How many Hypers in a Meta Device

Question

What is EMC's Recommended practise for the Number of Hypers in a Meta Device. Does it matter on the number of hypers as long as care is taken that no 2 hypers overlap over the same physical disk ?

RRR · Accepted Answer

I think you meant to ask about the number of symdevs in a meta. In a single symdev there are a number of hypers / slices. Each meta consists of a number of symdevs.
I've had discussions with a Symm performance guru about this and what we came up with is that the number isn't that important as long as you don't have an overlap on the same physical disk. With "symdev show " you can check out the physical disks involved with each hyper or slice withing each symdev. There might be another issue about the number of symdevs per meta and I've heard something about 2 to the powers of x.... so 2, 4, 8, 16, that kind of numbers, but I haven't been able to find any white papers about that.

I see you're pretty new to the forums, so hereby I welcome you ! If you have the time, please introduce yourself in the Coffee Break.

xe2sdc · Answer

Yes Quincy, thank you. I was talking about 'small numbers'. But I agree, it's better to warn even on higher limits

xe2sdc · Answer

Quincy unfortunatly I don't remember the name of our other thread.. But I remember we talked a lot on this topic (metamember number vs performances vs protection vs number of drives in backend). Thank you

xe2sdc · Answer

The reason you found is exactly the reason for pushing toward 2, 4, 8 or 16 members, depending on your backend size

However as we already said, it's simply a suggestion. Feel free to choose any metavolume members, as long as you don't reuse same physical drives

Quincy561 · Answer

Power of twos fit well into the DA/Disk layout.

emcuser123 · Answer

Thanks for the explaination.My understanding too is that as long as there is no overlap on the same physical disk, number should not matter.But I have heard exactly what you have about the using only 2, 4, 8, 16 members in the Meta and am curious to find where that is coming from. I didn't find anything in Black and White on that rule either. The only reason that I could think of is that using those numbers maybe provides some sort of balance across the DA's but I do not have any explaination of how it would do that.

RRR · Answer

That's exactly what I had in mind.If your Symm is using all physical disks with about the same load, you should be ok as the DA's and disks balance themselves this way.... You know what I mean. We're on the same wavelength.

Quincy561 · Answer

I would suggest not making the member count too large, like 250 members might be too large to really be able to get good performance.

RRR · Answer

You're welcome

emcuser123 · Answer

Thank you All for the Responses.

RRR · Answer

emcuser123,are you satisfied with our answers ?

Quincy561 · Answer

If you made a 250 member meta with 3+1 RAID5 and didn't share any disks, that would be a meta across 1,000 disks. To have 1 IO queued per disk on average, you would need to have 1,000 IOs queued to the meta, and that is assuming a perfect distribution.

emcuser123 · Answer

Quincy,Explaination of that statement would be really helpful.

Symmetrix

How many Hypers in a Meta Device

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