Re: External disk for iSeries -- MIDRANGE-L

I'm clearly on the fence here, perhaps actually only one leg on the fence as I'm just not comfortable with my 'stuff' not being on absolutely reliable and trustworthy storage. Given that when OS/400's single level storage is missing so much as a single disk, it's vaporized entirely I don't want even some of my stuff on disks I don't have absolute confidence in. A big part of my job is system management, configuration, system migrations, LPAR and such work. When I do something with internal disk, it works. Not usually, not most of the time, it just works, period. I like that. It's predicable, I know what I can and can't do and about how long to expect it to take.

Others have mentioned the vast amounts of time they DON'T spend managing iSeries disk. This is value folks and it's what you buy when you buy iSeries. You also get performance. Performance that is nicely balanced on arms, controllers, and busses. We've been able to add controllers and disks for many releases while the system is running and with the i5 and V5R3 we can add towers to HSL loops so there is no reason to stop the system at all when storage needs increase.

Some say they desire to mirror their system to disks outside of the iSeries box. (i.e. one set of disks that are IBM and one set that are not) I just don't see this being a useful solution. You end up with differing performance, geometry, controller speed etc. Mirrored data cannot be considered written if it's not on both disks or at least in protected caches so this could make for some interesting performance or integrity implications. Remember that it's OS/400 that does mirroring, not the hardware as with RAID.

Some suggest use of external disks for some pieces of stuff. This s a place where I could get some traction. If you have a huge amount of data in the IFS that's not mission critical for example I think it does make sense for an external iASP to be created and mapped to an IFS directory. Now it becomes available to OS/400 but if it's gone, OS/400 just issues a complaint but doesn't go *POOF* because it's disks are still there. An iASP with perhaps test data or even historical data on external disk could be utilized, in each case these are things that don't shut down my business when they're missing for a day or two.

Is iSeries disk expensive? Yup, but it's getting better all the time, the new announcement helped us once again. But remember as always, you get what you pay for.

I know my experience with external and with NON-IBM internal disk and it SUCKED. Q: What goes Ka-CHUNK, Ka-CHUNK, Ka-CHUNK, Ka-CHUNK at 2 AM during a system migration? A: A full set of EMC disk units that suddenly decide they don't want to play any longer. This is NOT what you want your disks to do during a migration, or any other time for that matter!! One customer required TEN disks be shipped from their vendor to get a set of FOUR of them to come up! I can barely remember ANY non-IBM disks with a happy story. Put my stuff on those? No thanks!

So I have a leg on the fence because I see out there potential valuable uses for external disk but I'm not ready to commit the best OS on the planet to hardware that isn't.

- Larry


Jeff Bull wrote:

I've just read an article on external dasd for the iSeries and thought that you guys/gals might be interested......

-- Larry Bolhuis IBM eServer Certified Systems Expert: Vice President iSeries Technical Solutions V5R2 Arbor Solutions, Inc. iSeries LPAR Technical Solutions V5R2 1345 Monroe NW Suite 259 iSeries Linux Technical Solutions V5R2 Grand Rapids, MI 49505 iSeries Windows Integration Technical Solutions V5R2 IBM eServer Certified Systems Specialist (616) 451-2500 iSeries System Administrator for OS/400 V5R2 (616) 451-2571 - Fax AS/400 RPG IV Developer (616) 260-4746 - Cell iSeries System Command Operations V5R2