Dell Unity: Automatic shrink is not activated even though there is enough free space (User Correctable)
Summary: Automatic shrink is not activated even though there is enough free space in the file system after deleting data.
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Symptoms
Automatic shrink is not activated even though there is enough free space in the file system after deleting data.
Cause
The requirements for Auto Shrink to work are different for Unity OE 4.4 and older code compared with Unity OE 4.5 and newer code.
For Unity OE 4.5 and above, it is determined by the Low Watermark value associated with the file system size and the number of shrinkable blocks in the file system that is monitored periodically.
The conditions under which Auto Shrink works are described in the "Dell EMC Unity: NAS Capabilities" documentation. See excerpt below.
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The system also monitors the file system utilization for a period prior to initiating an automatic shrink.
This avoids prematurely shrinking a file system, only to re-allocate the space when clients begin to write additional data.
The system monitors the shrinkable space of the file system every 1.5 hours.
It compares the amount of shrinkable space with the results of the previous check and updates a counter.
If the amount of shrinkable space is:
• Less than half of the previous check, this indicates the usage has increased significantly
o Action: Reset the counter back to 0
• More than half of the previous check, this indicates the usage has increased slightly
o Action: Decrement the counter by 1
• The same or has grown compared to the previous check, this indicates usage is staying the same or decreasing
o Action: Increment the counter by 1
Once the counter reaches 5, an automatic shrink is initiated.
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For Unity OE 4.5 and above, it is determined by the Low Watermark value associated with the file system size and the number of shrinkable blocks in the file system that is monitored periodically.
The conditions under which Auto Shrink works are described in the "Dell EMC Unity: NAS Capabilities" documentation. See excerpt below.
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The system also monitors the file system utilization for a period prior to initiating an automatic shrink.
This avoids prematurely shrinking a file system, only to re-allocate the space when clients begin to write additional data.
The system monitors the shrinkable space of the file system every 1.5 hours.
It compares the amount of shrinkable space with the results of the previous check and updates a counter.
If the amount of shrinkable space is:
• Less than half of the previous check, this indicates the usage has increased significantly
o Action: Reset the counter back to 0
• More than half of the previous check, this indicates the usage has increased slightly
o Action: Decrement the counter by 1
• The same or has grown compared to the previous check, this indicates usage is staying the same or decreasing
o Action: Increment the counter by 1
Once the counter reaches 5, an automatic shrink is initiated.
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Resolution
If free space is checked every 1.5 hours, automatic shrink will not work unless the free space is the same or lower than the previous check for five consecutive times (7.5 hours).
If automatic shrinking does not proceed, it is recommended to either intentionally match the above conditions or attempt manual shrinking.
If automatic shrinking does not proceed, it is recommended to either intentionally match the above conditions or attempt manual shrinking.
Affected Products
Dell Unity 300, Dell EMC Unity 300F, Dell EMC Unity 350F, Dell EMC Unity 400, Dell EMC Unity 400F, Dell EMC Unity 450F, Dell EMC Unity 500, Dell EMC Unity 500F, Dell EMC Unity 550F, Dell EMC Unity 600Products
Dell EMC Unity XT 380, Dell EMC Unity XT 380F, Dell EMC Unity XT 480, Dell EMC Unity XT 480F, Dell EMC Unity 600F, Dell EMC Unity 650F, Dell EMC Unity XT 680, Dell EMC Unity XT 680F, Dell EMC Unity XT 880, Dell EMC Unity XT 880F
, Dell EMC Unity Family |Dell EMC Unity All Flash, Dell EMC Unity Family, Dell EMC Unity Hybrid, Dell EMC UnityVSA Professional Edition/Unity Cloud Edition
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Article Properties
Article Number: 000191245
Article Type: Solution
Last Modified: 14 Nov 2024
Version: 3
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