Re: IBM FastT vs. EMC Clarion
From: Vincent D'Antonio (dantoniov_at_gmail.com)
Date: 03/28/05
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Date: Mon, 28 Mar 2005 10:15:58 -0500 To: aix-l@Princeton.EDU
I received this from EMC on 3/15/05, I do not know about the CX700 as
I have only the CX300 and CX500.
Thanks
Vince
On Mon, 28 Mar 2005 10:09:02 -0500, Clifton, Pablo
<Pablo.Clifton@bcbsfl.com> wrote:
> Vincent-
> Does the EMC announcement pertain to the CX-700 Clariion also? And how
> long ago did you receive that info from EMC?
>
> thanks,
> pablo
> ---
> Pablo Clifton
> Storage Administrator
>
> -----Original Message-----
> From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
> Andrew Townsend
> Sent: Friday, March 25, 2005 8:43 AM
> To: aix-l@Princeton.EDU
> Subject: Re: IBM FastT vs. EMC Clarion
>
> This is true. AIX hosts have to be shutdown when doing the firmware
> upgrade on the Clariion.
>
> "Vincent
> D'Antonio" To:
> aix-l@Princeton.EDU
> <dantoniov@gmail. cc:
> com> Subject: Re: IBM FastT
> vs. EMC Clarion
> Sent by: IBM AIX
> Discussion List
> <aix-l@Princeton.
> EDU>
>
> 03/25/2005 07:55
> AM
> Please respond to
> "Vincent
> D'Antonio"
>
> I have two CX500's and 5 CX300, not by my choice, I go with IBM. THe
> big thing I found is that if you need to do a flare upgade (firmware)
> any AIX servers attached to that unit will have to be shutdown. That is
> as of today. I do know EMC has made some improvment to powerpath to
> help but still not there yet. The trouble is something with the OS and
> the disk, when they do a flare upgrade on the A side sometimes and not
> all, the disk are gone from the OS and you have to reboot to get them
> back. Again managment are the ones that whated EMC here and it is a
> show stopper in rolling out a new product till it is fixed.
>
> Here is a copy from EMC on this issue:
>
> EMC Corporate Statement
>
> The EMC CLARiiON CX family of arrays supports a Non-Disruptive Upgrade
> process (NDU) for upgrading the software on the array without
> interrupting host I/O access to the array. This process involves
> upgrading the software on the array storage processors one at a time,
> while allowing the other array storage processor to continue to service
> I/O requests. EMC has successfully tested this process without
> interrupting host I/O access to the array thousands of times with many
> different types of hosts attached to the array. Unfortunately, we have
> found that in a small percentage of cases upgrading the array software
> will cause interruption in host I/O from AIX attached hosts.
>
> Because even a small percentage of failures is unacceptable to customers
> who depend on the non-disruptive nature of our array software upgrades,
> EMC's current recommendation is to schedule software upgrade for arrays
> with AIX attached hosts at a time when AIX host I/O interruptions can be
> tolerated. EMC has a cross-functional team including members from
> several EMC Engineering organizations and EMC Customer Service, along
> with assistance from IBM to address the failures. The problem is related
> to complex interactions between AIX driver behavior, PowerPath behavior,
> and CX array behavior that have been difficult to reproduce for root
> cause. Due to this complexity, progress thus far has been slow. However,
> EMC is committed to the same NDU feature for AIX attached hosts that is
> currently available for other attached host environments.
>
> EMC has equipment and staff dedicated full time to these efforts and is
> committed to delivering reliable NDU for AIX as soon as possible.
> Current Status
>
> EMC has made tremendous progress in addressing the ability to
> successfully and safely perform online NDUs in an AIX attached
> environment through changes in PowerPath. We are constantly running NDUs
> in our lab and we now have runs of as many as a 100 consecutive
> successful NDUs under heavy host I/O load with hundreds of paths to the
> array. However, we still have occasional failures.
>
> We have reached agreement with IBM engineering on an approach to
> addressing the problem that involves changes in array behavior combined
> with changes in PowerPath behavior. We are in the process of
> implementing and then testing the changes. We are optimistic that these
> changes will enable reliable NDU for AIX. However, to assure the changes
> enable successful NDU and do not introduce new problems, extensive
> testing will be required. As we complete our implementation and get some
> testing completed, we will have a better feel for the success of this
> approach and will start to plan how to deliver the updates to the field.
