SAP on third ASP (high speed controller optimize)

[mariaeugenia_amoros]

We are installing SAP on i5 Model 550 16GB Power 5+. Its storage configuration is as follows:

- 4 15k 35GB disk in the CPU module (with a normal disk controller).

- 1 disk expansion box with 8 15k 35GB (with high speed controller).

- 1 disk expansion box with 8 15k 35GB (with high speed controller).

We configured 3 ASP.

ASP1 (2 disks on the CPU module in mirroring mode).

ASP2 for journal receivers (2 disks on the CPU module in mirroring mode).

ASP3 for SAP (16 disks in RAID5 and 2 parity groups, one per each controller).

We told our consultant about installing SAP on ASP3 because every disk access would be done through high speed controllers. If we create ASP1 with two disks from the CPU module (slower controller) and sixteen disks from the expansion boxes (high speed controllers) we think disk access will not be optimal because slower controller will penalize faster controllers.

Our consultant says that SAP recommends ASP1 for OS & SAP and ASP2 for journal receivers.

I think SAP recommends not using the same ASP for SAP and journal receivers, but nothing about having SAP and OS in the same ASP necessarily.

IBM doesn't say anything about. They have a big red book and it says exactly what SAP says.

We want to install SAP on ASP3 because having 16 disks with two high speed controllers for SAP seems to be more optimal than having ASP1 mixing disk on the CPU slower controller and on the high speed controllers.

Any comments or recommendations?

[Former Member · Accepted solution]

Are your disk expansion units feature 0595 ? - these can take 12 disks each. In that case I would agree with Satid, and put the 4 disks currently allocated to the system unit (CEC) of the i550 into the 0595s - i.e. 10 disks in each instead of 8.

I'm assuming this server was ordered with auxiliary write cache cards for the 2780 (or 2757) disk controllers, as that is a recommendation (enforced) now for RAID5. (these show up as 5580 (or 5581) on the shipping documents). They are described in the redpaper:

http://www.redbooks.ibm.com/abstracts/redp4003.html?Open

Michael.

[Former Member · Accepted solution]

>>>>

put the 4 disks currently allocated to the system unit (CEC) of the i550 into the 0595s - i.e. 10 disks in each instead of 8.

<<<<

Mr. Power

I agree that your suggestion is indeed a better idea for best possible disk access performance. But this can be done only if the customer has HMC (Hardware Management Console) with the machine to help specify that the Load Source Unit disk is in 5095/5094 tower. Without HMC, I'm afraid the machine will always looks for LSU disk in the CPU tower as its default location.

Satid S.

IBM Thailand

[mariaeugenia_amoros · Accepted solution]

Thank you very much for all your answers. They have helped me so much.

Thanks to Satid and M. Power I have deeply studied our system. I am new on these machines and it is an exciting (but expensive) world.

The CEC have a 5727 RAID Enabler Card which replace imbedded SCSI controller (570B I guess).

The “expansion boxes” are two 0595. Each one has a 5580 controller (2780 SCSI controller + 5708 Aux. write Cache).

You were right. I am sorry. I could have studied it before to help you in your answers. But all of you guys are very competent and have guessed which components are in my system.

Just one more question I couldn’t answer reading lots of documents and web pages from IBM. I think that is not possible to have Load Source Disk on 0595 if you don’t have logical partitions. Is that right? By default LSD need to be in SCSI controller which is in 9406-550 CEC.

[Former Member · Accepted solution]

Hi Jose,

I think you are more or less right with the load source.

I would like to stress, that there will be no performance penalty to put the journal receivers into ASP1 - it is "just" the safety for backup & recovery.

I configure it at most of the (smaller) clients with ASP1 only.

Regards

Volker Gueldenpfennig, consolut.gmbh

http://www.consolut.de - http://www.4soi.de - http://www.easymarketplace.de

[mariaeugenia_amoros · Accepted solution]

Thank you very much.

We will install SAP and Journal on ASP1. We can do test with journal in ASP2 at any time if we think we could have problems with security.

One more question (last one &#61514;). If I configure RAID5 and I have three parity groups, could I loose one disk per parity group without loosing data?

As consultant had started SAP installation and stopped it when we were thinking about ASPs, now he asks us to reinstall OS400. I think it is not necessary but I will do. It will be my first OS400 install... It's exciting! Isn't it?

