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* Linux VM Sizing
@ 2025-07-28 23:41 Sam Stearns <sam.stearns@dat.com>
2025-07-28 23:52 ` Re: Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
2025-07-29 01:03 ` Re: Linux VM Sizing Ron Johnson <ronljohnsonjr@gmail.com>
2025-07-29 02:14 ` Re: Linux VM Sizing Rui DeSousa <rui.desousa@icloud.com>
2025-07-29 06:30 ` Re: Linux VM Sizing Laurenz Albe <laurenz.albe@cybertec.at>
0 siblings, 4 replies; 7+ messages in thread
From: Sam Stearns @ 2025-07-28 23:41 UTC (permalink / raw)
To: Pgsql-admin <pgsql-admin@lists.postgresql.org>; +Cc: Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
Howdy,
We are sizing a Linux VM to migrate our Oracle production database to. We
are currently running on an Oracle Database Appliance. Oracle CPU / memory
usage stats are:
CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
Memory % usage - 100% usage of 600G SGA
Based on the above can anyone give advice as to how to size the CPU /
memory of the Linux VM, please?
Thanks,
Sam
--
Samuel Stearns
Team Lead - Database
c: 971 762 6879 | o: 971 762 6879 | DAT.com
<https://www.dat.com/?utm_medium=email&utm_source=DAT_email_signature_link;
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
@ 2025-07-28 23:52 ` Sam Stearns <sam.stearns@dat.com>
3 siblings, 0 replies; 7+ messages in thread
From: Sam Stearns @ 2025-07-28 23:52 UTC (permalink / raw)
To: Pgsql-admin <pgsql-admin@lists.postgresql.org>; +Cc: Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
I should clarify that we are converting to Postgres.
On Mon, Jul 28, 2025 at 4:41 PM Sam Stearns <sam.stearns@dat.com> wrote:
> Howdy,
>
> We are sizing a Linux VM to migrate our Oracle production database to. We
> are currently running on an Oracle Database Appliance. Oracle CPU / memory
> usage stats are:
>
> CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
> Memory % usage - 100% usage of 600G SGA
>
> Based on the above can anyone give advice as to how to size the CPU /
> memory of the Linux VM, please?
>
> Thanks,
>
> Sam
>
> --
>
> Samuel Stearns
> Team Lead - Database
> c: 971 762 6879 | o: 971 762 6879 | DAT.com
>
> <https://www.dat.com/?utm_medium=email&utm_source=DAT_email_signature_link;
>
>
--
Samuel Stearns
Team Lead - Database
c: 971 762 6879 | o: 971 762 6879 | DAT.com
<https://www.dat.com/?utm_medium=email&utm_source=DAT_email_signature_link;
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
@ 2025-07-29 01:03 ` Ron Johnson <ronljohnsonjr@gmail.com>
3 siblings, 0 replies; 7+ messages in thread
From: Ron Johnson @ 2025-07-29 01:03 UTC (permalink / raw)
To: pgsql-admin
On Mon, Jul 28, 2025 at 7:42 PM Sam Stearns <sam.stearns@dat.com> wrote:
> Howdy,
>
> We are sizing a Linux VM to migrate our Oracle production database to. We
> are currently running on an Oracle Database Appliance. Oracle CPU / memory
> usage stats are:
>
> CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
> Memory % usage - 100% usage of 600G SGA
>
Linux uses all available cache; is Oracle different? (IOW, would it also
use 100% of 800GB?)
> Based on the above can anyone give advice as to how to size the CPU /
> memory of the Linux VM, please?
>
Our 8TB Oracle DB was 6TB when migrated to PG 12 (this was a while ago)
and the AWS RDS Postgresql instance (which was spec'd -- before I got to
the project -- the same as the on-prem Linux server since the Oracle server
ran 60-70%) was constantly less 10% of capacity in CPU and RAM.
