Hello,

Maybe a short introduction: I inherited an IBM FlashSystem 5000 from my predecessor. Never worked with IBM before.

On this FlashSystem there is a "Data Reduction Pool" with 31 TiB capacity, and inside this pool there is a deduplicated volume with 20 TiB capacity. This Volume is mapped to an ESXi cluster.

Problem is, the volume only has 450 GiB of 20 TiB space left in ESXi, but when i try to expand the volume on the storage, its greyed out with the information that this action is not available for this type of volume. After reading the docs i found out, that there is a feature called "autoexpand" which will - as far as i understood - automatically expand the volume before it gets full, and therefore it has a so called contingency capacity.

But i found nothing about how to see how big this contingency capacity is and when the autoexpand will happen? In fact i would like to change the settings, so that the ESXi sees a volume with 25 TiB of capacity. Is there a way to do this?

Thanks! And sorry if this is obvious - I couldn't find the right solution in the docs.

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Florian Roth
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Hi Florian,

To say something about your question on "autoexpand" in short and simple ("short and simple" is not lossless): maybe you missed/misunderstood the explanation in the docs. This function works in the boundaries of the "provisioned capacity" which is 31 TiB in your case. "autoexpand" will not expand beyond the 31 TiB. So this function will not help you. Sorry. 

To investigate further: can you please show the ssh/cli outputs of "lssystem", "lsvdisk <name_of_the_volume>" and "lspool <name_of_the_pool_the_volume_is_in". Which type of "hard/flash disk" is in the pool ("lsdrive" will be enough)?

Kind regards

Ralf 

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Ralf Lichtenstein
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At least one correction: "This function works in the boundaries of the "provisioned capacity" which is 31 TiB in your case. " - i mean "This function works in the boundaries of the volumes  "provisioned capacity" which is 20 TiB in your case."

Sorry for that.

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Ralf Lichtenstein
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Hi Florian,

Just to confirm what Ralf has said - Autoexpand is a legacy feature (when thin provisioining was new) which was about auto expanding the thin capacity into the provisioned capacity.  Largely it should always be on by default and wont' change the presented volume size to a host.

For that you need expand volume - there are restrictions on what kind of volumes can be expanded.  See the documentation here: https://www.ibm.com/docs/en/flashsystem-9x00/8.7.x?topic=vc-expandvdisksize

For your use case you want to change the provisioned size (or -size) and not the -rsize (which is the real size the volume takes on disk, which autoexpand does for you).

I hope this helps, if not, please come back with more detail on the vdisk (volume) you are trying to expand.

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Evelyn Perez
IBM Senior Technical Staff Member
IBM Storage Virtualize Software Architect for SVC and FlashSystem
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Hi Ralf, Hi Evelyn,

Thanks for your answers! The tip with using the CLI and the -size parameter did point me in the right direction.

Solved.

Thanks!

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Florian Roth
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Original Message:
Sent: Thu January 09, 2025 06:55 AM
From: Evelyn Perez
Subject: FlashSystem 5000 - expand volume

Hi Florian,

Just to confirm what Ralf has said - Autoexpand is a legacy feature (when thin provisioining was new) which was about auto expanding the thin capacity into the provisioned capacity.  Largely it should always be on by default and wont' change the presented volume size to a host.

For that you need expand volume - there are restrictions on what kind of volumes can be expanded.  See the documentation here: https://www.ibm.com/docs/en/flashsystem-9x00/8.7.x?topic=vc-expandvdisksize

For your use case you want to change the provisioned size (or -size) and not the -rsize (which is the real size the volume takes on disk, which autoexpand does for you).

I hope this helps, if not, please come back with more detail on the vdisk (volume) you are trying to expand.

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Evelyn Perez
IBM Senior Technical Staff Member
IBM Storage Virtualize Software Architect for SVC and FlashSystem
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