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Re: Setting kernel params after Mem and CPU upgrade?

 
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Steve Lewis
Honored Contributor

Re: Setting kernel params after Mem and CPU upgrade?

When performance tuning it is always necessary to consider the whole system.
You added CPU and memory, but did you also tune the database and storage to go with it?
You appear to have a bottleneck on one disk.

As a general point, a batch process such as a data load will consume all the resource allocated, sometimes to the detriment of another part of the system.
Increasing the processing power may have incidentally caused an overload of your database writers, causing head thrashing and huge queues to build up on the disk.

Re: Setting kernel params after Mem and CPU upgrade?

Kalin,

I'm assuming that c2t0d0 and c2t1d0 are youre mirrored boot disks. They don't seem to be so busy.

What is c4t0d0 ? is is a LUN on a SAN or is it a local disk? What do you have on this disk? presumably a filesystem (pvdisplay -v /dev/dsk/c4t0d0 should show us what logical volumes if any you have on this disk).

None of these figures look particularly alarming though, so maybe we're chasing the wrong thing here. How does the SAP load work? i.e. where does it load from and to in terms of disks/filesystems?)

HTH

Duncan

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Steven E. Protter
Exalted Contributor

Re: Setting kernel params after Mem and CPU upgrade?

dbc_min_pct 5 Default Immed
dbc_max_pct 5 5 Immed

I found setting max to 7 works 11.11.

Bill Hassell has seen some evidence of buffer cache at higher levels helping Oracle performance on cooked filesystems and HP-UX 11.23

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Kalin Evtimov
Regular Advisor

Re: Setting kernel params after Mem and CPU upgrade?

Hi Duncan,

you are right, c2t0d0 and c2t1d0 is the mirrored boot device and c4t0d0 is a disk array with a bunch of harddrives connected through fiber-channel cards (SAN).
The output is in the atached file.
In this case the SAP-System is reading and writing data from the SAN to the SAN, there is stored the whole data, since the DB is there. Therefore the great disk usage.

Re: Setting kernel params after Mem and CPU upgrade?

ok, next questions:

1) Do you have 2 or more paths to this disk or just one? Does your server just have the one FC card init it?

2) what type of disk array is it? Do you know how many and what type of disks actually provide the LUN? The thing is that in sequential IOs which we usually see during loads, reading and writing to the same disk(s) can be an issue, even if there is a disk array with cache involved.

3) If you only have one LUN, you should probably look at a fairly high scsi queue depth (number of IOs that can be sent concurrently to the disk array). Check its current value using:

scsictl -m queue_depth /dev/rdsk/c4t0d0

if its set to the default of 8 you can probably increase it - the maximum value will depend on your disk array, so consult with your SAN admin or array vendor.


Of course all of this assumes that the problem is with IO, which we can't really be sure of yet. You said you looked at sar outputs both before and after the memory and CPU were added. What did you see?

HTH

Duncan

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Kalin Evtimov
Regular Advisor

Re: Setting kernel params after Mem and CPU upgrade?

There is only one path.
Server has two cards.
Disk Array is MSA30 14x73Gb 15k rpm
queue depth is 8.

Unfortunately I don't have any I/O-data before the upgrade. I have only load and memory, but not disk. Both load and memory usage decreased after upgrade..
Thank you for your support.

Re: Setting kernel params after Mem and CPU upgrade?

OK, so the MSA30 is a SCSI JBOD disk tray - you must have some sort of disk array controller in front of that - either MSA1000 or MSA1500 if you really are attached by fibre, otherwise if you are attached via SCSI you might have an internal SmartArray controller.

What does

diskinfo /dev/rdsk/c4t0d0

state?

HTH

Duncan

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Kalin Evtimov
Regular Advisor

Re: Setting kernel params after Mem and CPU upgrade?

SCSI describe of /dev/rdsk/c4t0d0:
vendor: HP
product id: LOGICAL VOLUME
type: direct access
size: 284503117 Kbytes
bytes per sector: 512

:(
Kalin Evtimov
Regular Advisor

Re: Setting kernel params after Mem and CPU upgrade?

The guy that manages the machine told me that it is connected via SCSI-Kabel, it is still not attached to the SAN

Re: Setting kernel params after Mem and CPU upgrade?

Kalin,

so you have a SmartArray card in your system. We should be able to interrogate that to determine the configuration of your storage:

ioscan -kfnd ciss

Should find us the device file for the SmartArray controller.

saconfig /dev/cissX

replacing cissX with what you get back from the ioscan, should show us how the LUN is presented to the host.

HTH

Duncan

I am an HPE Employee
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