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CentricStor - Virtual Tape Library Procedures
2.6.2 Issuing a mount job from the host
Initial situation: The logical volume LV0005 is already located on the physical volume
PV0002.
Figure 14: Procedure for a mount job
A mount job is executed as follows:
1. The host issues a mount job for logical volume LV0005, which is then accepted by the
VLM.
The VLM does not know at this point what task is involved:
– read the volume or a part thereof
– append a file to the end of the volume
– overwrite the entire volume
2. The VLM checks its data maintenance to establish whether the logical volume LV0005
specified by the host is available and whether there is a corresponding free storage
space on the RAID system.
If the RAID system does not have enough free capacity at this point, the LRU (Least
Recently Used) procedure is employed to delete the oldest data from the RAID system.
If a sufficient number of old files cannot be deleted, the mount job is suspended (“Mount
queued”).
Logical volumes
Physical volumes
Tape drive
RAID
Robots
CentricStor
Host
VLM PLM
LV0000
LV0001 M
1
LV0004
LV0006 M
LV0007
LV0008
LV0009 M
LV0010 D
LV0011
PV0001
LV0004
LV0017
LV0027
LV0013
PV0002
LV0005
Data
LV0003
2
PV0000
LV0000
LV0001
LV0003
4
LV0027 LV0005
LV0013
PV0004
PV0002
LV0005
LV0002
LV0005
5
b
e
3
f
a
LV0005
Data
d
c
PV0000
PV0000
PV0012
PV0000
PV0000
PV0009
PV0008
PV0007
PV0006
PV0005
PV0004
PV0003
PV0001
PV0000
LV0000 LV0001
LV0003
LV0004 LV0017
PV0002
LV0061
LV0073