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Using nearline storage: Difference between revisions
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== Using nearline == <!--T:22--> | == Using nearline == <!--T:22--> | ||
The basic model for using nearline is that you put files there, and later you may access them, like a normal filesystem, except that reading the files may involve a significant pause. You may also remove files from nearline. It's important to realize that nearline files can be in several different states: | The basic model for using nearline is that you put files there, and later you may access them, like a normal filesystem, except that reading the files may involve a significant pause. You may also remove files from nearline. It's important to realize that nearline files can be in several different states: | ||
* immediately upon creation, the file is on disk, not tape | * immediately upon creation, the file is on disk, not tape. | ||
* after a period (on the order of a day), the system will copy the file to tape. At this stage, the file will be on both disk and tape; it will behave just like a disk file, unless you modify it. | * after a period (on the order of a day), the system will copy the file to tape. At this stage, the file will be on both disk and tape; it will behave just like a disk file, unless you modify it. | ||
* after a further period, the disk copy will be dropped, and the file will only be on tape (our policy is two tape copies: one local and one remote). At this point, the file will be slow to read, since content must be recalled from tape. | * after a further period, the disk copy will be dropped, and the file will only be on tape (our policy is two tape copies: one local and one remote). At this point, the file will be slow to read, since content must be recalled from tape. | ||