>
> Additional information should be available in the next 30 days. We
> remain committed to reliable NDU for AIX ASAP.
>
> HTH
> Vince
>
> On Thu, 24 Mar 2005 23:25:50 -0500, Jim Richard <JRichard@sciquest.com>
> wrote:
> > I have a fastt600 running for a year now flawlessly... My only gripe
> > is
> that
> > it was advertised as being raid 10 aka (1+0) capable... And
> > technically
> it's
> > not. To my mind raid 10 is Mirror the disks across pairs then stripe
> > the data across the mirrors. IBM builds the stripe on half the disks
> > then mirrors the entire stripe onto the other half of the physical
> disks.
> >
> > This has a number of negative reliability, and recovery ramifications
> :
> >
> > Reliability:
> >
> > In my idea of a raid 10 ( and most other vendors' that I've
> dealt
> > with ) you would have to loose 2 individual disks that are
> directly
> > paired together to loose the array.
> > So say you have a disk array with 10 drives, this would be
> comprised
> > of
> > 5 pairs.
> > You would have to loose both disks of any single pair for the
> array
> > to fail. So I can actually have up to 5
> > disks of the 10 units fail before the array fails (very best
> case),
> > so long as no two failed disks were paired together.
> >
> > In IBM's idea of a raid 10 you have an array comprised of 5
> > drives striped ( raid 0) then the raid 0 is mirrored
> > to another 5 drives (raid 0+1).
> > In this case if you loose 1 drive on one stripe then any other
> drive
> > on the other stripe the
> > array is toast. The only way to lose 5 disks and have the array
>
> > survive is if all 5 failed disks are in the
> > same stripe. Of course the only likely scenario for this is if
> your
> > stripes are in two separate disk enclosures, and
> > you lose an enclosure. Which is a good idea in either case, in
> > my idea of a raid 10 no paired disks would reside in
> > the same enclosure.
> >
> > Recovery:
> >
> > In my idea of a raid 10 described above, if you loose a drive,
> when
> > you replace it only the one drive has
> > to be re-mirrored.
> >
> > In IBM's idea of a raid 10, the entire 5 drive stripe has to be
>
> > re-mirrored...5x I/O, CPU, contention on the
> > switch .... Etc.
> >
> > To be fair you can mitigate most of the reliability risk with proper
> > use
> of
> > hot spares and diligent monitoring, which should be the norm in any
> > large disk deployment SAN, SCSI, or anything else. Unfortunately the
> > recovery issue is still a problem for large arrays.
> >
> > Unfortunately for me the decision to purchase these units) was based
> > on
> high
> > level marketing material and discounts... I only found all this out
> > after slogging through the technical docs ( and this little detail is
> > buried
> way
> > down in them) after the equipment was already on order. A typical
> > case
> of
> > buyer beware.
> >
> > Other then that the stuff is pretty nice. If you're not planning on
> running
> > raid 10 (1+0) you should be fine. If you are going to run mirrored
> > you'll
> be
> > fine as long as you follow best practices and understand the issues.
> >
> > Jim
> >
> > -----Original Message-----
> > From: glh@DAIRYNET.COM [mailto:glh@DAIRYNET.COM]
> > Sent: Thursday, March 24, 2005 12:31 PM
> > To: aix-l@Princeton.EDU
> > Subject: IBM FastT vs. EMC Clarion
> >
> > We are in the process of selecting our first SAN for our environment -
>
> > approximately 10 AIX servers and 3 Windows servers. We've narrowed
> > our choices down to either an IBM DS4300 Turbo (old FastT) or the EMC
> CLARiion
> > CX500. For those of you who may have worked with either (or both) of
> these
> > products, what is your overall opinion of the product? Would you buy
> that
> > product again? Any positive or negative comments would be greatly
> > appreciated. Thanks.
> >
>
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- Previous message: Clifton, Pablo: "Re: IBM FastT vs. EMC Clarion"
- In reply to: Clifton, Pablo: "Re: IBM FastT vs. EMC Clarion"
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