HP UNIX 11.00: Max Number Of Disks/LUNS - EMC Symmetrix

[LG Porter]

I have several HP N4000 class servers configured in a MCSG 11.12 three node configuration attached to a EMC 8730 Symmetrix array. Is there a maximum number of physical disks and LUNS that a HPUX 11.0 can address? Is there any white papers, or configuration guides available outlining the limits associated with this type of configuration?

[monasingh_1 · Accepted solution]

HPUX can handle lot more LUNs than EMC can support. It uses virtual bus funda after it reaches target/lun as ff , one the same physical channel it creates a vertual bus 1,2 ,3 and so on and starts again from 00 to ff for each virtual bus. So HPUX 11 is not any issue without any patch even. EMC I rhink has a limit of 256 or 255 per fiber channel..

[monasingh_1]

sorry about that ff, It is f7 (target/lun)..

[James R. Ferguson]

Hi:

Have a look at this:

http://docs.hp.com/hpux/onlinedocs/netcom/maxlun-whitepaper-v1.0.pdf

Regards!

...JRF...

[Chris Vail]

We have 157TB of EMC disks here, and haven't (yet) run out of numbers to use. Of course, when I call HP and tell them I'm having trouble with c136t3d0, they usually freak out. AFAIK, you can have 1024 devices on the channel. This is because HP-UX virtualizes the addresses.

And if you do run out of disk addresses, make sure the EMC salesrep gives you a really nice T-Shirt. He'll have sold you A LOT of disks.........


Chris

[Steven E. Protter]

I think you are okay with EMC

Some other non-HP disk arrays have an 8 LUN per fiber card limit. This is a problem with the driver for card and how it relates to the SAN.

There has been an enhancement request for well over a year to deal with this issue from HP.

Still waiting.

SEP

[Ross Zubritski]

EMC will only support 256 luns per channel.

Regards,

RZ

[Vincent Fleming]

In a practical sense, HP-UX does not have a limit to the number of LUNs that you can see overall; there is a limit to the number that can be seen *through a specific card*, but you can have more than one card.

I have heard, however, that if HP-UX has *a lot* of LUNs, it can degrade performance somewhat because the kernel gets bloated with all those devices. What's *a lot*? I don't remember, but it was high - over 768, as I remember.

Perhaps someone here remembers.

How much storage are you planning to put on that N4000?

Vince

[John Thykattil]

But what is the max target and LUN numbers for a single HBA?

That is,

cXtYdZ

- max Y?
- max Z?

Thanks.

[Vincent Fleming]

Your max Z (virtual LUN #) is 7... this is how they get numebered:

c1t0d0 - lun 0
c1t0d1 - lun 1
c1t0d2 - lun 2
c1t0d3 - lun 3
c1t0d4 - lun 4
c1t0d5 - lun 5
c1t0d6 - lun 6
c1t0d7 - lun 7
c1t1d0 - lun 8
c1t1d1 - lun 9
etc, etc.

I think the max Y (virtual target#) would be 64 for any given target or HBA, giving you 512 devices. (I've never seen anyone put that many devices on a single HBA, so I'm guessing a little on the target#).

Vince

[LG Porter]

Hi Vincent: Would that same LUN assignment apply to fiber channel attached as you outlined for HBA attached? Now scsi ID assignments follow the 0 - 8 and 9 -16 being the highest is the order of priority..... right? So if I understand it, there is a possiblity of having 256 physical disks configured to a single LUN?