IBM POWER 720  8205-E6B

Posted on 2011-10-27
Last Modified: 2013-11-17
configuring a POWER 720 server. Loading AIX 6.1. Server has base RAID feature 8630 with all  drive slot filled. 8 total drives.

Wanting to mirror boot on hdisk0 and hdisk1.

first, once 2 physical drives are mirrored boot devices,  is it still a possibility to use other RAID sets within that pair.
also wondering about performance.
What is most efficient RAID and grouping ?  
base feature 8630 offers RAID's 0,5,6,and 10.
Is pairing the best choice for efficiency ?
What happens with the first pair of mirrored boot drives as far as options to include them into one big RAID set with all the drives included if that is the best case ?


Question by:RNH4
    LVL 12

    Accepted Solution

    The best peformance is 0, or striping, but has no fault tolerance. With 1, you are writing the data twice. Very fault tolerant but bad performance. RAID 10 puts a substantial load on your RAID controller, regardless of how you actually configure your 10 array, which is an array of an array.

    The best performance with fault tolerance is RAID 5 with a minimum of 4 disks. 3 is all that is required to make RAID5 , but the performance boost after adding the 4th disk is noteable.

    Not sure what you mean about trying to RAID in your boot mirror on another array? I think you can break the space time continuum if you do that.
    LVL 20

    Assisted Solution

    It is definitely best to configure the two physical disks for the boot disk and miiror, as system disks. This will make your life simpler in the event of a failure, as you can easily replace the primary with the mirror in the event of failure.

    The remaining six disks can be formatted for the RAID array by first making them array candidates, and then configuring the array. I agree that RAID 5 is your best choice. You could create two 3 disk RAID 5 arrays, or one with all the disks. Since you effectively loose one disk in each array you configure, using all in one array would be your best choice. For the best integrity I would put 5 of the 6 disks in one RAID 5 array, and then configure the sixth as a hot spare.

    If you do not need all disks (space) in your array to start with, I would leave one of them unconfigured, put four in the RAID 5, and make one a hot spare.

    Author Closing Comment

    based on customer request a RAID 10 array was created with the remaining 6 drives. The first drive ( hdisk0 ) had O.S. , hdisk1 was the mirror.

    Thanks !

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