[tahoe-lafs-trac-stream] [tahoe-lafs] #1885: cloud backend: redundant reads of chunks from cloud when downloading large MDMF file (was: cloud backend: redundant reads of chunks from S3 when downloading large MDMF file)

[tahoe-lafs]

#1885: cloud backend: redundant reads of chunks from cloud when downloading large
MDMF file
-------------------------+-------------------------------------------------
     Reporter:           |      Owner:
  davidsarah             |     Status:  new
         Type:  defect   |  Milestone:  1.11.0
     Priority:  normal   |    Version:  1.9.2
    Component:  code-    |   Keywords:  cloud-backend cache download
  storage                |  performance mdmf
   Resolution:           |
Launchpad Bug:           |
-------------------------+-------------------------------------------------
Description changed by daira:

Old description:

> I uploaded a 7.7 MiB video as an MDMF file using the cloud backend (as of
> [https://github.com/davidsarah/tahoe-
> lafs/commit/022796fb7813c2f42d668a0ee3de9abae869deb5 1819-cloud-
> merge/022796fb]), and then downloaded it. From {{{flogtool tail}}}ing the
> storage server, I saw that it was reading the same chunks multiple times
> during the download. That suggests that the chunk cache is not operating
> well enough.
>
> The file was being downloaded by playing it as a video in Chromium; I
> don't think that makes a difference.

New description:

 I uploaded a 7.7 MiB video as an MDMF file using the cloud backend (as of
 [https://github.com/davidsarah/tahoe-
 lafs/commit/022796fb7813c2f42d668a0ee3de9abae869deb5 1819-cloud-
 merge/022796fb]), and then downloaded it. From {{{flogtool tail}}}ing the
 storage server, I saw that it was reading the same chunks multiple times
 during the download. That suggests that the chunk cache is not operating
 well enough.

 The file was being downloaded by playing it as a video in Chromium; I
 don't think that makes a difference.

--

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1885#comment:3>
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