Guralp Systems CMG-DCM - Manual (Page 89)

Operator's guide
system log onto the disk. The system log is split up into time blocks in
the same way as the other data (see disk.recordinterval, below.)
Status blocks from digitizers are part of the GCF data, not part of the
log. To record these, you need to enable disk.recordas.gcf. If you also
enable disk.recordsplit (see below), each status stream will be
recorded in its own file.
disk.recordfrom.coalesce : The DM24 digitizer can be configured to
produce GCF blocks more quickly than normal. This may be done, for
example, to reduce the latency in data transmission. Blocks produced
this way may not all be full, so space will be wasted. You may also
experience problems with recording bandwidth.
Enabling this option makes the DCM build full GCF blocks from the
data it receives (a process known as re-blocking) before saving it to
disk. You should only need to enable this option if you are using the
low latency features of the DM24 digitizer. It is disabled by default.
Other disk options
disk.power : To save power, the on-board hard disk can be set to
power up only when required. If power consumption is an issue and
you expect the hard disk to be used only occasionally, you should set
this option to automatic. Otherwise, setting it to always-on will ensure
that the hard disk is always ready to receive data. If you intend to
operate an internal disk continuously, you should take care not to let it
overheat, since the interior of the DCM is well insulated.
disk.usagemode : This setting varies the way the DCM uses its hard
disk storage once it has been filled up.
•
The use-once option causes the DCM to stop recording data to
the hard disk, and discard any new data that arrives. It may still
send new data over the network, if you have so configured it,
but the hard disk will be untouched once full. Thus the
start
point of the stored data is known, but the end point depends on
the disk capacity. This is most useful for installations where you
are expecting to replace the hard disk periodically, or where you
need to take time-synchronized readings at several sites.
•
The recycle option causes the DCM to delete the oldest data files
on the hard disk to make space for incoming data. This way, the
end point of the stored data is known (it always includes the
most recent block of data), but the start point depends on the
disk capacity.
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