Before we discuss space reservation in NetApp, here is a look at the logical representation of aggregate, volume and LUN.
The LUN is created within a volume. There can be more than one LUN within a volume.
When creating a LUN, you can reserve all the space required for the LUN or let the LUN consume capacity on need basis.
Scenario 1: Create 100GB LUN on 500GB volume with space reserved enabled. This immediately consumes 100GB capacity on the volume.
Scenario 2: Create 100GB LUN on 500GB volume with space reserved disabled. This creates a LUN of 100GB but doesn't consume the capacity on the volume. As data gets written to the LUN, the capacity is consumed.
NOTES:
1) LUN reservation is a property of the LUN and it is persistent across reboots, TO and GB.
2) There is a property on the volume called 'space gaurantee' or 'gaurantee'. When you create LUN with space reservation enabled then you should check the volume gaurantee settings as well. If volume gaurantee is none, then LUN space reservation might not actually work.
3) LUN space allocation is a feature that ensure the LUN follows the T10 SCSI standard. This standard requires that LUN remain online even when the LUN is full. If space allocation is disabled, then when the LUN is full (and it cant grow) it goes offline. However, if the space allocation option is enabled, then when the LUN if full (and it cant grow) it remain online. Hosts can read from the LUN but it cant write to the LUN.
4) LUN space allocation also enables storage to reclaim space automatically when the host deletes data.
https://library.netapp.com/ecmdocs/ECMP1368845/html/GUID-A926B796-9C0D-4935-A84A-D9BF291487A4.html
https://library.netapp.com/ecmdocs/ECMP1368845/html/GUID-93D78975-6911-4EF5-BA4E-80E64B922D09.html
The LUN is created within a volume. There can be more than one LUN within a volume.
When creating a LUN, you can reserve all the space required for the LUN or let the LUN consume capacity on need basis.Scenario 1: Create 100GB LUN on 500GB volume with space reserved enabled. This immediately consumes 100GB capacity on the volume.
Scenario 2: Create 100GB LUN on 500GB volume with space reserved disabled. This creates a LUN of 100GB but doesn't consume the capacity on the volume. As data gets written to the LUN, the capacity is consumed.
NOTES:
1) LUN reservation is a property of the LUN and it is persistent across reboots, TO and GB.
2) There is a property on the volume called 'space gaurantee' or 'gaurantee'. When you create LUN with space reservation enabled then you should check the volume gaurantee settings as well. If volume gaurantee is none, then LUN space reservation might not actually work.
3) LUN space allocation is a feature that ensure the LUN follows the T10 SCSI standard. This standard requires that LUN remain online even when the LUN is full. If space allocation is disabled, then when the LUN is full (and it cant grow) it goes offline. However, if the space allocation option is enabled, then when the LUN if full (and it cant grow) it remain online. Hosts can read from the LUN but it cant write to the LUN.
4) LUN space allocation also enables storage to reclaim space automatically when the host deletes data.
https://library.netapp.com/ecmdocs/ECMP1368845/html/GUID-A926B796-9C0D-4935-A84A-D9BF291487A4.html
https://library.netapp.com/ecmdocs/ECMP1368845/html/GUID-93D78975-6911-4EF5-BA4E-80E64B922D09.html
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