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EMC Unity Disk Types: What happens...?

Hi all

Another time me I do have some questions related to disks and what happens within a pool (hybrid).

We do have a Hybrid EMC Unity with 3 disk types:

6x SAS 600 GB 10 K

11x SAS 600 GB 15 K

6x SAS 1.8 TB 10 K

I know that these are all the same tier type in theory becuase EMC segregates between NL-SAS, SAS and Flash but all of these are SAS.

My questions....

1) Can I put all these disks into a single pool anyhow?

1.1) Is there a logic which puts blocks on the faster 15K if they are "hot"? Or are they going to be treat like the other 10k?

1.2) What happens? 3x RAID Groups or 2x RAID Groups?

1.1) What defines the RAID Protection at the end? Amount of disks? Type of disks? Size? All of it?

1.3) What happens to the 15K disks are they going to be throttled down to 10k if they are in the same RAID Group with the 10 K or even the same pool? More or less the same thing with different disk sizes where the big disks are going to be cut down the the smallest in the group?

1.4) Are the 1.8 TB disk going to be shrinked in a pool with the 600 GB Disks? For sure they would if they are in the same RAID Group?

2) Based on the disk configuration up there what would be you prefered layout? My wishes are easy to handle environment with less complexity. On the other hand side how would you design the thing if you would like to have the best performance?

I know many questions...

Thanks and cheers

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5 Rhenium

Re: EMC Unity Disk Types: What happens...?

What code version is the Unity Running? If 4.2.x, then chek the new White Paper "docu85573_Dell-EMC-Unity--Dynamic-Pools---Overview.pdf" - there is a good explanation of how to configure Pools using Dynamic Pools, which does allow a mix of different SAS types in the same pool.

But a word of caution (as once you create the Pool you can't undo unless you destroy the Pool). Mixing different speed (rotational speed) will cause some uneven performance in the Pool when you access the 10K vs the 15K disks.

The Best practice guide shows the difference between the 10K and 15K for IOPS - 10K can do about 250 IOPS per disk and 15K can do about 350 IOPS per disk - when you access data on the 10K disks latency will be higher than data residing on the 15K disks. Ideally you would have two Pools - a 10K Pool and a 15K pool.


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