Aiyappa
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Unity Drive Selection

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Is there a way we can manually pick drives to be part of a Storage group ? in other words ,  how do we avoid Systems drives becoming part of a storage pool ?

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8 Krypton

Re: Unity Drive Selection

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Aiyappa,

I have a hybrid Unity in my lab.  This is an interesting question so I deleted my pools and tried recreating them from scratch.  If I create a new pool or expand a pool, I can confirm the behavior is it selects the non-system drives first. 

After selecting the tiers, when you go to the step to select disks, it doesn't let you specify exact disks, but you can tell when it's adding system drives based on the "Usable Capacity." In the example below, if I select 5 of 11 disks, 2.1TB, that doesn't include system drives.  Selecting 10 of 11, 3.8TB includes system drives.  The system drives in that case are only providing 1.7TB of usable capacity, vs the 3.8 when using the non-system drives.

I tried this a few different ways, and bottom line, system drives always go last.

It would be nice if more information was provided at the point you are adding system drives, but I think that may go against the style goal of simplicity with this product.

AddPool.jpg

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8 Krypton

Re: Unity Drive Selection

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you can't select drives but system drives will be used last

8 Krypton

Re: Unity Drive Selection

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You could use the CLI commands to manually assign specific disks to a Pool. See the CLI guide on page 250:

Configure a storage pool.

Format

/stor/config/pool create

-drivesNumber (physical deployments only)

Specify the disk numbers, separated by commas, from the selected disk groups to use in the storage pool. If this option is specified when -storProfile is not specified, the operation may fail when the -drivesNumber value does not match the default RAID configuration for each drive type in the selected disk group

glen

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Aiyappa
6 Indium

Re: Unity Drive Selection

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Hello Glen,

The -DrivesNumber switch is to specify # of drives in a Group . It does not all you to pick a specific Drive. 

Hello Rainer_EMC,

is there a document/example  which says/shows  that the System drives will be picked up last ?

Regards,

Aiyappa

8 Krypton

Re: Unity Drive Selection

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Aiyappa,

I have a hybrid Unity in my lab.  This is an interesting question so I deleted my pools and tried recreating them from scratch.  If I create a new pool or expand a pool, I can confirm the behavior is it selects the non-system drives first. 

After selecting the tiers, when you go to the step to select disks, it doesn't let you specify exact disks, but you can tell when it's adding system drives based on the "Usable Capacity." In the example below, if I select 5 of 11 disks, 2.1TB, that doesn't include system drives.  Selecting 10 of 11, 3.8TB includes system drives.  The system drives in that case are only providing 1.7TB of usable capacity, vs the 3.8 when using the non-system drives.

I tried this a few different ways, and bottom line, system drives always go last.

It would be nice if more information was provided at the point you are adding system drives, but I think that may go against the style goal of simplicity with this product.

AddPool.jpg

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Aiyappa
6 Indium

Re: Unity Drive Selection

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Thanks for the Information Storagetallk , Appreciate It.

Regards,

Aiyappa

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8 Krypton

Re: Unity Drive Selection

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Well summarized, storagetalk.  I also checked the documents and can see some reference in the Unity Best Practices white page :

https://support.emc.com/docu69891_Unity:-Best-Practices-Guide.pdf?language=en_US

Page 11 says:

Due to the capacity difference of the system drives, Unity will not add them to storage pools until all other non-spare drives of the same type have been used, which is confirmed by your tests as well.

Also to note : For Unity All-Flash, there are no restrictions on using the system drives in storage pools. (again this will be picked last due to size difference)

Of course, the drives can be physically swapped anytime if a customer is dead set about the drive number/locations.

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