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the difference between ALUA and symmetric active/active
HDS claims their AMS 2000 storage are symmetric active/active, EMC CX now support ALUA.
it seems they both can route I/O from the controller not own the lun to the owner controller.
so i'm really confused at what's the major difference between them?
bjpower
15 Posts
1
August 8th, 2010 00:00
From my understanding of the symms they don't have the same "ownership" set up as the clariions.
You provision/mask the luns to ports on the symm it does not matter what card they are on.
So you get the same effect as if you zone your hosts to multiple ports in a single SP on a clariion
ALUA on a clariion is different.
The host will only access the lun owning SP as any other failover setting.
If an issue occurs....
the IO request is sent to the non-owning SP this then gets routed through the CMI bus ( a connection between SPA and SPB using PCI or PCI express connection)
the owning SP processes the request and sends the response back through the CMI bus to the non-owning SP. the non owning SP then responds to the host.
dingding1
125 Posts
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August 8th, 2010 22:00
it seems the difference is, in symm mode, hosts can access lun via both SP. but in asymm mode, host can only access via the not owning SP only when the optimal path is failed.
jps00
392 Posts
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August 9th, 2010 06:00
bjpower's explanation is correct. ALUA is not a true active/active. Using ALUA, an I/O is serviced by the original SP which passes it to its peer for actual execution. This can occur for some time before the original SP's LUN is trespassed to the peer, because the ALUA path in 'not-optimal'. It uses more storage system resources and has a longer response time per I/O.
ALUA is described in the EMC CLARiiON Storage System Fundamentals for Performance and Availability whitepaper in the Availability section. This paper is available on Powerlink.
RRR
2 Intern
2 Intern
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5.7K Posts
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August 9th, 2010 07:00
So is the HDS AMS2k using ALUA or is it a true active/active system ?
jps00
392 Posts
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August 9th, 2010 08:00
The ams2xxx family is true active/active.
RRR, you keep on trying to get free consulting out of EMC on your HDS gear, and we're going to need a P.O.?
dingding1
125 Posts
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August 9th, 2010 17:00
but in AMS2k, there is also optimal path. LUN is also owned by CPU core, since CPU is owned by SP, it seems no difference compared to CLARiiON SP owned mode.
if lun is accessed via optimal path, HDS call it direct access, if not, HDS call it cross access.
after view the competition video "Trn_HDS_AMS2000-01_Symmetric_Active_Active-1209.mp4" in powerlink, i'm more confused at what's the real difference.
RRR
2 Intern
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5.7K Posts
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August 10th, 2010 02:00
Hahahaha, I am just curious ! I'm 100% for EMC, so if it was up to me, I'd replace the USP-V and the AMS1k and AMS2k3 for a CX4-960 !
Whenever HDS is here, I'm trying to figure out about their technology and compare it to EMC.
In fact I'm very curious about FASTv2 on Clariion, since we now could use that in this HDS empire ... HDS doesn't have a similar thing...
So Clariion is Asymetric A/A and AMS2k is Symmetric A/A ? Hmmmm... so the HDS guys were right then
dpm011
2 Posts
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August 10th, 2010 09:00
I heard Vmax isn't truly active-active but uses something similar to ALUA internally. Can anyone verify this?
It is reasonable to me since the previous Symms had a global cache, while the Vmax is distributed nodes like the CX. In a maximum configured Vmax, cache coherency would be very interesting if it truly maintains an active-active pathing method.
AranH1
2.2K Posts
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August 10th, 2010 09:00
That is completely wrong. The confusion lies in the fact that the CX4-960, VMAX, and VPLEX share a common base enclosure for the engines/storage processors. But the VMAX is truly Active/Active just like the DMX and previous Symms. Beyond the fact that the CX4 and VMAX arrays run entierely different Operating Code, the VMAX is implemented differently and has additional interconnets used for the cache coherency. The VMAX product guides are very clear on this and are easily downloaded from Powerlink.
AranH1
2.2K Posts
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August 10th, 2010 10:00
Yeah, I thought it was a VMAX when looking at the VPLEX during that demo.
... Hey it was good meeting you at the forums luncheon!
umichklewis_ac7b91
300 Posts
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August 10th, 2010 10:00
Thanks, much - same to you!
It was great to meet you and other users - I can't attend EMCWorld this year, but I'm hoping more forum users are able to attend. It's great to be able to put a name to a face!
Karl
dpm011
2 Posts
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August 10th, 2010 10:00
I glanced through the product guides but I didn't see it mentioned, do you have a link?
Thanks, D
umichklewis_ac7b91
300 Posts
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August 10th, 2010 10:00
Thanks for chiming in on this! I was utterly confused at EMC World about the similarities between VPLEX and CX4. It didn't help that I overheard a sales person say, "we'll basically they're the same, but very different, too"!
AranH1
2.2K Posts
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August 10th, 2010 11:00
If you are looking for good information on the VMAX arrays then these are two good documents to read:
Enginuity: The EMC Symmetrix Storage Operating Environment
Support > Technical Documentation and Advisories > Hardware/Platforms Documentation > Symmetrix VMAX Series > White Papers
EMC Symmetrix VMAX Series Product Guide
Support > Technical Documentation and Advisories > Hardware/Platforms Documentation > Symmetrix VMAX Series > General Reference
Are you looking for a statement from EMC stating that the VMAX is NOT an active/passive array? Why do you need this? Are you trying to build a case for or against a compteting product?