HP XP P9500 Storage - Manual (Page 57)

CAUTION:
•
If you change the processor blade ID for an LDEV, do this only when the I/O load is as low
as possible. Do not change the processor blade ID when the I/O load is high (for example:
during initial copy of Business Copy, Continuous Access Synchronous, or Continuous Access
Journal).
•
After you change the processor ID for an LDEV, wait more than 30 minutes before you try to
change it again for the same LDEV.
•
When you change the processor blade ID for an LDEV, you should use Performance Monitor
before and after the change to check the load status of devices.
Using a system disk
A system disk is a special LDEV used in the storage system for specific purposes. A system disk is
not required in a storage system, but is recommended for buffering of the audit log. A system disk
should not be used for storing user data. After a system disk is created, the system knows what
types of information the system disk is used for and all appropriate information is automatically
sent to the system disk.
For example, when the system disk is used as an audit log buffer, you set parameters to enable
the audit log buffer. The Audit Log feature recognizes the LDEV number of the system disk and then
accesses it as a buffer. The system disk must have sufficient capacity to accommodate the audit
log buffer. See Hitachi Audit Log User Guide for more information about how to enable the audit
log buffer.
To designate the system disk as the buffer area for audit logs, do one of the following:
•
In the Audit Log Setting window, set Audit Log Buffer to Enable.
•
Set system option mode (SOM) 676 to ON.
You can create a system disk on either a mainframe or an open system. To create a system disk,
you create an LDEV and then designate it as a system disk in the Create LDEVs wizard (see
“Creating
an LDEV” (page 48) ). The system disk designation prevents other storage system structures from
accessing it. It is not available to hosts, or a command device, pool volume, journal, and so on.
The system disk is part of one parity group. When an LDEV is defined as a system disk, the LDEV
cannot be allocated to a port.
The buffering area capacity for the audit log buffer is: 130 MB. Therefore, before using the audit
log, make sure to prepare the system disk to have at minimum the above mentioned free capacity
in the volume. The size of the system disk could be 1 GB if you want some spare capacity, or as
large as 15 GB to accommodate the amount of system information that could be stored on it.
If you find you do not need a system disk, you can delete the system disk and convert the volume
to free space (see
“Deleting an LDEV (converting to free space)” (page 53) ).
System disk rules, restrictions, and guidelines
Rules
•
The minimum size of the system disk should be 130 MB in order to accommodate audit log
buffer information.
•
The LDKC:CU:LDEV number assigned to the system disk should be distinguishable from the
one for a normal volume.
•
Use the Delete LDEVs function to delete the system disk.
Using a system disk 57