HP XP1024 vs EMC DMX

[Miguel Angel Aliaga_1]

Hi all,
we are evaluating to change our HP XP256`s this year. Our options are HP XP1024 and the new EMC DMX1000.

Any bad/good experience on XP1024 ????

Any comment about the new EMC DMX ?????

Regards.

P.S. This thread has been moved from Disk to Storage Area Networks (SAN) (Enterprise). -HP Forum Moderator

[Vincent Fleming]

There isn't much out on the DMX since it was just announced. We'll have to wait and see for real-world experiences.

Meanwhile, IMHO, the DMX is a nice upgrade to the Symm design; but they didn't fix any of the real problems that the Symm architecture has always had; for example:

They *still* don't mirror cache - cache boards are a single point of failure. Ask around about this - I have several customers that have experienced such failures and have lost data.

They *still* haven't implemented RAID 5 in the Symm (the Clariion has it). Their RAID-S (now called "Parity RAID") is a poor performer in comparison to the XP's RAID 5, or even EMC's own RAID-1. EMC rated RAID-S at 15% of the performance of RAID-1.

They still don't implement RAID 0/1 (or RAID 10, RAID 0+1, or whatever you want to call it - striping mirror pairs) for Open Systems - only Mainframe volumes can use it.

They still battery-backup the entire array; sold as a "feature" for greater data protection, they keep the disks spinning so they can destage cache to the disk media on power failure. Nice idea, in theory. The problem is that the batteries take 12 HOURS to recharge! What happens if you have multiple, consecutive power failures (very common around here) within a 12-hour period? Data loss, that's what.

In comparison, the XP mirrors cache as well as ECC protection on ALL copies of your data.

The XP implements RAID-5 with performance equal to about 85% of the performance of RAID-1.

The XP has RAID 0/1 for Open Systems as well as Mainframes, in two flavors - 4-drive and 8-drive.

And, the XP battery-backs the cache only, so you can sustain multiple, consecutive power failures without data loss.

As for the difference in bandwidth between DMX and XP, well, I haven't seen an XP1024's busses get saturated yet. It has plenty of bandwidth. I don't see how more than that helps.

Well, that's my opinion. I'm sure there are lots of people out there that think differently, but you asked for opinions/comments.

Good luck, and thanks for considering HP in your purchases!

Vince

[Miguel Angel Aliaga_1]

Thanks, Vince.

I agree with U in everything. Probably, the cost will be an important factor on this decision.

Six moths ago, EMC engineers tell me that their systems didn`t need a better performance cause applications don`t demand it.
Now, their systems are the best.Oops!!

I think that EMC systems are very goods ( on the paper ), but I think that XP1024 are too.
EMC has a good new product but, I think too, that they must mirror their cache. This is a critical point of failure.

Thanks again Vince.

[Brian M Rawlings]

Hi. I believe there is a misconception about Symm cache -- if any single memory board in a Symm fails, the frame keeps on running, memory is 'raid' protected by ECC across multiple boards. If two memory boards fail, it is not correctable in Symm or in Hitachi/XP (unless the exact right two cards fail so that their mirrored partner is left intact on the XP. What are the odds?).

This is actually analagous to raid-5-protected disks. Is a disk a single point of failure? Well, yes, because it could fail, but, no, because its failure causes no issue with array operation or access to your data. Same with Symm memory.

If two drives fail, you are not designing against that, and odds are you will lose data. If you mirror only, your odds of surviving a two-component failure go up, but not a whole lot.

It also turns out that mirroring the cache results in a bandwidth reduction through cache, which every read or write uses. Every transaction takes a performance hit.

As to RAID-5 support, EMC claims their "parity RAID" in DMX to be the highest performing in the industry, apples to apples. Nothing like RAID-S. It would be interesting to benchmark them.

DMX uses their new "direct matrix" internal I/O structure, claiming it to provide the best throughput in the industry. Again, interesting new stuff, appears to be very fast, eliminating the "blocking" issues that a crossbar switch inherently has to deal with. It would be fun to benchmark them side by side, size for size, host for host.

As far as customers losing data due to Symm or Hitachi failure of some kind, I've heard of both, and both are quite rare. The two things I've heard that differentiate them is, 1> the level of support overall, which seems to side with EMC, and; 2> the reality and maturity of the various Software offerings from each vendor definatly weigh toward EMC.

DMX looks very interesting, and, depending on where pricing comes in (reputed to be very competitive, but we'll see), it could be tough to beat.

--bmr

[Bill McNAMARA_1]

go directly to hitachi too, that'll help you bargain the hp price down.

Price will be less of an issue then.

Of course, you're not going to get a non-biased opinion here - in either case, you're going to end up with a good product.

Later,
Bill

[Bill McNAMARA_1]

see http://www.hds.com/

[Miguel Angel Aliaga_1]

Thanks Bill, but the support of Hitachi in Spain, specially in my town is very poor. Otherwise, HP give us a hardware engineer in our site.

[Bill McNAMARA_1]

Thats not my point, you can get a quote from hds and then bargain hp/emc when you see the price difference.

[Vasudevan Ramaswami]

I am in the same situation as Miguel Angel Aliagaam the only difference is looking for a replacement for Symm5 - We have spend enormous time on studying the replacement between "DMX/ XX1024 / SUN-HDS V9980" - While I would agree with Vincent Fleming on most of things, most bothering issues to me about the DMX are the limitations on this box specially to me the protection on the BCV is a big deal as I am looking at 4 BCVs for the production to run my testing / integration and burn database copies of my SAP database of 2 TB, While XP allows me to select the RAID1 for the production and RAID5 for the BCVs - DMX my only choice for the production is RAID1 no matter what my production???s RAID is - what it means to me is that I need to buy more raw disk for the DMX than XP to get the same usable disk, on the long run the my running cost would be high. Other limitation is the SRDF - timestamp security issue, EMC still don???t have this while XP it is secure.

Good luck - this is my 2 cents.

[Dave Wherry]

Both products are good. I've had good and bad experiences with both concerning support. The DMX does not make any significant leap ahead of the XP in performance or features. Some will and have argued that it is still behind the XP.
Did your current XP do the job for you? To me you already have a knowledge investment in the software. If you go DMX you have a new learning curve in front of you. Change for the sake of change never made sense to me.
Of course EMC can get very aggressive in price when they are trying to displace a competitor.