Re: Disk requirement (performance-wise) on a Power 7 replacing a System i 520

Larry,

What are your thoughts on using RAID-6 instead of RAID-5 with Hot Spare ?
(Assuming disk busy % isn't that high).
I just don't like the idea of a disk sitting there doing basically nothing when it could be providing additional protection and another arm to spread data over.

Haven't done that with "spinny" disks, but did a new box recently with 256GB memory and 18x387GB SSD's (all in an EDR1 Ultra-SSD Drawer drawer and protected with RAID-6). What a screamer !!

Anyway, for Jeff's smaller system situation, at only US$498 each you may as well fill out the CEC with 8 x 139.5GB 15k RPM disks.
Whether one is a Hot Spare and there are 7 active in the RAID-6 set, or you have RAID-6 with all pulling their share.

I also like the suggestion, if disk % busy isn't too high and 558GB of usable disk is enough, of getting better protection by going to 8 x 139.5GB disks in a Mirrored instead of RAID configuration.


Neil Palmer, Waterloo, Ontario, Canada

(This account not monitored for personal mail,
remove the last two letters before @ for that)

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On Tue, 10/22/13, DrFranken <midrange@xxxxxxxxxxxx> wrote:

Subject: Re: Disk requirement (performance-wise) on a Power 7 replacing a System i 520
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Received: Tuesday, October 22, 2013, 1:17 PM

Add to Roberto's comments that the
36G drives came in 10K RPM and 15K
RPM flavors. You probably have 15K Units (FC #4326) but not
for sure.

Remember that too few drives can really cripple your
performance,
despite vastly more CPW if you can't get to the data you're
hosed!

Also remember the price of drives now is fabulously lower
than those
older drives when they were new! So I always recommend that
you start
with 8 drives in a RAID 5 with hot spare configuration.

One 'simple' thing to do is on your system do WRKDSKSTS.
Wait 5 minutes
and do F5. Then look at the % Busy column (far right.) Tell
us what
those numbers are. DO do this when the system is at it's
busiest time so
you get numbers that are reasonable.

If what you see is 40 and 50% or higher (not likely) then 8
arms will
never be enough. If you're seeing 1s and 2s though then 8
will be fine.

One more thing. MEMORY. It's cheaper than ever, get a lot.
It helps disk
business a lot!

         - Larry "DrFranken"
Bolhuis

www.frankeni.com
www.iDevCloud.com
www.iInTheCloud.com

On 10/22/2013 1:08 PM, Roberto José Etcheverry Romero
wrote:

16drives on a 520 means you have at least one 0595 and

drives on both

the CEC (with it's sucky 40mb controller) and the 0595

(with a wide

range of controllers).
I would think that any controller at the p7 level would

stomp the

ground with those. I'm not so sure on the disk arm

side, i keep

reading that a bare min would be 6 arms...
To be able to compare properly you would need to get a

rack config, or

at least list the disk controllers and which drives are

hooked up to

which controller.
And check which controller would be on the power7

machine...

Best Regards,


On Tue, Oct 22, 2013 at 2:00 PM, Jeff Crosby <jlcrosby@xxxxxxxxxxxxxxxx>

wrote:

All,

I've asked a BP for a quote on a Power 7 to replace

our System i 520,

thinking that maybe the 3 year cost wouldn't be

much more than the

maintenance alone on the System i.  Haven't

received the quote yet, so I

don't know if I'm delusional or not.

Anyway, the System i has 16 ~36gb drives at only

20% capacity.  IOW we only

have 98gb data on the System i.  Isn't the

smallest drive available on the

Power 7 larger than that?  At a minimum I

would want 4 drives, raided, with

a 5th as a hot spare.  Any way to tell the

performance, disk-wise, of that

system as compared to our current system?

Thanks.

--
Jeff Crosby
VP Information Systems
UniPro FoodService/Dilgard
P.O. Box 13369
Ft. Wayne, IN 46868-3369
260-422-7531
www.dilgardfoods.com