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тАО08-03-2004 04:27 AM
тАО08-03-2004 04:27 AM
Solved! Go to Solution.
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тАО08-03-2004 01:39 PM
тАО08-03-2004 01:39 PM
SolutionSo... how many FC ports to hosts does the array have? If four, you are limited to two different OSes, one per pair of ports. If 8, you can have up to four OSes, etc. 8 FC ports is normally the max for any "modular array" (everything except the big monolithic frames, EMC Symmetrix or HDS Lightning; both of these can do up to 32/64 FC ports, and are practically SANs in one box -- and they run their ports different than the modular arrays anyhow).
This limitation was well known and kind of stupid -- design limitations built into first or second generation boxes which were "good enough for starters", and indeed lots were sold (most to people with all SUN or all Windows or all HP-UX, so multi-OS wasn't a problem). But the current generation of modular arrays pretty much all have come up with ways around this, so that the FC port is now not given a special mode, but some virtual entity further into the array gets to do all the "special" stuff associated with a given OS.
HDS calls it "host storage domains", and it is assigned on a per LUN basis (you can do up to 128 different OSes in any Thunder 95xx array, with only two or four or eight FC ports).
HP EVA doesn't have this port-based limitation, although I believe that the older HP/CPQ arrays did. This is not a problem for modern STK arrays either. I'm not sure on the EMC Clariions, which used to have this as an issue, but surely must have found a way around it by now (one hopes).
One important consideration used to be licensing for different OSes cost money per OS. HP changed that, and now you can download a kit for any host OS they support, they are free. It doesn't appear to cost anything from HDS either, although you have to buy enough of their array SW to enable the "host storage domains" (once enabled, it works for any/all). STK gives you the first one for free, and then (last I heard) charges per OS after the first. So, on some arrays, lots of OSes can get expensive. But that's not a technical issue, just financial.
If the OS is assigned per LUN, the max LUN count could limit you. Again, in modern arrays, this is such a large number, it is immaterial to the question. Some older or low-end arrays can only do 16 or 32 LUNs, but I don't deal with them, or rarely.
That's all I can think of, hope it helps.
--bmr
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тАО08-03-2004 05:33 PM
тАО08-03-2004 05:33 PM
Re: What limits the number of OS's?
However there are limits on the number of hosts groups per CHIP port, number of total host groups per array, number of WWNs per host group.
sks
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тАО08-04-2004 06:18 AM
тАО08-04-2004 06:18 AM
Re: What limits the number of OS's?
And you're right, the big monolithic boxes are quite different in how their host ports function than the many modular arrays out there, including the HDS 95xx "Thunder" modular line.
In general, the Lightning arrays (like the big EMC Symmetrix units) can present all LUNs out of any and all ports simultaneously, with no ports limited to any given OS. Modular arrays, on the other hand, can only present LUNs out of the ports on one controller at a time, with the other controller as a hot standby in case of failure.
This concept of "LUN ownership" by one or the other controller is one of the major differences between modular storage and the big monolithic arrays. As I said before, however, it is rare these days to find that this also limits how many OSes can be serviced by one array or FC port, modular or monolithic.
Regards, --bmr
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тАО08-04-2004 09:33 AM
тАО08-04-2004 09:33 AM
Re: What limits the number of OS's?
I wanted to thank everyone for their input, all information that everybody has provided has really helped me in getting a better grasp on this.
Thanks again,
Scott