Re: Sudden Backup Slowdown

From: Jeffrey Beckstrom <jbeckstrom_at_gcrta.org>
Date: Tue, 05 Nov 2019 10:02:38 -0500
Message-Id: <5DC18F0E0200000B0006496E_at_groupwise2014.gcrta.org>

What does your internet traffic look like during this time period since you are going to the Cloud?
>>> "Charlotte Hammond" (Redacted sender"charlottejanehammond" for DMARC) <dmarc-noreply_at_freelists.org> 11/5/19 9:48 AM >>> Hi Mladen,

These are SBT channels using Oracle Secure Backup Cloud Module
(OSBWS).
No backup suite is being used - these are simply command line RMAN jobs run from a scheduler.

I'll have a look at profiling the CPU usage a bit more and see where that takes me. Unfortunately, as mentioned, I do not have a baseline available for the "good" backups.

Thanks,
Charlotte

On Tuesday, November 5, 2019, 12:14:19 PM GMT, Mladen Gogala <gogala.mladen_at_gmail.com> wrote:

Hi Charlotte!
What kind of a channel do you allocate, disk or SBT? If SBT, what kind of backup suite are you using? Stuff like NetBackup, Commvault or TSM is highly complex and dependent on may factors. Regards
On 11/5/19 3:27 AM, Charlotte Hammond (Redacted sender charlottejanehammond for DMARC) wrote:

Hi Nenad,

The average run queue is about 20 (peaking at about 25) whilst the backup is running. The figure is the same for both the slow and fast runs. I've graphed them out and they look pretty much the same. This is a fairly high figure but it doesn't seem to have changed.

We have 16 backup channels and 16 CPUs (2 threads per processor).

Yes, the compression is "basic" but that has not changed.

Thanks,
Charlotte

On Monday, November 4, 2019, 09:26:33 PM GMT, Noveljic Nenad <nenad.noveljic_at_vontobel.com>
( mailto:nenad.noveljic_at_vontobel.com) wrote:

Hi Charlotte,

Run queue length of 20-25 means the number of processes competing for CPU. How many CPUs do you have? How many RMAN channels are configured?

What was the average length of run queues during a good run?

With regard to backup compression, basic will use significantly more CPU than the others, but as you mentioned that the backup size is the same, the backup algorithm probably hasn‘t changed.

I‘d therefore suggest first clarifying the CPU load on the server.

Best regards,

Nenad

Von: Charlotte Hammond <charlottejanehammond_at_yahoo.com> Datum Montag, 04. Nov. 2019, 6:15 PM
An: dmarc-noreply_at_freelists.org <dmarc-noreply_at_freelists.org>, ORACLE-L <oracle-l_at_freelists.org>, Noveljic Nenad <nenad.noveljic_at_vontobel.com> Betreff: Re: Sudden Backup Slowdown

Hi Nenad,

The only real difference between the AWR reports is that the statistic "RMAN cpu time (backup/restore)" is about 50% longer than before. Sar shows the run queues as 0 (or close to 0) before and after the backup in both cases and similar during the backup (about 20-25).

Thanks,
Charlotte
On Monday, November 4, 2019, 02:51:38 PM GMT, Noveljic Nenad <nenad.noveljic_at_vontobel.com>
( mailto:nenad.noveljic_at_vontobel.com) wrote:

If there weren’t any idle CPUs during backup, I’d first verify the statement “The server itself has no other activity during the backup window.” by measuring the length of the run queues. In other words, to confirm there aren’t any other processes competing for CPUs.

What differences do you see in AWR reports?

Best regards,

Nenad

https://nenadnoveljic.com/blog/

From: oracle-l-bounce_at_freelists.org<oracle-l-bounce_at_freelists.org>
( mailto:oracle-l-bounce_at_freelists.org) On Behalf Of Charlotte
Hammond
Sent: Montag, 4. November 2019 15:22
To: ORACLE-L <oracle-l_at_freelists.org>
( mailto:oracle-l_at_freelists.org)

Subject: Sudden Backup Slowdown

Hello All,

I'm trying to explain why my level 0 rman backups have suddenly jumped from 8hours to 12 hours. The size of the backup has barely changed and there has been no configuration changes. AWR and O/S statistics show that CPU for all the channels are maxed out at ~99% (presumably backup compression) for most of this time, both in the 8 hour case and 12 hour case. The server itself has no other activity during the backup window.

This is on 11.2.0.4 on AWS EC2 backing up to S3 storage.

I'm not looking for tuning advise here (thanks though!) - I'm really hoping for some advise on finding an explanation for the change in times. Given that all it's doing is sitting on CPU I'm not sure what else I can investigate - especially with limited ability to cross-reference it with the "good old" runs. It's been 8 hours for months and months, and has now been 12 hours for the last 3 weeks. There was no gradual increase - just a step change.

Thanks!
Charlotte

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Received on Tue Nov 05 2019 - 16:02:38 CET

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