In IBM's terminology beginning with the System/360 disk and such devices featuring short access times were collectively called DASD. The IBM 2321 Data Cell is a DASD that used tape as its storage medium. See also history of IBM magnetic disk drives.
Additionally, CTA can be used to restore file or block data from cloud storage to an on premises, primary storage Unity XT array in a retrieval process known as recall for file and restore for block. And finally, CTA can be used to migrate file repositories between older storage arrays and a Unity array, as well as between cloud providers (Fig 1.). Currently the CTA integrates with the following cloud storage providers: Dell EMC Elastic Cloud Services (ECS), IBM Cloud Object Storage, Microsoft Azure, and AWS S3.
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When archiving block storage, the CTA operates as a policy engine, interfacing with the Unity XT array and identifying block snapshots that are assigned specific criteria which the CTA administrator defines (the Policies or Schedules mentioned above). Those snapshots are then archived to cloud storage (again, as defined in Policies and Schedules), and once the transfer finishes, the snapshot on the Unity XT array can be erased, reclaiming valuable storage capacity for your on-premises operations. To restore block data from the cloud through CTA, an administrator can utilize a target of block storage on the source array, or block storage on a new Unity XT array in any location.
For file tiering, CTA again acts as a policy engine, connecting to a Unity XT array and ascertaining which Policies and Schedules apply to which files. When those files are identified, the CTA creates a stub in the original location, and tiers the file to cloud storage. When a stub is read, the CTA will either recall the file to the local array or pass IO through to the file located in the cloud. For clients and end users, this process delivers a seamless experience, regardless of the origination of the file. The real benefit here is that the stub that CTA creates utilizes only 8KB of disk, versus the entire consumed capacity of the file itself that would exist. This is another great way to reclaim consumed capacity on the Unity XT array and utilize it for your more latency sensitive applications and operations that require storage in the data center. 2ff7e9595c
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