Disks (sometimes also called drives) provide the basic unit of storage for storage systems running Data ONTAP that use native storage shelves. Understanding how Data ONTAP uses and classifies disks will help you manage your storage more effectively.
How Data ONTAP reports disk types
Data ONTAP associates a type with every disk. Data ONTAP reports some disk types differently than the industry standards; you should understand how Data ONTAP disk types map to industry standards to avoid confusion.
Methods of calculating aggregate and system capacity
You use the physical and usable capacity of the drives you employ in your storage systems to ensure that your storage architecture conforms to the overall system capacity limits and the size limits of your aggregates.
Disk speeds supported by Data ONTAP
For hard disk drives, which use rotating media, speed is measured in revolutions per minute (RPM). Faster drives provide more input/output operations per second (IOPS) and faster response time.
Drive name formats
When a node is part of a functioning cluster, the drives it is connected to are accessible using a simple, consistent drive name format. The drive name is independent of what nodes the drive is physically connected to and from which node you are accessing the drive.
Pre-cluster drive name formats
During steady-state operations, drive names are independent of their physical connection and unaffected by the node from which they are viewed. However, during system boot, before a node has joined a cluster, and if certain system components become unavailable, drive names revert to the format used before Data ONTAP 8.3, the pre-cluster format.
Understanding RAID drive types
Data ONTAP classifies drives (or, for partitioned drives, partitions) as one of four types for RAID: data, hot spare, parity, or dParity. You manage disks differently depending on whether they are spare or being used in an aggregate.
How disk sanitization works
Disk sanitization is the process of physically obliterating data by overwriting disks or SSDs with specified byte patterns or random data so that recovery of the original data becomes impossible. You use the sanitization process to ensure that no one can recover the data on the disks. This functionality is available through the nodeshell.
How Data ONTAP monitors disk performance and health
Data ONTAP continually monitors disks to assess their performance and health. When Data ONTAP encounters certain errors or behaviors from a disk, it takes the disk offline temporarily or takes the disk out of service to run further tests.
How you use SSDs to increase storage performance
Solid-state drives (SSDs) are flash media-based storage devices that provide better overall performance than hard disk drives (HDDs), which are mechanical devices using rotating media. You should understand how Data ONTAP manages SSDs and the capability differences between SSDs and HDDs.
Understanding root-data partitioning
Some platform models use partioning to enable the root aggregate to use less space, leaving more space for the data aggregate and improving storage utilization. Root-data partitioning, also called shared drives, changes the way you view and administer your disks and aggregates.
Adding disks to a node
You add disks to a node to increase the number of hot spares, to add space to an aggregate, or to replace disks.
Replacing a self-encrypting disk
Replacing a self-encrypting disk (SED) is similar to replacing a regular disk, except that there are some extra steps you must take to reenable Storage Encryption after you replace the disk.
Removing disks from a node
How you remove a disk from a node depends how the disk is being used. By using the correct procedure, you can prevent unwanted AutoSupport notifications from being generated and ensure that the disk functions correctly if it is reused in another node.