Updated 5/24/2010 – I’ve received some comments about expandability and I’ve received a correction about the speed of Dell’s memory, so I’ve updated this post.  You’ll find the corrections / additions below in GREEN.

Since I’ve received a lot of comments from my post on the Dell FlexMem Bridge technology, I thought I would  do an unbiased comparison between Dell’s FlexMem Bridge technology (via the PowerEdge 11G M910 blade server) vs IBM’s MAX5 + HX5 blade server offering.  In summary both offerings provide the Intel Xeon 7500 CPU plus the ability to add “extended memory“ offering value for virtualization, databases and any other workloads that benefit from large amounts of memory.

The Contenders

IBM
IBM’s extended memory solution is a two part solution consisting of the HX5 blade server PLUS the MAX5 memory blade.

• HX5 Blade Server
  I’ve spent considerable time on previous blogs detailing the IBM HX5, so please jump over to those links to dig into the specifics, but at a high level, the HX5 is IBM’s 2 CPU blade server that offers the Intel Xeon 7500 CPU.   The HX5 is a 30mm, ”single wide” blade server therefore you can fit up to 14 in an IBM BladeCenter H blade chassis. 
• MAX5
  The MAX 5 offering from IBM can be thought of as a “memory expansion blade.”  Offering an additional 24 memory DIMM slots, the MAX5 when coupled with the HX5 blade server, provides a total of 40 memory DIMMs.    The MAX5 is a standard “single wide”, 30mm form factor so when used with a single HX5 two IBM BladeCenter H server bays are required in the chassis.

DELL
Dell’s approach to extended memory is a bit different.  Instead of relying on a memory blade, Dell starts with the M910 blade server and allows users to use 2 CPUs plus their FlexMem Bridge to access the memory DIMMs of the 3rd and 4th CPU sockets.  For details on the FlexMem Bridge, check out my previous post.

• PowerEdge 11G M910 Blade Server
  The M910 is a 4 CPU capable blade server with 32 memory DIMMs.  This blade server is a full-height server therefore you can fit 8 servers inside the Dell M1000e blade chassis.

The Face-Off

ROUND 1 – Memory Capacity
When we compare the memory DIMMs available on each, we see that Dell’s offering comes up with 32 DIMMs vs IBM’s 40 DIMMs.  However, IBM’s solution of using the HX5 blade server + the MAX 5 memory expansion has a current maximum memory size is 8Gb whereas Dell offers a max memory size of 16Gb.  While this may change in the future, as of today, Dell has the edge so I have to claim: 

Round 1 Winner:  Dell

ROUND 2 – Memory Performance
As many comments came across on my posting of the Dell FlexMem Bridge technology the other day, several people pointed out that the memory performance is something that needs to be considered when comparing technologies.  Dell’s FlexMem Bridge offering reportedly runs at a maximum memory speed of 833Mhz,  runs at a max of 1066Ghz, but is dependent upon the speed of the processor.  A processor that has a 6.4GT QPI supports memory @ 1066Ghz ; a processor that supports 5.8GT/s QPI supports memory at 978Mhz, and a processor with a QPI speed of 4.8GT runs memory at 800Mhz.  This is a component of Intel’s Xeon 7500 architecture so it should be the same regardless of the server vendor.  Looking at IBM, we see the  HX5 blade server memory runs at a maximum of 978Mhz.    However, when you attach the MAX5 to the HX5 for the additional memory slots, however, the memory runs at speed of 1066Mhz, regardless of the speed of the CPU installed.  While this appears to be black magic, it’s really the results of IBM’s proprietary eXa scaling – something that I’ll cover in detail at a later date.   Although the HX5 blade server memory, when used by itself, does not have the ability to achieve 1066Ghz, this comparison is based on the Dell PowerEdge 11G M910 vs the IBM HX5+MAX5.  With that in mind, the ability to run the expanded memory at 1066Mhz gives IBM the edge in this round.

