disParity » General Discussion

Should deletes reduce the parity footprint?

(2 posts)
  1. airjrdn
    Member

    I've been testing disParity lately and noticed that when I deleted ~25G of data from my largest dataX, the total size of the parity store didn't decrease. Should it have?

    For example, I have the following config:

    parity=G:\

    data1=H:\
    data2=I:\
    data3=J:\
    data4=K:\
    data5=L:\
    data6=P:\
    data7=U:\
    data8=D:\Images\

    G, H, and I are 1TB drives, the rest are smaller. H had the most data, with only a couple of GBs free. G probably had 30G or so free.

    I ran a create, and a day and a half or so later, it was done (G is an external USB drive, so that was probably the bottleneck). The amount of free space on G was pretty close to the same as H.

    After that, I deleted 25G or so from H and ran an update. I assumed the free space on G would increase, but it didn't. Should it have?

    Posted 4 years ago #
  2. Roland
    Roland

    No, deletes will not change the size of previously generated parity, but they do leave "holes" in the parity files that will be filled by later adds on that same drive, if they can fit.

    To reduce the total parity size after a delete, disParity would have to perform the equivalent of defragmentation pass on the entire parity set, which would be prohibitively expensive.

    If you *really* want the parity size to reduce after deleting a lot of files, you can always run the "create" command again and build a new parity set.

    Posted 4 years ago #

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