User's Manual

HP StorageWorks File System Extender Software user guide 105
A duplicated medium is an exact copy of the original medium. An original medium and its copy have the
following characteristics:
same medium volume headers, including medium volume UUIDs
same Fast Recovery Information data on system volume and all data volumes
same data
same media types and capacities
different medium barcodes
IMPORTANT: When a medium duplicate is used to replace its original in the FSE implementation, the
barcode of its original must be used when the duplicate is put into the library.
How it works
An administrative job is started to duplicate a medium. A medium duplication process first requests FSE
disk buffer resources, allocates the original medium and then the target medium. If the prerequisites are
met, the medium duplication is started volume by volume. Once finished, the medium copy has the same
attributes and data as the original except for the medium barcode.
NOTE: To replace an original medium with its duplicate, you should label the duplicate medium with the
original barcode, remove the original medium, and use the duplicate instead.
When a medium copy is first used in place of the original, a warning is written to the fse.log file as the
FSE implementation recognizes that the medium for the particular barcode has been switched.
Typically, when you decide to duplicate a medium, for example for storing backup copies off-site, the
original medium is full and all its medium volumes are closed. If the medium is not yet full and still has
open volumes that are almost full, HP recommends that you first close all such volumes (as described in
Closing medium volumes” on page 120), and then start duplicating. This way you will not have to repeat
the duplicating procedure each time new data is migrated to the original medium.
If you are duplicating a medium that still has open volumes, the medium volumes are copied as is and are
left open on the target medium. Therefore, you have to repeat the duplication procedure every time new
data is migrated to the original medium in order to have an up-to-date medium copy. In such cases, you
can reuse the same target medium as described in ”Procedure for duplicating media” on page 105.
Note that while a medium duplication is in progress, no other job (migration or recall) can use the storage
space that was allocated in the FSE disk buffer. The migration jobs are resumed when the storage space is
freed, while recall jobs fail after the specified timeout.
Procedure for duplicating media
Before you start duplicating an FSE medium, you must ensure that the media duplication prerequisites are
met. Note that the most common reasons for media duplication failures are shortage of storage space in
the FSE disk buffer and mismatches in the medium characteristics.
Prerequisites
A target medium, which will hold a copy of the original data, must be of the same type as the original
medium.
The target medium must have sufficient capacity.
The FSE disk buffer must have enough free storage space for temporary data. The largest file system
assigned to the FSE disk buffer must have twice as much storage space as is the native capacity of the
FSE medium which will be duplicated. The following examples show the native media capacities and
the required file system sizes:
LTO 1 : 100 GiB * 2 = 200 GiB