Dell PowerVault MD3820f - Manual (Page 87)

enables you to limit the automatic growth of a virtual disk to an amount less than the defined virtual
capacity.
NOTE: Since less than full capacity is allocated when you create a thin virtual disk, insufficient free
capacity may exist when certain operations are performed, such as snapshot images and snapshot
virtual disks. If this occurs, an alert threshold warning is displayed.
Thin Virtual Disk Requirements And Limitations
The following table provides the minimum and maximum capacity requirements applicable to thin virtual
disks.
Table 3. Minimum and Maximum Capacity Requirements
Capacity Types Size
Virtual capacity
Minimum 32 MB
Maximum 63 TB
Physical capacity
Minimum 4 GB
Maximum 64 TB
The following limitations apply to thin virtual disks:
• The segment size of a thin virtual disk cannot be changed.
• The pre-read consistency check for a thin virtual disk cannot be enabled.
• A thin virtual disk cannot serve as the target virtual disk in a Virtual Disk Copy.
• A thin virtual disk cannot be used in a Snapshot (Legacy) operation.
• A thin virtual disk cannot be used in a Remote Replication (Legacy) operation.
Thin Volume Attributes
When you create a thin virtual disk from free capacity in an existing disk pool, you can manually set disk
attributes or allow MD Storage Manager to assign default attributes. The following manual attributes are
available:
• Preferred Capacity — Sets the initial physical capacity of the virtual disk (MB, GB or TB). Preferred
capacity in a disk pool is allocated in 4 GB increments. If you specify a capacity amount that is not a
multiple of 4 GB, MD Storage Manager assigns a 4 GB multiple and assigns the remainder as unused. If
space exists that is not a 4 GB multiple, you can use it to increase the size of the thin virtual disk. To
increase the size of the thin virtual disk, select Storage → Virtual Disk → Increase Capacity.
• Repository Expansion Policy — Select either Automatic or Manual to indicate whether MD Storage
Manager must automatically expand physical capacity thresholds. If you select Automatic, enter a
Maximum Expansion Capacity value that triggers automatic capacity expansion. The MD Storage
Manager expands the preferred capacity in increments of 4 GB until it reaches the specified capacity.
If you select Manual, automatic expansion does not occur and an alert is displayed when the Warning
Threshold value percentage is reached.
• Warning Threshold — When consumed capacity reaches the specified percentage, MD Storage
Manager sends an E-mail or SNMP alert.
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