Disk configuration on i OS PowerSystem

[Former Member]

Greetings,

I am an IBM BP responsible for PowerSystem i OS HW configuration. I received a query from the implem partner of my customer re: disk configuration for certain files for SAP. He refer to the following files: for Data Table they require RAID5 and for Online Data File, Offline Log File and Temp File it will require RAID1 disk configuration.

For customers already running SAP on i OS, how did you handle the disk configuration of these files (Data Table, Online Data File, Offline Log File and Temp File) or how was it configured? I have been working on System i configuration for sometime and have never seen a RAID1 disk configuration (except for the load source when RAID5 was not yet supported) due to its reliability and aside from the fact it will be very expensive.

Thanks.

[Former Member · Accepted solution]

Hi,

Yes u are correct. There is one library for the sapdata that will be in ASP1 and sap journals will be in asp2. ASP1 will be in raid5 and ASp2 is mirrored that what SAP is recommending. I think the customer is from MSSQL background.

Regards

Shylu

[Former Member · Accepted solution]

thanks for your reply Shylu.

From my limited understanding of the iSeries storage management, multiple ASPs can be created by using a pool of internal disks with RAID5 or RAID1 protection. Having both protection however will require additional HW resources like disk controller and possibly expansion drawer which may not be necessary with RAID5.

[Former Member]

If there already is a disk controller card with 1.5GB write cache + 1.6 GB read cahce (571E, 571F, 572F, etc.) with at least 6 units of 15,000 RPM disk units (4327,4328, 3766, etc.) in the system, you can just configure ASP 1 for all the disk units and use RAID-5 for all data of SAP and it would be fine in terms of system performance. Several of my local customers use this disk config and do fine for SAP ERP with 50-150 users. No need to store journal receivers in a separate ASP if you have this powerful disk controller card which has been available for iSeries for 5 years or so now,

[christian_bartels]

Hi,

for a general discussion of the correct setup for auxiliary storage pools (ASPs), please have a look at SAP Note 654801. Using a separate ASP for journal receivers is recommended in order to allow data recovery in case of disk failures that destroy the complete ASP despite of RAID protection. If you are using data replication software for high availability, it may not be necessary to configure a separate ASP for journal receivers, also if you don't care too much about data recovery (e.g. for a test or sandbox system).

When configuring a separate ASP for journal receivers, it is important to have enough disk arms to avoid queing (performance) problems. 3 disk arms should be the minimum configured. Usually you don't need that much space for receivers, so RAID-1 protection may be appropriate. If you want to configure more than 4 units and need the space, you can very well configure RAID-5 protection for the journal receiver ASP. The ASPs for the database library and the journal receivers must be configured for different RAID sets, otherwise you loose the recovery option after the loss of one RAID set.

Kind regards,

Christian Bartels.

[Former Member]

Christian, thank you for the detailed info above.