Minicom Advanced Systems CMG-DCM manual Cmg-Dcm

CMG-DCM

Once the operating system is loaded, the main Flash memory blocks (where present) are mounted on /nand0 and /nand1. Incoming data, which may be from several sources, is combined into a single stream and placed in one of

these blocks (whichever is less full). When in use, you can expect each to be between 50% and 75% full, with several da:ta files present. If the DCM is using GCF as its storage file format (recommended; see Section 4.2, “Disk”), then each file will be named after the timestamp on its first packet of data, in the following fashion:

file-yyyymmdd-jjj-s-cccccccc.gcf where yyyymmdd represents the date of the earliest data packet in the file, jjj the number of full days elapsed since midnight on January 1, s the time segment within the day (each day is divided into eight 3-hour segments), and cccccccc a unique hexadecimal code included to ensure filenames do not coincide.

When one of the Flash memory blocks approaches capacity, or after a fixed time period (if you have so configured it; see Section 4.2, “Disk”) the DCM will automatically move them onto the primary USB hard disk. This may be either an internal Lacie hard disk, or an external drive connected to the module through a USB client interface. This disk uses a specially-designed journalled filesystem, which is designed to maintain the integrity of your data at all times. Even if a write operation fails or is aborted suddenly, the disk will still contain a valid filesystem with all previously-saved data intact, which can be read using any driver that supports FAT32.

There is a set of specialised commands which allow you to perform basic tasks on this filesystem:

gfat32df : Displays the size of the filesystem, and how much free space remains, in a format similar to this:

FAT32 filesystem has 15 G bytes free

Partition is 37 G bytes (78140097 blocks of 512 bytes)

If no suitable storage medium can be found, you will see the message Failed to find a USB disk.

diskman : Ensures that the /nandx partitions do not become full by moving files when necessary. This program ordinarily runs constantly in the background. However, a user can use the command diskman -fto force the Flash memory to be entirely copied to the USB disk. Typing diskman -fis identical to clicking the Flush flash button on the Disk tools page (see “Flush

flash” in Section 5.3). It does not remove data from the Flash memory. If you issue diskman -fand then swap hard disks, the data remaining in memory will later be written out to the new hard disk, causing some overlap between it

and the old disk.

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