amount of disk devices

[Bill Hall]

Anthony,

The 256 LUN per HBA is a documented limitation on the EVA series of arrays. The EVA arrays can present a maximum of 256 LUNs to a single HBA, IIRC the HSG80 based arrays were limited to only 128. Consider also that the EVA can present a relatively low total number of LUNS (1024???), but I consider it much more flexible and easier to manage than the XP arrays.

I have never seen a similar limitation published for the XP series of arrays.

Rob has verified that VMS does not impose a 256 device per HBA limit. Hoff has supplied the current unit number limits both MSCP served devices and non-MSCP served devices. Hoff also brings up a valid point about the manageability of a large number of small devices vs. a smaller number of large devices.

Bill

[Jan van den Ende]

Anthony,

another point of consideration.

This looks like big fiture planning.

Do _NOT_ assume that current limits are fixed!

Of course, on current hardware stay within the current limitations, but as Bill already remarked, those are different for EVA and XP.

So, _NOW_ design for future growth!

How to do that, requires MUCH more info, which you should have (to be able to DO the job.

Just ALWAYS keep in mind to NOT lock yourself out of future developments.

(when we set up our current cluster, nobody had heard of SANs, but we migrated towards using it without a single second of downtime).

Wishing you success, and much wisdom.

Proost.

Have one on me.

jpe

[Anthony Pratico]

Thanks Guys for you input, you are correct this for for now and future planning and growth, and of course I do not want to lock out of any future changes.

By doing what we and HP are planning, we are trying to minimize or eliminate the perceived downtime updating our DRC and to actually have as close to a HOT site as possible.

Thanks All!

[Doug Phillips]

Anthony,

My point was pretty obscure, I guess: You need to be looking at real numbers. Like actual storage volume rather than than just number of disks. Do you really expect to have more volume than can be stored on 32K disks? What size are your disks and partitions? Should you maybe be looking at larger disks?

Use a realistic allocation of the DG assignments. You want to group them by production and DRC allowing for 30K each? Is that realistic? Would 10K or 15K per-group be enough? If not, then, you need to go another direction (as mentioned by others.) If you're really talking about that size need, then you must have a *very large* budget.

How much growth do you *really* expect to have in the future; say 3 to 5 years? Double that number if you want to. Then, decide if you need to take another approach. Also consider the advancements in storage technology that we might see in the future. Chart the curve back 5 years and project it forward to get the idea.

The fact that the XP12000 *can* create 500,000 drives is irrelevant if you are never going come close to using that many. If you do expect growth that will exceed 32K per DGA and 256 disks per HBA, (I'd love to see that installation when you get it up and running!) then look at other options.

[Guenther Froehlin]

We aer not talking about max disk unit numbers, aren't we? Like a scheme to number shadow set members nicely by using high digit numbers to identify them as being shadow set members of the same shadow set?

/Guenther