HP StorageWorks XP Remote Web Console Software - Manual (Page 66)

The maximum number of pairs you can create is restricted. Use the number of cylinders and bitmap
areas to calculate the maximum number of pairs that can be created in the storage system.
•
The type of difference management (track or cylinder):
The differential data between P-VOL and S-VOL is stored in units of tracks or cylinders.
CAUTION: You may specify the type of difference management when you create a pair
with the Add Pair dialog box. If an XP24000/XP20000 Disk Array is connected with an
XP12000/XP10000 Disk Array or an XP1024/XP128 Disk Array, the type of difference
management is applied as it is when you specify the unit. If an XP24000/XP20000 Disk Array
is connected with an XP12000/XP10000 Disk Array or XP1024/XP128 Disk Array, the
maximum number of pairs that you can create is the lesser number by comparing both numbers.
If the type of difference management is set to Auto, Track, or Cylinder will be set automatically
according to the number of cylinders of a volume that a pair will be created with. If VLL has
been used, the number of cylinders that you set with VLL software is applied. If the volume
that you want to create a pair with has 10,019 or more cylinders, Cylinder will be set. If the
volume has less than 10,019 cylinders, Track will be set.
If an XP24000/XP20000 Disk Array is connected with an XP12000/XP10000 Disk Array
or XP1024/XP128 Disk Array, the type of difference management that you can specify
depends on whether or not you use the Remote Web Console or Business Continuity Manager.
◦ Remote Web Console: Auto, Track, and Cylinder can be specified.
◦ Business Continuity Manager: Track and Cylinder can be specified. If you specified
nothing, the type of difference management will be Cylinder.
•
The number of cylinders:
The number of cylinders depends on the capacity of the volumes (the number of cylinders set
by VLL, if you set the VLL feature) used for the pairs. Both the MCU and RCU are restricted.
•
The number of bitmap areas:
To calculate the number of bitmap areas in each volume:
The number of bitmap areas = ( ((Number of cylinders x 15) / 122,752) )
The ... symbols around a value indicate that the value should be rounded up to the next
integer.
122,752 is the amount of differential data per bitmap area. The differential data is measured
in bits. If you are managing the differential data by cylinder, use the number of the cylinders
instead of the number which is derived from number of cylinders x 15 to calculate the number
of bitmap areas.
•
The maximum number of pairs that can be created:
The number of bitmap areas you can use in storage system depends on the number of shared
memories you add to storage system.
“Relationship between the Additional Shared Memory
and the Number of Usable Bitmap Areas of Storage System” (page 66) shows the relationship
between the number of shared memories and the number of usable bitmap areas of storage
system.
Table 25 Relationship between the Additional Shared Memory and the Number of Usable
Bitmap Areas of Storage System
Number of Usable Bitmap Areas of Storage System Additional Shared Memory for TrueCopy for Mainframe
0 No additional shared memory for TrueCopy for
Mainframe
7,424 Additional shared memory for TrueCopy for Mainframe
is installed
66 Preparing for TrueCopy for Mainframe Operations