jim Oberholtzer
Agile Technology Architects

-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxx> On Behalf Of Joe Pluta
Sent: Monday, December 03, 2018 9:56 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: Performance tuning

There is a lot of discussion in the help text about how this sort of caching "may not be suitable for interactive jobs where single system recovery is the primary reason for using journaling". But that by definition seems to mean that it's okay when you're in an HA environment.

On 12/3/2018 9:03 AM, Darren Strong wrote:

This is also referred to as journal caching, if you're searching for
information on it. Its activated with the JRNCACHE(*YES) function in
CHGJRN, once you purchase the option. In summary, journal data is
cached into memory before writing to disk in larger chunks, rather
than making sure its written at every change. It makes a big
difference on journaled file write/update performance.





From: "Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>
To: midrange-l@xxxxxxxxxxxx
Date: 12/02/2018 01:06 PM
Subject: Re: Performance tuning
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



Yes, we've already gone to SSD, Rob, so that particular ship has
already sailed. :) However, I am unfamiliar with HA Journal
Performance. We use MIMIX; I wonder if this is something I should be looking into.
Heck, for all I know we already have it, but it definitely sounds like
something I should look into.

On 11/30/2018 12:31 PM, Rob Berendt wrote:

Sometimes throwing money at hardware isn't always the answer. Our
original foray into SSD's was a big disappointment. Much less money
for

a

much larger return on investment would have been to buy the "HA
Journal Performance" option as part of SS1. I daresay it will be a
rare consultant who can pinpoint WHY you might need that and predict
how much it will help.


Rob Berendt

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