[Former Member · Accepted solution]

Hi Jose,

I'm sorry, but I would not reinstall OS/400, but I would "reinstall" the basis consultant ! Obviously he is not that keen on OS/400 if he "needs" a new OS copy beacuse of his first installation test :-((

yes, you are correct, you can lose 1 disk in each raid-set - as soon as you lose 2 disks in 1 raid set the complete ASP1 is dead ...

Regards

Volker Gueldenpfennig, consolut.gmbh

http://www.consolut.de - http://www.4soi.de - http://www.easymarketplace.de

[mariaeugenia_amoros]

Thank you very much Volker. Your post has helped me to pay more attention to temp-storage. That one is a good reason not to do what I was doing.

Since I wrote to this forum, nobody has focused as you on that topic. That is the key to change our thoughts.

ASP1 need to be much bigger (more arms) and to do that we need to add disks from the 0595 to ASP1.

I am considering not using ASP2. I would make a single ASP. With my hardware it is not possible to have mirroring and RAID5 on the same controllers so I should have 4 disks in RAID5 for ASP2 to store Journal Receivers… Is that necessary? I think I could be important for security reasons only.

I could create ASP2 at anytime and compare performance. In ASP1 journal receivers would have 16 arms (less 2 because RAID5). We have two parity groups.

[Former Member]

I agree with Volker that your ASP design has a flaw. ASP1 with only just 35GB space will cause U trouble because of the simple fact that SAP can possibly need up to almost 100GB disk space for its temporary work area. And this temp disk space can only exist in ASP 1. Whne ASP 1 is full, your system will IPL.

Can U be more specific as to what feature your "high speed controllers" are? If they are FC#2757 or 2780 or 5580 (which are the current best-performing disk controllers for System i), then I recommend that U create only ONE ASP with ALL the disk units U have in the box with 3 RAID-5 sets. The 5727 base disk controller in the CPU tower will NOT penalize your overall disk access performance in a substantial manner if your other 2 disk controllers are one of the best-performing controllers that I indicate. This is due to round-robin nature of disk allocation algorithm of i5/OS that will spread more data onto those disk units in the expansion towers than the 4 units in system tower.

And with the high performance disk controllers being used and more than 10 disk units in ASP 1, there is no need to separate journal receiver library into a different ASP from SAP database library. Having only one ASP also helps simplify your disk management.

There is a Technote paper that explains this at : http://www.redbooks.ibm.com/Redbooks.nsf/portals/systemiTips and select to read the article named "Journaling - User ASPs Versus the System ASP".

So, please check if you are using 2757 or 2780 or 5580 or not. If so, U have the best performing disk controller that can help you simplify disk management by using only one ASP. If not, let me know what feature they are and I can provide further suggestion.

Satid S.

IBM Thailand

[Former Member]

Hello José,

SAP recommends ASP1 and ASP2 just for seperating database and jounalreceivers. There are two reasons for this:

1. Performance ( but with new powerful or cacheful controllers it is only in rare cases important)

2. Security, if you loose one ASP, you still have the other for complete recovery.

SAP on i5 is not like other platforms. We do not split SAP, DB, Log, Temp, Swap and OS. We just need to configure 1 or 2 ASPs, that is a real benefit.

You should think about security, if you need the additional ASP.

Depending on usage of the SAP-system, performance should not become relevant. (But can be (re-)configured later)

The question is, for which Solution was the hardware sized? Sizing and implementation should harmonize.

Regards

Guido

[Former Member]

Hi Jose,

first of all, you can install SAP in ASP3 - that is no problem at all. SAP recommends to not run database and journals in one ASP. That is what you want to do.

But, you should not go for that because of other reasons. Your ASP 1 will ONLY have 2 disks and therefore the temp-storage will run on 2 disks only => your performance will be very bad on these 2 disks.

=> I would put 2-4 disks into ASP2 for journals and all the other disks into ASP1 - even with the slower controllers.

To run only 2 slow disks ASP 1 will kill your server :-(((

If you do have more questions, let me know ...

Regards

Volker Gueldenpfennig, consolut.gmbh

http://www.consolut.de - http://www.4soi.de - http://www.easymarketplace.de