Siemens Network Hardware SM2 monitoring system Manual De Usuario

U3585-J-Z125-8-76

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Notes on SM2 operation

The product DRV (Dual Recording by Volume) can be used to keep double copies of disk
drives in the form of mirror images. This increases the availability factor for data stored on
the disks. Each write request made by DMS is sent to both disks, and each read request is
executed on the disk with the shortest access time available (shortest positioning path,
lowest queue length prior to the disk drive).

The duplicate of the disk has its own mnemonic device address, yet the same VSN as the
original disk. When interpreting the monitoring values, the consequences of this are the
following ones:

–

The VSN is duplicated in the CONFIGURATION table (with different mnemonic name
values), provided that DRV was in operation before SM2 started.

–

In the DEVICE report as well, a VSN can appear in duplicate (with monitoring values).

–

In Report 12 (percentage of device utilization per VSN), SM2R1 lists the monitored data
of both drives; in extreme cases utilization values of up to 200% may be the case.

It is not possible to determine load values for bus channels. On SR2000 systems, channels
0-F are always bus channels (see information on the CHANNEL report, page 227).

–

When the remote copy function SRDF (Symmetrix Remote Date Facility, see manual
SHC-OSD [22]) is used, the resulting remote copy times are counted with remaining
service time in the case of synchronous or semi-synchronous processing.

–

If the total hit rate is 100%, the device discount time is zero.