RE: journalling overhead

[Kevin H <kevinh@xxxxxxxxxxx>]

Phil -

herewith my observations regarding journaling -
made at a client who uses journaling in a real aggressive manner.


1) On Startup, journaling selects the fastest (up to 6) heads in an ASP
2) Then, when running, it is not subject to "disk balancing" as we 
know/knew it <by % used>,
    but <for speed of writing purposes, just does sequential writes.
    That is why, given enough heads in an ASP, it may be beneficial to move 
Journaling to it's own ASP.

On the WRKDSKSTS screen,
I have seen the journaling disks at close to 100% busy,
and even seen them overflow 100% full while the other disks are sitting at 55%.

So, the potential for performance impact is there.
I believe there observations were made at v4r4,
and I am not sure which changes have come in since then...

just my observations..hope they help

kmh

At 08:20 AM 6/6/2001, you wrote:
>Al,
>
>This machine is at V4R5.  But there is only one ASP.
>
>Phil
>
>-----Original Message-----
>From: owner-midrange-l@midrange.com [mailto:owner-midrange-l@midrange.com]On
>Behalf Of barsa@barsaconsulting.com
>Sent: Wednesday, June 06, 2001 6:16 AM
>To: MIDRANGE-L@midrange.com
>Subject: Re: journalling overhead
>
>
>Not likely, unless you are using the read journaling implemented in V5R1.
>The removal of the performance problems with journaling is heavily based on
>the premise that the journal receiver is in a dedicated User ASP.
>
>Al - traveling - off to COMMON Europe tomorrow
>
>Al Barsa, Jr.
>Barsa Consulting Group, LLC
>
>400>390
>
>914-251-1234
>914-251-9406 fax
>
>http://www.barsaconsulting.com
>http://www.taatool.com
>
>
>
>
>
>
>                     "Phil"
>                     <sublime78ska@yahoo        To:
><MIDRANGE-L@midrange.com>
>                     .com>                      cc:
>                     Sent by:                   Subject:     journalling
>overhead
>                     owner-midrange-l@mi
>                     drange.com
>
>
>                     06/06/01 12:35 AM
>                     Please respond to
>                     MIDRANGE-L
>
>
>
>
>
>
>I have been hearing for a few years now that journaling no longer causes a
>performance problem.  And I've been journaling files as I use embedded sql.
>
>I have been getting performance complaints lately on one particular
>program.
>The program is an interactive program that returns a rate.  It was written
>about 15 years ago.  It must read through a file which has about 200,000
>records in it and is recently journaled.
>
>My question is - can it be the journaling?
>
>Phil
>
>
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****************************************************************
Kevin M Howcroft                http://www.kmtcinc.net
AS/400 Technical Consultant     Voice:407.830.5960
kevinh@kmtcinc.net              Fax: 407.650.2638

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