cc_staff
176
edits
Using nearline storage: Difference between revisions
Jump to navigation
Jump to search
m
→Using Nearline
m (→Using Nearline) |
m (→Using Nearline) |
||
| Line 17: | Line 17: | ||
== Using Nearline == | == Using Nearline == | ||
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. | 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 sevearl different states: | ||
* immediately upon creation, the file is on disk, not tape. this is mainly to avoid having to guess about when you're done putting the file into place. | |||
* 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'll 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. | |||
* when such a file is recalled, it returns to the second state. | |||
Thus, you may wish to inquire about the status of a Nearline file: | |||
lfs hsm_state ~/nearline/def-mine/user/somefile | lfs hsm_state ~/nearline/def-mine/user/somefile | ||
will report on the HSM status of the file | will report on the HSM status of the file. If you wish to ensure that the file is brought in from tape, you can also: | ||
lfs hsm_restore | lfs hsm_restore | ||