--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
@ 2025-07-29 02:14 ` Rui DeSousa <rui.desousa@icloud.com>
3 siblings, 0 replies; 7+ messages in thread
From: Rui DeSousa @ 2025-07-29 02:14 UTC (permalink / raw)
To: Sam Stearns <sam.stearns@dat.com>; +Cc: Pgsql-admin <pgsql-admin@lists.postgresql.org>; Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
> On Jul 28, 2025, at 7:41 PM, Sam Stearns <sam.stearns@dat.com> wrote:
>
> Howdy,
>
> We are sizing a Linux VM to migrate our Oracle production database to. We are currently running on an Oracle Database Appliance. Oracle CPU / memory usage stats are:
>
> CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
> Memory % usage - 100% usage of 600G SGA
>
> Based on the above can anyone give advice as to how to size the CPU / memory of the Linux VM, please?
>
It really depends on your application. For an Oracle to Postgres migration we estimated Postgres at 80% of Oracle and purchased larger system based on that metric.
We still had some initial performance issues. Oracle is very forgiving of bad code.
Here’s is some of the issues that I ran into that had to be address. The project was circa was with Postgres 9.6.
1. Rewriting of poorly written views; i.e. view nested on top of other views all access the same table underlying tables, etc
2. Hints —Rewriting some queries to influence the planner to choose better execution plan (i.e. leading table, etc). Postgres does not have hints.
4. Some queries needed to be rewritten to make use of fencing; i.e. using materialized CTE to improve performance.
5. Exception handling - exception handling makes use of xid’s; thus our transaction ids wrap arounds where occurring every other month.
We slowly replaced the exception handling code as a lot of was not needed with Postgres; reducing our transaction wrap around to just over a year.
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
@ 2025-07-29 06:30 ` Laurenz Albe <laurenz.albe@cybertec.at>
2025-07-29 07:14 ` Re: Linux VM Sizing Deepak Goel <deicool@gmail.com>
3 siblings, 1 reply; 7+ messages in thread
From: Laurenz Albe @ 2025-07-29 06:30 UTC (permalink / raw)
To: Sam Stearns <sam.stearns@dat.com>; Pgsql-admin <pgsql-admin@lists.postgresql.org>; +Cc: Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
On Mon, 2025-07-28 at 16:41 -0700, Sam Stearns wrote:
> We are sizing a Linux VM to migrate our Oracle production database to. We are
> currently running on an Oracle Database Appliance. Oracle CPU / memory usage stats are:
>
> CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
> Memory % usage - 100% usage of 600G SGA
>
> Based on the above can anyone give advice as to how to size the CPU / memory of the Linux VM, please?
Choose something that is about as strong as the old hardware.
If you find that the old machine is too strong for the current
Oracle workload, you can also downsize.
Yours,
Laurenz Albe
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
2025-07-29 06:30 ` Re: Linux VM Sizing Laurenz Albe <laurenz.albe@cybertec.at>
@ 2025-07-29 07:14 ` Deepak Goel <deicool@gmail.com>
2025-07-29 15:00 ` Re: Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
0 siblings, 1 reply; 7+ messages in thread
From: Deepak Goel @ 2025-07-29 07:14 UTC (permalink / raw)
To: Laurenz Albe <laurenz.albe@cybertec.at>; +Cc: Sam Stearns <sam.stearns@dat.com>; Pgsql-admin <pgsql-admin@lists.postgresql.org>; Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
CPU, you are good.
Memory, bump it up by 2
Deepak
"The greatness of a nation can be judged by the way its animals are treated
- Mahatma Gandhi"
+91 73500 12833
deicool@gmail.com
LinkedIn: www.linkedin.com/in/deicool
"Plant a Tree, Go Green"
Make In India : http://www.makeinindia.com/home
On Tue, Jul 29, 2025 at 12:01 PM Laurenz Albe <laurenz.albe@cybertec.at>
wrote:
> On Mon, 2025-07-28 at 16:41 -0700, Sam Stearns wrote:
> > We are sizing a Linux VM to migrate our Oracle production database to.
> We are
> > currently running on an Oracle Database Appliance. Oracle CPU / memory
> usage stats are:
> >
> > CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314 processor)
> > Memory % usage - 100% usage of 600G SGA
> >
> > Based on the above can anyone give advice as to how to size the CPU /
> memory of the Linux VM, please?
>
> Choose something that is about as strong as the old hardware.
