FUJITSU CentricStor V3.1D - Manual (Page 71)

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Selected system administrator activities Dual Save
The specification of whether a logical volume group is defined as “FLOATING” or with cache
residence in a particular cache is made in the “Location” field when the logical volume group
is defined (see
section “Logical Volume Groups” on page 173 ).
The settings for the cache file system can be altered later at any time.
4.3 Dual Save
4.3.1 General
Dual Save (see page 50 ) is an optional system function which must be purchased
separately from the CentricStor basic configuration. It is released by the service engineer
by means of a key disk.
In order to use the Dual Save function, you must have at least two physical volume groups
(see
section “Partitioning on the basis of volume groups” on page 63 ).
If this prerequisite is fulfilled, the Dual Save function will cause each logical volume to be
duplicated in two different physical volume groups. If you have two robots installed at
different locations, you can enhance data security even further.
If a Dual-Save library should fail completely, logical volumes with the status “dirty”
cannot be saved to tape. They remain in the cache without being saved.
Only when the library is once more in the normal status (e.g. after a repair) are the
dirty volumes saved to tape.
If the failure of the library lasts for a long time, more and more volumes are placed
in the “dirty” status until CentricStor ultimately becomes inoperable.
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