Dell EMC Unity: How to expand a Pool with Compression-enabled LUNs (User Correctable)
Summary: The article describes the requirements for expanding a storage pool which contains compressed LUNs, some of the conditions which may get in the way of the expansion, and how to work around them. ...
This article applies to
This article does not apply to
This article is not tied to any specific product.
Not all product versions are identified in this article.
Instructions
Dell EMC Unity Compression is supported on All Flash Pools created on Dell EMC Unity Hybrid Flash systems or Dell EMC Unity All Flash systems, which are running on revision 4.1 and later.
When expanding an All Flash Pool benefiting from compressions savings, the expansion must be made using compatible drives;
If compression is disabled, the previously compressed LUNs may still hold compressed segments (and therefore still show compression savings) until there are IO operations on those segments. In that case, expanding an All Flash Pool with SAS or NL-SAS drives would still fail, until the savings are down to 0.
When expanding an All Flash Pool benefiting from compressions savings, the expansion must be made using compatible drives;
- A Pool containing SAS Flash 2 or SAS Flash 3 drives can be expanded by adding more SAS Flash 2 or SAS Flash 3 drives.
- A Pool containing SAS Flash 4 drives can only be expanded using SAS Flash 4 drives.
- An All Flash Pool cannot be expanded with SAS or NL-SAS drives, while there are still compression savings within the pool.
If compression is disabled, the previously compressed LUNs may still hold compressed segments (and therefore still show compression savings) until there are IO operations on those segments. In that case, expanding an All Flash Pool with SAS or NL-SAS drives would still fail, until the savings are down to 0.
- How do I check the current compression savings on a Pool / LUN?
- From Unisphere GUI, under Storage > Pools, go to the Pool Properties of the relevant pool, and navigate to the Usage tab. You'll see the Compression Savings value.
Similarly for a LUN, under Storage > Block > LUNs go to the LUN Properties of the relevant LUN, you'll find the Compression Savings under the General tab.
- From UEMCLI:
uemcli -u user -p password /stor/config/pool show -detail
and uemcli -u user -p password /stor/prov/luns/lun show -detail
You'll see Inline compression space saved and Compression Percent values in both commands' outputs.
and uemcli -u user -p password /stor/prov/luns/lun show -detail
You'll see Inline compression space saved and Compression Percent values in both commands' outputs.
- How do I bring the compression savings of a LUN to 0, so that I'm able to expand an All Flash Pool with SAS or NL-SAS drives?
You can use LUN Move to relocate the LUN(s) to a different pool, or within the same Pool with compression disabled.
Additional Information
- For more details about compression, refer to the Unity Compression Overview document.
Affected Products
Dell EMC Unity FamilyProducts
Dell EMC Unity FamilyArticle Properties
Article Number: 000022829
Article Type: How To
Last Modified: 30 May 2024
Version: 3
Find answers to your questions from other Dell users
Support Services
Check if your device is covered by Support Services.