>
> If you find that the old machine is too strong for the current
> Oracle workload, you can also downsize.
>
> Yours,
> Laurenz Albe
>
>
>
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Linux VM Sizing
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
2025-07-29 06:30 ` Re: Linux VM Sizing Laurenz Albe <laurenz.albe@cybertec.at>
2025-07-29 07:14 ` Re: Linux VM Sizing Deepak Goel <deicool@gmail.com>
@ 2025-07-29 15:00 ` Sam Stearns <sam.stearns@dat.com>
0 siblings, 0 replies; 7+ messages in thread
From: Sam Stearns @ 2025-07-29 15:00 UTC (permalink / raw)
To: Deepak Goel <deicool@gmail.com>; +Cc: Laurenz Albe <laurenz.albe@cybertec.at>; Pgsql-admin <pgsql-admin@lists.postgresql.org>; Joseph Miller II <joseph.miller@dat.com>; Thierno Diallo <thierno.diallo@dat.com>; Peter Garza <peter.garza@dat.com>; Henry Ashu <henry.ashu@dat.com>
Thank you everyone for the advice so far!
Sam
On Tue, Jul 29, 2025 at 12:14 AM Deepak Goel <deicool@gmail.com> wrote:
> CPU, you are good. Memory, bump it up by 2 Deepak "The greatness of a
> nation can be judged by the way its animals are treated - Mahatma Gandhi"
> +91 73500 12833 deicool@ gmail. com LinkedIn: www. linkedin.
> com/in/deicool "Plant a Tree,
> ZjQcmQRYFpfptBannerStart
> This Message Is From an Untrusted Sender
> You have not previously corresponded with this sender.
>
> ZjQcmQRYFpfptBannerEnd
> CPU, you are good.
>
> Memory, bump it up by 2
>
>
> Deepak
> "The greatness of a nation can be judged by the way its animals are
> treated - Mahatma Gandhi"
>
> +91 73500 12833
> deicool@gmail.com
>
> LinkedIn: www.linkedin.com/in/deicool
>
> "Plant a Tree, Go Green"
>
> Make In India : http://www.makeinindia.com/home
>
>
> On Tue, Jul 29, 2025 at 12:01 PM Laurenz Albe <laurenz.albe@cybertec.at>
> wrote:
>
>> On Mon, 2025-07-28 at 16:41 -0700, Sam Stearns wrote:
>> > We are sizing a Linux VM to migrate our Oracle production database to.
>> We are
>> > currently running on an Oracle Database Appliance. Oracle CPU / memory
>> usage stats are:
>> >
>> > CPU % usage - 25% of 20 cores / 40 threads (Intel® Xeon® S4314
>> processor)
>> > Memory % usage - 100% usage of 600G SGA
>> >
>> > Based on the above can anyone give advice as to how to size the CPU /
>> memory of the Linux VM, please?
>>
>> Choose something that is about as strong as the old hardware.
>>
>> If you find that the old machine is too strong for the current
>> Oracle workload, you can also downsize.
>>
>> Yours,
>> Laurenz Albe
>>
>>
>>
--
Samuel Stearns
Team Lead - Database
c: 971 762 6879 | o: 971 762 6879 | DAT.com
<https://www.dat.com/?utm_medium=email&utm_source=DAT_email_signature_link;
^ permalink raw reply [nested|flat] 7+ messages in thread
end of thread, other threads:[~2025-07-29 15:00 UTC | newest]
Thread overview: 7+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2025-07-28 23:41 Linux VM Sizing Sam Stearns <sam.stearns@dat.com>
2025-07-28 23:52 ` Sam Stearns <sam.stearns@dat.com>
2025-07-29 01:03 ` Ron Johnson <ronljohnsonjr@gmail.com>
2025-07-29 02:14 ` Rui DeSousa <rui.desousa@icloud.com>
2025-07-29 06:30 ` Laurenz Albe <laurenz.albe@cybertec.at>
2025-07-29 07:14 ` Deepak Goel <deicool@gmail.com>
2025-07-29 15:00 ` Sam Stearns <sam.stearns@dat.com>
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