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XP12K vs XP24K

Honored Contributor

XP12K vs XP24K


Did a quick search but could not locate the information I am looking for.

Would anyone have good documentation on the differences between XP12K and XP24K ?

Also, I would appreciate any links for key differences between EMC DMX vs XP (Hitachi) 12K/24K or even 48K.

I know of few major differences between EMC and XP including Direct Matrix vs XP's Cross-bar switch, but looking for something more comprehensive.

Any help will be appreciated !!

Learn What to do ,How to do and more importantly When to do ?
Honored Contributor

Re: XP12K vs XP24K

Hi, one of the main differences between the XP12k and XP24k firmware is the XP24k new feature - Thin Provisioning (ThP)
, which is intended to give us more flexibility in the Storage allocation. It is something like the EVA virtualization and automatic load redistribution. Currently it supports the BC and we are waiting for the CA support. An independent XP24000 IOPs test is available on the http://www.storageperformance.org/results/a00056_HP_XP24000_executive-summary.pdf and the full disclosure report is here:
there is a standard information at:
There is a brief comparison of the DMX and XP12 here Q4/A4 here:

The XP disk arrays (including the XP12000) are not "monolithic" or "mainframe". The XP is more modular and flexible than EMC's "monolithic" DMX. For instance with the XP you can add disks, processors, cache, disk racks, and host interfaces as you like while it is running with no application downtime - that's pretty powerful for today's mission-critical, 24x7 applications. Compare that to EMC's DMX, to scale from their lowest to their highest configuration requires swapping through several different models. Each EMC DMX only covers half the solution space the XP12000 covers with just one model. To differentiate the XP disk arrays from monolithic, 'fork-lift' upgrade solutions like EMC's DMX, we describe the XP disk arrays as "frame-based". The XP12000 is NOT a monolithic array.
XP 12k best practices for performance guidelines is here:

the pain is one part of the reality
Vincent Fleming
Honored Contributor

Re: XP12K vs XP24K

Most of the differences between the XP12k and the XP24k are evolutionary in nature, and most are hardware items:

1. faster microprocessors - they went from 400Mhz to 800Mhz processors throughout
2. 4Gb backend FC loops
3. 1/2 height cards throughout - all the CHIP and ACP pairs, cache cards, sm cards, etc are all 1/2 the size they used to be - so there are twice as many of them now.
4. upgraded SVP hardware
5. power changes - they went from all-48vdc in the XP12k to having multiple voltages of DC. This includes changes in Batteries required in different configurations.
6. lots of enhanced software features
7. load sharing MPs - the microprocessors on the frontend share the load amongst themselves as well as passing some workload to the backend now. This translates into significantly better throughput, regardless of workload.

Highlights on why XPs are better than DMX's:

Replication - XP replication spanks DMX. Hard. XP asynchronous replication has been out in the field for more than 7 years. DMX? about 1.5 years. XP asynch has a significantly lower RPO (Recovery point objective) - nearly zero data loss. EMC can only guarantee about 1 minute of data loss at best. (a LOT can happen in a minute) XP also has Journaling CA, which EMC's SRDF hack just can't compare.

Zero-downtime Microcode upgrades - XP does not need to shut down even a single FC port to upgrade the firmware. Even single-attached hosts are completely unaware that a firmware update has occured. EMC can't do this at all - it MUST stop doing I/O on a port to upgrade the FW.

Thin Provisioning - EMC is dreaming of doing this someday. ;^)

FC ports - XP has 2x the FC ports of the DMX on the frontend. (128 vs 64 for DMX)

External Storage - another feature that EMC dreams of - hang cheaper storage off your XP to use for Business Copies or other Tier-2 and Tier-3 uses. Use it for Virtualization!!! Data Migration, too!

