That paints a much clearer picture!

Your current disks are the same size, PHYSICALLY, but they report different size because they have RAID striping on them. Back in the "AS/400" days we had SCSI disks which brought clear rules on RAID set building. With IBM i on POWER and SAS drives the RAID sets stripe across all disks so the size of the disks varies slightly.

So in this case you need to start RAID on the disks which will lower their apparent size to perhaps 127GB.

The rule you were referring to about different size disks has to do with Large differences in size. If you had a set of 70GB disks and a set of 140GB Disks you can clearly imagine that the 140 GB disks would end up twice as busy as they have twice the capacity and will naturally have twice as much of your stuff on them. This is generally the accepted limit for size difference, stated as "The largest disk should not be more than double the size of the smallest disk." Thus 35 GB disks should not be in the same ASP as 140GB disks.

Your disks are the same physical size and will at most only be slightly different in size so you are good there.

Once the new drives are RAIDed you'll add AND BALANCE them to the ASP. The system will them move (in your case) 1/2 of your current data to the new drives before it allows NEW data to be written to those new disks. This is because you are doubling the number of disks and disk capacity. Once that move is complete the disks will be become an active part of the ASP and life will be good!

Note that in your case if you 'oops' and do not select "And Balance" when you add the disks you likely would cause little or no pain. This is because you're adding so many disks that they can handle the new data. If you were adding just 2 or 4 drives to the 24 existing drives that would be a big difference.

- Larry "DrFranken" Bolhuis

On 12/15/2013 6:19 PM, BJ Vail wrote:
*This message was transferred with a trial version of CommuniGate(r) Pro*
A little more info. The current storage size is 2,997.5 GB. Capacity on the existing disks is 124.9 GB each, additional disks are 136.3 GB each (reported from iSeries Navigator).

From: BJ Vail <bjvail@xxxxxxxxxxxxx>
To: midrange-l@xxxxxxxxxxxx
Sent: Sunday, December 15, 2013 4:37 PM
Subject: Re: Adding additional storage to ASP

I used the AS/400 term loosely. It's a Power 720 system. I currently have 24 126.9 GB drives protected with raid 5 and am needing add an additional 24 139 GB drives with the other drawer I mentioned earlier.

Thanks for the response!

On Sun, Dec 15, 2013 3:58 PM CST DrFranken wrote:

Sir you are magical!! You are the only one on the planet that has SAS
disks connected to such an old machine!

As to the breaking of the ASP that's unlikely but there are some things
that you are clearly aware of with your comments. However:

You didn't say how big the current disks are or the quantity of them.
You also didn't say how big the new disks are or how many of them are
being added to the system ASP.
We also don't know the total capacity of your current storage, how full
it is, or if it's RAID or Mirror protected or (shudder) not protected at

Without that the best advice is to assure the new disk units are
protected when adding them to the ASP and be CERTAIN to use the "ADD AND
BALANCE" option when you do that. Failure to select "AND BALANCE" has
been known to bring systems completely to their knees. This is in
extreme situations but avoiding such problems is your best defense.

Better advice is possible with additional information.

- Larry "DrFranken" Bolhuis

On 12/15/2013 1:21 PM, BJ Vail wrote:

I recently added an additional disk storage unit to my AS/400. It's IBM Feature Code 5887, IBM EXP24S SFF Gen2 I/O Drawer. These disks are supposed to be added to the system and I'm a little unsure about how to do this.

I'm worried that I'll break the system if I add the additional 24 disks to the System ASP. The new disks are a larger size than the existing ones. I'm looking for a little insight about getting these disks added and usable by the system.

Thanks in advance,


This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives

This thread ...


Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2019 by and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].