HP StorageWorks XP24000 Continuous Access Software User and Reference Guide, v01 (T5278-96002, June 2007)

• The number of bitmap areas:
To calculate the num b er of bitmap areas in each volume, use the following formulas:
• For OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L, OPEN-K
The number of b
itmap areas = ( ↑ ((Number of cylinders ×
15) ÷ 122,752) ↑ )
Note: 122,752 is the amount of differential data per bitmap area. The unit for the amount
of differential data is bits.
•For OPEN-V (wh
en
calculating the number of bitmap areas by using the number of cylinders
that is
calcul
ated
by using the formula mentioned earlier)
The number of bitmap areas = ( ↑ ((Number of cylinders × 15) ÷ 122,752) ↑ )
• For OPEN-V (when calculating the number of bitmap areas by using the number of cylinders
displayed in Remote Web Console windows)
The number of bitmap areas =
( ↑ (((Number of cylinders ÷ 4) × 15) ÷ 122,752) ↑ )
The ↑…↑ symbolsaroundavalueindicatethatthe valueshouldberounded up to thenext
integer.
• The maximum number of pairs that can be created:
The number of bitmap areas you can use in a storage system depends on the number of shared
memories yo
u
add to the storage system. Table 3 o n page 21 shows the relationship between the
additiona
l
shared mem ory and the number of usable bitmap areas of a storage system.
Table 3 Rel
ationship between the Additional Shared Memory and t he N umber of
Usable Bitmap Areas of a Storage System
Additional Shared Memory for Continuous
Access
Number of Usable Bitmap Areas of a Storage
System
No additional shared memory for Continuous
Access
0
Additional shared memory for Continuous Access
is
installed
7,424
Extension 1
16,384
Extension 2 32,768
Extension 3
44,256
Extension 4
65,536
If the calculated number of bitmap areas exceeds the total number of bitmap areas in the storage
system, the number of pairs that can be created will be limited.
To calculate the maximum number of pairs that you c an create:
The maximum number of pairs that you can create =
( ↓ (the total number of bitmap areas in the
stor
age
system ÷ Number of bitmap areas) ↓ )
The ↓…↓ symbols around a value indicate that the value should be rounded down to the
former integer .
Note: The maximum number of p a irs that you can create cannot exceed 32,768.
Caution: The bitmap areas that are used for Continuous Access are shared with H P StorageWorks
Continuous Access Journal Software. If you use both Continuous Access and Continuous Access
Journal, usethe totalnumberofbothpairs. Also, if youuse thesame volumewithContinuous
Access and Continuous Access Journal, use the total number of both pairs regardless of whether
the
volume is a P-VOL or S-VOL.
• The unit of Difference Ma n agement (track or cylinder):
The differential data between a P-VOL and S-VOL is stored in units o f tracks or cylinders.
Caution: You may specify the unit of Difference M anagement when you crea te a pair with the
Paircreate dialog box (see “Creating Continuous Access Pairs” on page 105) . If an HP XP24000
Disk Array is connected with an HP XP12000 Disk Array, the unit of D ifference Management
is applied as it is when you specify the unit. If an HP XP24000 Disk Array is connected with
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