Backend and Hyper question for VMAX

Question

We are in the process of purchasing a new VMAX array for which we have to do some POC, hence I was doing some research and had the following questions Backend connectivity from DAs to DAEs Is there any kind of information in powerlink showing how the cabling is done on the backend? Split/Hyper size consideration I found a couple of threads which talk about dividing a disk into 255 splits (some say planning for this 255 number is not good and 128 is a better number)but what I would like to know is that if there is anything wrong in configuring only let’s say 10 or 20 or 30 splits per disk and still utilize the total space of the disk. What are the criteria based on which hyper size is decided. Any kind of input is much appreciated.

Quincy561 · Accepted Answer

If you create a single RAID1 volume, there will be two hypers created on two disks. The size of the hypers will be the size of the volume asked for.

If you create an 9GB volume with RAID5 3+1, you will create 4 hypers on 4 disks each with 3GB.

So you need to figure out how many volumes to create so all 30 disks have the same number of volumes on them.

Somewhere around 8 hypers will be optimal for performance. Even numbers are good for the RAID1 volumes.

Each DA has two ports. Each DA has a partner that is used for failover. Both are active with every other disk being assigned to a specific DA by default. A given DAE is cabled to a specific DA CPU. You can get the DA assignments by doing a symdisk list command. It shows the Director, CPU letter, and interface (port) the disks are connected to.

Quincy561 · Answer

Please let me know where you saw that 255 or 128 hypers is a good idea, because I'd like to squash that. That many hypers may be supported, but are not optimal for performance.

Are you using VP or traditional thick volumes? What size drives? What protection?

If you send me a PM with the Symm serial # I could send you back a picture of the backend layout of disks.

Sridhar246 · Answer

I should have put it in better words, they were just doing the calculation based on 255 splits/disk which I confused with actual design numbers....my bad

We don't have the array with us right now I was just curious as to how things work.

For this discussion, lets say I want to create two disk groups each with 30 disks (450 GB 15k RPM) Thick provisioned one disk group will be R1/0 and other R5 (3+1). How will the hyper size be decided?

Also, I am intrested in the actual backend cabling from DAs to DAEs.

vforde · Answer

Hi Quincy,

So am I right in saying so for a disk group with 450GB drive destined for Raid-5 (3+1) if the disk group is destined for thick volumes is a Thick volume size of 168.75 (break down below) correct?

168.75 = 56.25 (450G drive /8) x 3 (the data stripe number)

and if the disk group is destined for Virtual/Thin provisioning the TDAT size for the Raid5 (3+1) pool should also be 168.75?

Thanks,

Victor

Quincy561 · Answer

Yes, eight 167.75 GB volumes 3+1 RAID5 would fill the disks and give you eight splits per drive.  This would work well in a VP environment, or also in a thick environment.  Sometimes a thick environment will have specific volume sizes the host needs, so this might need to be changed to match what the hosts require.  For VP, the TDEV size is not tied to the backend TDAT size.

vforde · Answer

Thanks for the confirmation Quincy. Helpful as always.

VMAX

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