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Storage : LUNs : Understanding LUNs : Guidelines for working with FlexVol volumes that contain LUNs
Guidelines for working with FlexVol volumes that contain LUNs
When you work with FlexVol volumes that contain LUNs, you must change the default settings for Snapshot copies. You can also optimize the LUN layout to simplify administration.
Snapshot copies are required for many optional features, such as the SnapMirror feature, SyncMirror feature, dump and restore, and ndmpcopy.
When you create a volume, Data ONTAP automatically performs the following:
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Reserves 20 percent of the space for Snapshot copies
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Schedules Snapshot copies
Because the internal scheduling mechanism for taking Snapshot copies within Data ONTAP does not ensure that the data within a LUN is in a consistent state, you should change these Snapshot copy settings by performing the following tasks:
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Turn off the automatic Snapshot copy schedule.
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Delete all existing Snapshot copies.
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Set the percentage of space reserved for Snapshot copies to zero.
You should use the following guidelines to create volumes that contain LUNs:
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Do not create any LUNs in the system’s root volume.
Data ONTAP uses this volume to administer the storage system. The default root volume is /vol/vol0.
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You should use a SAN volume to contain the LUN.
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You should ensure that no other files or directories exist in the volume that contains the LUN.
If this is not possible and you are storing LUNs and files in the same volume, you should use a separate qtree to contain the LUNs.
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If multiple hosts share the same volume, you should create a qtree on the volume to store all the LUNs for the same host.
This is a best practice that simplifies LUN administration and tracking.
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To simplify management, you should use naming conventions for LUNs and volumes that reflect their ownership or the way that they are used.
See the Data ONTAP 7-ModeStorage Management Guide for more information.
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Documentation: By Product Library: support.netapp.com/documentation/productsatoz/index.html

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