Information About Disk Mirroring - Cisco ASR 9000 Series User Configuration Manual

Information About Disk Mirroring

The primary partition on the secondary storage device must be large enough to contain all data on the
Note
primary boot device. This can be an issue if the primary boot device has not yet been partitioned. For
example, in the situation where both the primary boot device and the secondary storage device are 1 GB
in size, the primary boot device contains 950 MB of data, and the secondary storage device is already
partitioned to 800 MB in the primary partition and 200 MB in the secondary partition. In such a case, the
950 MB of data from the primary boot device does not fit on the secondary storage device because of the
partition. Such a configuration is rejected and an error is displayed. You need to replace the secondary
storage device with a higher capacity device. For information about disk partition sizes, see Related Topics.
Note Although compactflash: can be used as the secondary device on a Performance Route Processor (PRP–2),
there is an issue with the ROM Monitor not being able to boot the minimum boot image (MBI) from the
secondary device if the device is not disk0: or disk1:. In such a situation, you would need to go into
ROMMON mode and boot the PRP-2 manually using the MBI on the compactflash:.
Related Topics
Information About Disk Mirroring, on page 76
Information About Disk Mirroring
The route switch processor (RSP) card has a primary storage device that is used to store installation packages
and configuration files. This primary storage device is referred to as the primary boot device and is essential
for booting the RSP and its normal operation.
Disk mirroring replicates the critical data on the primary boot device onto another storage device on the same
RSP, henceforth referred to as the secondary device. If the primary boot device fails, applications continue
to be serviced transparently by the secondary device, thereby avoiding a switchover to the standby RSP. The
failed primary storage device can be replaced or repaired without disruption of service.
Disk mirroring should only mirror critical data on the primary boot device onto a secondary storage device
and not any noncritical data such as logging data. To separate critical data from noncritical data, the disk
devices need to be partitioned. Disk0: is partitioned to disk0: and disk0a:; disk1: is partitioned to disk1: and
disk1a:. Disk0: and disk1: are used for critical data, whereas disk0a: and disk1a: are used for logging data
and other noncritical data. Before you can configure disk mirroring on the RSP, you must have partitioned
the secondary storage device. The sizes of disk partitions are related to the total disk size, and are provided
in Table 12: Size of Disk Partitions in Relation to Size of Disk, on page
Table 12: Size of Disk Partitions in Relation to Size of Disk
Size of Disk
less than 900 MB
900 MB to 1.5 GB
1.5 GB to 3 GB
Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide, Release 5.1.x
76
Primary Partition Percentage
Partitioning not supported
80%
60%
Configuring Disk Mirroring
76.
Secondary Partition Percentage
Partitioning not supported
20%
40%