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shag00
2020-04-21
2020-04-21
  • shag00

    shag00 - 2020-04-21

    I was syncing a disk and noticed a couple of things from the following 2 lines from the report generated to the terminal:
    1%, 899889 MB, 1239 MB/s, CPU 41%, 11:15 ETA
    61%, 29284912 MB, 656 MB/s, CPU 26%, 6:02 ETA

    First the MB is really Mb?
    Is it expected that the speed of the sync should deteriorate to such an extent, from 1239 MB/s to 656 MB/s and roughly half as much CPU? The decline is constant over many hours as these are just 2 of the many saves.

     
  • Walter Tuppa

    Walter Tuppa - 2020-04-21

    the disk rate depends mainly how many disk are used for parity generation. Just think a full and an almost empty disk. It starts with data from both disk and continues then with data only of the full disk (lower data rate). There is nothing wrong with this. The CPU usage also depends on this for parity calculation.

     
  • shag00

    shag00 - 2020-04-21

    I do not know how parity creation works but for the example above only 1 disk is being synced as it is a new disk to the array. Prior to the addition of this disk the array was fully synced.

     
  • Walter Tuppa

    Walter Tuppa - 2020-04-21

    a new disk means, that all others disk must be read, too, since parity is always over all disks. data read speed per second depends only on the number of disk have data and are used for parity calculation. I seems, that in your example, not all disks were filled equally.

     

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