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performance.rst: small updates, mention (lack of) MDMF

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refs #1398
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Brian Warner 2012-05-13 14:07:39 -07:00
parent 6856e53b36
commit e850b54772
1 changed files with 11 additions and 1 deletions
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docs/performance.rst
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@ -28,6 +28,11 @@ written
``G`` indicates the number of storage servers on your grid
Most of these cost estimates may have a further constant multiplier: when a
formula says ``N/K*S``, the cost may actually be ``2*N/K*S`` or ``3*N/K*S``.
Also note that all references to mutable files are for SDMF-formatted files;
this document has not yet been updated to describe the MDMF format.
Publishing an ``A``-byte immutable file
=======================================
@ -210,10 +215,15 @@ cpu: variable, between ~A and ~N/K*A
network: variable; between A and N/K*A
memory footprint: (1+N/K)*S
memory footprint (immutable): (1+N/K)*S
(SDMF mutable): (1+N/K)*A
notes: To repair a file, Tahoe-LAFS downloads the file, and
generates/uploads missing shares in the same way as when it initially
uploads the file. So, depending on how many shares are missing, this
can cost as little as a download or as much as a download followed by
a full upload.
Since SDMF files have only one segment, which must be processed in its
entirety, repair requires a full-file download followed by a full-file
upload.