Round 2 Winner:  IBM

ROUND 3 – Server Density
This one is pretty straight forward.  IBM’s HX5 + MAX5 offering takes up 2 server bays, so in the IBM BladeCenter H, you can only fit 7 systems.  You can only fit 4 BladeCenter H chassis in a 42u rack, therefore you can fit a max of 28  IBM HX5 + MAX5 systems into a rack.

The Dell PowerEdge 11G M910 blade server is a full height server, so you can fit 8 servers into the Dell M1000e chassis.  4 Dell chassis will fit in a 42u rack, so you can get 32 Dell M910′s into a rack.

Round 3 Winner:  Dell

(NEW) ROUND 4 – Expandability
It was mentioned several times in the comments that expandability should have been reviewed as well.  When we look at Dell’s design, we see there two expansion options: run the Dell PowerEdge 11G M910 blade with 2 processors and the FlexMem Bridge, or run them with 4 processors and remove the FlexMem Bridge.

The modular design of the IBM eX5 architecture allows for a user to add memory (MAX5), add processors (2nd HX5) or both (2 x HX5 + 2 x MAX5).  This provide users with a lot of flexibility to choose a design that meets their workload.

Choosing a winner for this round is tough, as there a different ways to look at this:

Maximum CPUs in a server: TIE – both IBM and Dell can scale to 4 CPUs. 
Maximum CPU density in a 42u rack:  Dell wins with 32 x 4 CPU servers vs IBM’s 12.
Maximum Memory in a server: IBM with 640Gb using 2 x HX5 and 2 x MAX5
Max Memory density in a 42u Rack: Dell wins with 16Tb

Round 4 Winner:  TIE
Summary
While the fight was close, with a 2 to 1 win, it is clear the overall winner is Dell.  For this comparison, I tried to keep it focused on the memory aspect of the offerings. 

On a final note, at the time of this writing, the IBM MAX 5 memory expansion has not been released for general availability, while Dell is shipping their M910 blade server. 

There may be other advantages relative to processors that were not considered for this comparison, however I welcome any thoughts or comments you have. 

Okay, I can’t hold back any longer – I have more rumours. The next 45 days is going to be an EXTREMELY busy month with Intel announcing their Westmere EP processor, the predecessor to the Nehalem EP CPU and with the announcement of the Nehalem EX CPU, the predecessor to the Xeon 7400 CPU.  I’ll post more details on these processors in the future, as it becomes available, but for now, I want to talk on some additional rumours that I’m hearing from IBM.  As I’ve mentioned in my previous rumour post: this is purely speculation, I have no definitive information from IBM so this may be false info.  That being said, here we go:

Rumour #1:  As I previously posted, IBM has announced they will have a blade server based on their eX5 architecture  - the next generation of their eX4 architecture found in their IBM System x3850 M2 and x3950M2.  I’ve posted what I think this new blade server will look like (you can see it here) and  I had previously speculated that the server would be called  HS43 – however it appears that IBM may be changing their nomenclature for this class of blade to “HX5“.  I can see this happening – it’s a blend of “HS” and “eX5″.  It is a new class of blade server, so it makes sense.   I like the HX5 blade server name, although if you Google HX5 right now, you’ll get a lot of details about the Sony CyberShot DSC-HX5 digital camera.  (Maybe IBM should re-consider using HS43 instead of HX5 to avoid any lawsuits.)  It also makes it very clear that it is part of their eX5 architecture, so we’ll see if it gets announced that way.

Speaking of announcements…

Rumour #2:  While it is clear that Intel is waiting until March (31, I think) to announce the Nehalem EX and Westmere EP processors, I’m hearing rumours that IBM will be announcing their product offerings around the new Intel processors on March 2, 2010 in Toronto.  It will be interesting to see if this happens so soon (4 weeks away) but when it does, I’ll be sure to give you all the details!

That’s all I can talk about for now as “rumours”.  I have more information on another IBM announcement that I can not talk about, but come back to my site on Feb. 9 and you’ll find out what that new announcement is.