HP StorageWorks XP Remote Web Console Software - Manual (Page 17)

management. The type that you can specify depends on whether you use the XP Remote Web
Console or XP RAID Manager.
◦ XP Remote Web Console: Auto, Track, and Cylinder can be specified.
◦ XP RAID Manager: Track and Cylinder can be specified. If you specified nothing, the
type of difference management will be Track.
CAUTION: If the type of difference management is set to Auto, then Track or Cylinder will
be set automatically according to the number of cylinders of a volume that a pair is created
with. If custom volume size (CVS) has been used, the number of cylinders that you set with
CVS 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.
S-VOL write option
XP Continuous Access provides an S-VOL write option that enables write access to the S-VOL of a
split XP Continuous Access pair. The S-VOL write option can be selected during the pairsplit-r
operation and applies only to the selected pairs. The S-VOL write option can be accessed only
when you are connected to the MCU. When you resync a split XP Continuous Access pair that
has the S-VOL write option enabled, the RCU sends the S-VOL cylinder bitmap to the MCU, and
the MCU merges the P-VOL and S-VOL bitmaps to determine which cylinders are out of sync. This
ensures proper resynchronization of the pair.
XP Continuous Access Asynchronous recordset operations
XP Continuous Access Asynchronous recordsets contain P-VOL updates and associated control
information, including sequence number of the P-VOL update, which enables the RCU to maintain
update consistency of S-VOLs. XP Continuous Access Recordset operations include:
•
Creating and storing recordsets at the MCU
•
“Sending recordsets to the RCU” (page 18)
•
Storing recordsets at the RCU
•
“Selecting and settling recordsets at the RCU” (page 18)
•
“Types of recordsets” (page 19)
•
Inflow control of recordsets
Creating and storing recordsets at the MCU
When an MCU performs an update (host-requested write I/O) on a P-VOL, the MCU creates a
recordset containing the updated record, sequence number, record location (device, cylinder,
track, and record number), and record length. Recordsets are queued in cache storage of the MCU
and sent to the RCU independent of host I/O processes. The RCU utilizes sequence number
information in the recordsets to update S-VOLs in the same order as P-VOLs.
The sequence number indicates the number of recordsets the MCU created for each consistency
group. Recordset information, except for updated records, is stored and queued in an area of
cache known as sidefile cache (see
Inflow control of recordsets ).
XP Continuous Access Asynchronous recordset operations 17