Hi everyone,

Would enabling host_unmap on a V7000 Gen3/FS7200 (code 8.3.1.6) be disruptive to its front-end SVC (8.2.14)?
Same question for such FS7200, but connected directly to ESXi server, would it cause any trouble to LUN visibility or I/O for this ESXi?

Thank you in advance for any thoughts.

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Michał Tomanek
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Hi!

We had to change that option one or two years ago on our V5030 systems.  If I remember correctly, we then had both of them on 8.2.x microcode.   And if I remember the change was transparent for the SVC.

However, we disabled scsi_unmap, as it caused performance problems on the V5030 when deleting larger storage volumes on the SVC side.  SVC (whith backend_unmap on) sends unmap to the V5000s when a volume is deleted there and the V5000 in turn nulls the blocks, which caused in our case a lot of IOs.

If I remember correctly we were informed in the IBM call back then, that this would not be a recommended configuration for our setup, and unless we require it.

If you are interested, I can see if I can find the details.


Best regards,
  Alexander

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Alexander Reichle-Schmehl
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Hi Michał,

that specific configuration change conducted on back-end storage behind SVC is not disruptive,
neither does it impact LUN visibility. 

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Christian Schroeder
IBM SpecV Storage Support with Passion
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To close the loop:
neither enabling nor disabling SCSI UNMAP is a disruptive task.

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Christian Schroeder
IBM SpecV Storage Support with Passion
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Original Message:
Sent: Tue February 08, 2022 05:15 AM
From: Christian Schroeder
Subject: Enabling/disabling SCSI UNMAP disruptive?

Hi Michał,

that specific configuration change conducted on back-end storage behind SVC is not disruptive,
neither does it impact LUN visibility. 

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Christian Schroeder
IBM SpecV Storage Support with Passion
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Thank you @Christian Schroeder 

@Alexander Reichle-Schmehl Thank you as well.

​​

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Michał Tomanek
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Original Message:
Sent: Wed February 16, 2022 10:26 AM
From: Christian Schroeder
Subject: Enabling/disabling SCSI UNMAP disruptive?

To close the loop:
neither enabling nor disabling SCSI UNMAP is a disruptive task.

------------------------------
Christian Schroeder
IBM SpecV Storage Support with Passion
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Original Message:
Sent: Tue February 08, 2022 05:15 AM
From: Christian Schroeder
Subject: Enabling/disabling SCSI UNMAP disruptive?

Hi Michał,

that specific configuration change conducted on back-end storage behind SVC is not disruptive,
neither does it impact LUN visibility. 

------------------------------
Christian Schroeder
IBM SpecV Storage Support with Passion