Mirrored Cache - XP mirrors ONLY write data in the cache - read data is not mirrored. DMX mirrors EVERY BYTE of cache. A DMX needs nearly 2x the cache of an XP to cache the same amount of data - and cache is EXPENSIVE! Especially when you're looking at 128GB - you would need 256GB from EMC to hold 128GB of data - with XP you need only 128GB.

Well, that ought to get you started. ;^)


No matter where you go, there you are.
Gar Dinneen
Occasional Visitor

Re: XP12K vs XP24K

Hi Sundar,
Which of EMC's DMX range of arrays did you want to compare with XP. What are you trying to compare? H/W design, S/W functionality? Can you be more specific? What do you know already, so that we can build on this?
Nigel Poulton
Respected Contributor

Re: XP12K vs XP24K


XP12K versus XP24K on this forum â fair enough

XP versus DMX on this forum.... what kind of answer do you expect? Its like going to your local karate dojo and asking if karate is better than ju-jistu. Youâ re going to get biased responses.

Let me just clarify a couple of things that I think are a bit misleading â

1. The DMX ships thin provisioning, they call it Virtual Provisioning. And if you know anything about thin/dynamic provisioning you will know that the devil is in the detail. I see no mention here about the XP24Kâ s very large 42MB extent size (they call it "page" size but may be â bookâ is more appropriate than â pageâ ) compared to everybody else, including EMC having a â pageâ size below 1MB. You might wonder how optimal the XPâ s 42MB page size is!!?? So far as zero page reclaim and wide striping goes, 42MB seems very chubby and not optimal. 42MB is mathematically convenient for the XP but â convenientâ and â optimalâ are not always the same. My blog talks about the 42MB page size if you dont already know why it is 42MB.

2. Software for the EMC is far better than for the Hitachi kit. No doubt about that. CommandView and CV Advanced as well as TuningManager (cant remember the HP name) etc suck.

3. Can IBaltay please explain how â each DMX only covers half the solutions space the XP12000 covers....â . This is an interesting statement that needs qualification. Im genuinely interested in hwo this is true???

4. As for the XP having twice the amount of FC ports of a DMX....... there is no mention of the superior processors behind the front end ports on the DMX (DMX=1.3Ghz PPC whereas the XP has 800Mhz MIPs â men against boys?). Granted that the XP offloads BC operations and RAID calculations etc to back end processors. But simply saying the XP wipes the flaw with the DMX on the front end is not a fair assessment. Its akin to saying the DMX beats up on the XP at the back end because it supports more disks. Very misleading.....

5. I do not believe that EMC dreams of doing external storage. While external storage is a very innovative offering from Hitachi, it requires very little in R&D. The following is an oversimplification, but Its probably not that different to qualifying an new HBA for working with your system. The XP just acts like a Windows 2000 host to the external array. If EMC really dreamed of doing this, they would have done it by now as its technically not that hard to do.

6. The DMX has supported and shipped SSD for over a year now. I see zero XPs out there with SSD. In fact HDS only annouced suuport for SSD nearly year after EMC shipped. This is a big differentiator in my opinion in the favour of EMC. SSD wipes the floor with rotating magnetic media when it comes to seek times (non-existent for SSD) and read miss conditions in cache.

At the end of the day, the XP and DMX are both great storage arrays. They are in a class of their own. But they go head to head every day and some times the DMX wins and sometimes the XP wins. Now if you were comparing the XP to the IBM high end DS8x00 range that is a different matter. The XP wins hands down nearly every time. But in conclusion, the XP and the DMX are both great and have their own strengths.

This is may be not the best forum to ask for balanced opinions.

Now Im not an EMC, HP or even HDS employee. Im not trying to knock the XP, in fact I blog about the XP (HDS USP-V) and think its good storage. You will find what I believe is the best information on the XP available on the internet on my blog site. You want to know how the XP works under the hood check out my blog (ThP, RAID, caching etc.....). Check it out â


Im just trying to balance this biased conversation.

Talk about the XP and EVA @ http://blog.nigelpoulton.com