RE: SSD/HDD Performance & Balancing

Sue wrote:

As to why you ended up with 6 and 12, that is a good question and there are many
potential answers. One possibility is you started with 12 drives and later added
6 more hoping for better performance or needed that much more storage.

When we originally added some SSD's to our Power7 configuration, the controller cards we had could only access 8 SSD's in an enclosure allowing 24. When we asked the system to start RAID5 protection, it automatically set up 2 RAID sets of 4 drives each:

Parity Resource Hot Spare
Set ASP Unit Type Model Name Status Protection
2 57B5 001 DC04 RAID 5 N
33 4035 58B4 109 DMP127 Active
33 4034 58B4 109 DMP129 Active
33 4036 58B4 109 DMP121 Active
33 4033 58B4 109 DMP119 Active
3 57B5 001 DC04 RAID 5 N
33 4032 58B4 109 DMP123 Active
33 4031 58B4 109 DMP133 Active
33 4029 58B4 109 DMP125 Active
33 4030 58B4 109 DMP131 Active

When we upgraded our controller cards to ones that can now access all 24 slots of the disk enclosure and added 8 additional drives, only one RAID set of 8 was set up:

Parity Resource Hot Spare
Set ASP Unit Type Model Name Status Protection
1 57B5 001 DC04 RAID 5 N
33 4037 58B4 109 DMP146 Active
33 4040 58B4 109 DMP148 Active
33 4044 58B4 109 DMP150 Active
33 4039 58B4 109 DMP139 Active
33 4041 58B4 109 DMP147 Active
33 4038 58B4 109 DMP138 Active
33 4043 58B4 109 DMP140 Active
33 4042 58B4 109 DMP149 Active

The ODD thing though and I wish this wasn't so, I was never given a chance to define the RAID sets the way I wanted to. I use to always set up my RAID sets to align with my ASP's. Now, because the system won't let me define my own RAID sets, I have RAID sets that span multiple ASP's. Not a good idea from a protection point of view.

The resource names of a bunch of our devices were renamed too. I figured this had something to do with replacement of the controller cards.

I want to attempt to clean this up, but to reconfigure RAID and move drives between ASP's (especially iASP's which have to be offline to make any changes) is so time consuming that it is almost impossible to get enough down time to make it happen!

There has to be an easier way to change disk configurations on systems with over 10TB of storage... Maybe in the future (??)


Reply or Forwarded mail from: Kenneth E Graap

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Sue Baker
Sent: Thursday, February 26, 2015 5:58 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: SSD/HDD Performance & Balancing