2104-DU3 RAID 5 on pSeries 610 model 6C1

[beumii00]

What is exactly required to have RAID5 implemented on 2104-DU3 combined on a
pSeries 610 model 6C1 ?

 

[aixmurderer]

Ditto here, I cannot find any info anywhere. What I have figured out is that it is seemingly software RAID5 as opposed to a hardware RAID solution.

IBM recommended 4 drives at purchase time, 1 for the OS and 3 for the RAID5 of everything else like DB2. Why? Why not RAID5 everything onto 3 drives?

If I had to go for the 3 disk option, should I install the OS to all three disks at install time or only to hdisk0? Is there support for RAID5 setup in smitty?

Sorry about all the questions, my exposure up to now has been to older equipment (220's, 250's and 43P's) and hardware RAID solutions only. IBM Certified Specialist - MQSeries
IBM Certified Specialist - AIX 5 pSeries System Administration

 

[bjverzal]

You'll need a SCSI RAID adapter. For example a feature code 2498.

As for the 4-drive (1 for OS, 3 for everything else), this is not possible with RAID 5, as data will be striped across all drives in the array. Perhaps, one will be a hot spare and 3 will be for data.

3 drives are a minimum requirement for a RAID-5 array. 2 drives for a RAID-1 array (mirroring).

Bill.

 

[beumii00]

Thanks Bill for the info.

We have already ordered a SCSI RAID Adapter with the feature code you mentioned.
And as i have understood from some readings, there are
smit entries regarding defining RAID Arrays and disks.

Francois.

 

[aixmurderer]

It seems the SCSI card supplied to us is not the RAID type, so much for that then after specifying that RAID5 is a requirement.

What I have done in the end is do a triple mirror of rootvg over 3 disks, and kept the one drive as a hot spare. Modified the bootlist to list all three disks, so in effect we should be pretty safe.

The down side is no disk striping, so disk I/O could become an issue later on. That was exactly our present 43P's problem, max 128M RAM, so a lot of disk paging as RAM was overbooked by 60M. New server has 2Gb RAM, so hopefully that problem won't surface in a hurry. IBM Certified Specialist - MQSeries
IBM Certified Specialist - AIX 5 pSeries System Administration

 

[mjurado]

Note:
AIX can not boot from RAID adapters, that´s the reason AIX machines have to have disks whithout hardware RAID. The only protection you can have for rootvg is mirroring made by the AIX itself, not from the adapter.

 

[kaboo]

Hi, I'm interested to know whether a 2104-DU3, run under AIX 4.3, supports two different RAID type ? E.g. RAID 0 on some disk; while RAID 5 on some other ? What hardware or s/w requirements are there ? Thanks a lot.

 

[fluffybunny]

AIX only has support for software RAID0. For other RAID levels, you will need a RAID adapter as mjurado has mentioned.
The RAID adapter (#2498) PCI 4-Channel Ultra3 SCSI RAID Adapter has support for RAID levels 0, 1, 1E, 5 and 5E.
This adapter is not bootable. If you want to install the 2104-DU3 with hardware RAID 0, 1, 1E, 5 and 5E, the you will have to connect the DU3 to this RAID adapter. You cannot install AIX on the DU3 when running on this adapter. You will need a minimum of one disk sitting in the 610 for installation of AIX. If you want to mirror the OS, then you can use AIX mirror to perform this, which requires two disks installed in the server. AIX has support for up to three way mirror but I rather think that this is a waste of HDD space.

As for different RAID levels on the disks in the DU3 subsystem, yes you can have different RAID levels. You will have to specify different RAID groups and allocate the disks to these groups.

If I am not mistaken, this adapter requires some APARs for AIX 4.3.3. Check under IBM support for updates.

Regards.