From: Daira Hopwood Date: Thu, 5 Sep 2013 17:01:16 +0000 (+0100) Subject: Sun May 13 22:07:39 BST 2012 Brian Warner X-Git-Url: https://git.rkrishnan.org/reliability?a=commitdiff_plain;h=a8f07df233d1f0dc6cdce4da0abc8134d1521a96;p=tahoe-lafs%2Ftahoe-lafs.git Sun May 13 22:07:39 BST 2012 Brian Warner * performance.rst: small updates, mention (lack of) MDMF refs #1398 --- diff --git a/docs/performance.rst b/docs/performance.rst index 4657c151..1766d381 100644 --- a/docs/performance.rst +++ b/docs/performance.rst @@ -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.