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Storage : Volumes : Understanding volumes : Understanding the root volume and the root aggregate
Understanding the root volume and the root aggregate
The storage system's root volume contains special directories and configuration files that help you administer the storage system. The root aggregate contains the root volume. Understanding the facts about the root volume and the root aggregate helps you manage them.
The following facts apply to the root volume:
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How the root volume is installed and whether you need to create it yourself depend on the storage system.
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For FAS systems and V-Series systems ordered with disk shelves, the root volume is a FlexVol volume that is installed at the factory.
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For a V-Series system that does not have a disk shelf, you install the root volume on the third-party storage.
For more information about setting up a V-Series system, see the Data ONTAP Software Setup Guide for 7-Mode.
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For systems running virtual storage, the Data ONTAP-v installation process creates a single aggregate by using all currently defined virtual disks and creates the root FlexVol volume in that aggregate.
For more information about system setup, see the Installation and Administration Guide that came with your Data ONTAP-v system.
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The default name for the root volume is /vol/vol0.
You can designate a different volume to be the new root volume. Starting in Data ONTAP 8.0.1, you can designate a 64-bit volume to be the new root volume.
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The root volume's fractional reserve must be 100%.
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A VM-aligned volume is not supported as a root volume.
The following facts apply to the root aggregate:
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Starting with Data ONTAP 8.1, new systems are shipped with the root volume in a 64-bit root aggregate.
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By default, the storage system is set up to use a hard disk drive (HDD) aggregate for the root aggregate.
When no HDDs are available, the system is set up to use a solid-state drive (SSD) aggregate for the root aggregate. If you want to change the root aggregate, you can choose either an HDD aggregate or an SSD aggregate to be the root aggregate (by using aggr options aggr_name root), provided that the corresponding type of disk drives is available on the system.
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A Flash Pool (an aggregate that contains both HDDs and SSDs) can be used as the root aggregate.
If you downgrade to Data ONTAP 8.1 or earlier with a Flash Pool configured as your root aggregate, your system will not boot.

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