Mark 5 module recovery

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    Comparing version 17:51, 23 Jan 2019 by jwagner with version 18:11, 23 Jan 2019 by jwagner.

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    A recovery script now found in the DiFX repository (https://svn.atnf.csiro.au/difx/sites/MPIfR/mark5/mark5_scan_recovery.py)

    Reverse Engineered Mark5 Disk Structure

    A certain H.V. at JIVE has reverse engineered the Mark5 data block structure. Mark5 recordings are scattered as 2^16 -byte sized blocks, written round-robin to disks of a module. Each block has a 8-byte header. The first 4 bytes are unused. The next 4 bytes (32 bit unsigned int) contain a sequence number in the upper 28 bits. The rest of the block contains VLBI data.

    The sequences numbers of the blocks allow 1) detection of the original ordering of disks in a module, 2) detection of lost disks (lost blocks).

    A certain J.W. at MPIfR spotted the User Directory storage area on the raw disks. The user directory is located at 11272704 bytes before the end of every disk. Each disk should contain an identical copy of the user directory.

    Contents of a disk set can be recovered with https://svn.atnf.csiro.au/difx/sites/MPIfR/mark5/mark5_scan_recovery.py

    Version from 17:51, 23 Jan 2019

    This revision modified by jwagner (Ban)

    ...

    Version as of 18:11, 23 Jan 2019

    This revision modified by jwagner (Ban)

    ...

    A recovery script now found in the DiFX repository (https://svn.atnf.csiro.au/difx/sites/MPIfR/mark5/mark5_scan_recovery.py)

    Reverse Engineered Mark5 Disk Structure

    A certain H.V. at JIVE has reverse engineered the Mark5 data block structure. Mark5 recordings are scattered as 2^16 -byte sized blocks, written round-robin to disks of a module. Each block has a 8-byte header. The first 4 bytes are unused. The next 4 bytes (32 bit unsigned int) contain a sequence number in the upper 28 bits. The rest of the block contains VLBI data.

    The sequences numbers of the blocks allow 1) detection of the original ordering of disks in a module, 2) detection of lost disks (lost blocks).

    A certain J.W. at MPIfR spotted the User Directory storage area on the raw disks. The user directory is located at 11272704 bytes before the end of every disk. Each disk should contain an identical copy of the user directory.

    Contents of a disk set can be recovered with https://svn.atnf.csiro.au/difx/sites/MPIfR/mark5/mark5_scan_recovery.py