From: Brian Warner Date: Mon, 11 Jan 2010 19:01:32 +0000 (-0800) Subject: NEWS: improve "tahoe backup" notes, mention first-backup-after-upgrade duration X-Git-Url: https://git.rkrishnan.org/%5B/frontends/%3C?a=commitdiff_plain;h=222148eaeeaca5671fa949e4a2e62549cb83d4f9;p=tahoe-lafs%2Ftahoe-lafs.git NEWS: improve "tahoe backup" notes, mention first-backup-after-upgrade duration Thanks to Francois Deppierraz for the suggestion. --- diff --git a/NEWS b/NEWS index 9c1d69e6..9119f956 100644 --- a/NEWS +++ b/NEWS @@ -33,18 +33,31 @@ directories. See docs/frontends/webapi.txt for details. The "tahoe backup" command has been enhanced to create immutable directories (in previous releases, it created read-only mutable directories). This is significantly faster, since it does not need to create an RSA keypair for -each new directory. In addition, "DIR-IMM" immutable directories are -repairable, unlike "DIR-RO" read-only mutable directories (at least in this -release; a future Tahoe release should be able to repair DIR-RO). +each new directory. Also "DIR-IMM" immutable directories are repairable, +unlike "DIR-RO" read-only mutable directories (at least in this release: a +future Tahoe release should be able to repair DIR-RO). In addition, the backupdb (used by "tahoe backup" to remember what it has already copied) has been enhanced to store information about existing immutable directories. This allows it to re-use directories that have moved but still contain identical contents, or which have been deleted and later replaced. (the 1.5.0 "tahoe backup" command could only re-use directories -that were in the same place as they were in the previous backup). With this -change, the backup process no longer needs to read the previous snapshot out -of the Tahoe grid, reducing the network load considerably. +that were in the same place as they were in the immediately previous backup). +With this change, the backup process no longer needs to read the previous +snapshot out of the Tahoe grid, reducing the network load considerably. + +A "null backup" (in which nothing has changed since the previous backup) will +require only two Tahoe-side operations: one to add an Archives/$TIMESTAMP +entry, and a second to update the Latest/ link. On the local disk side, it +will readdir() all your local directories and stat() all your local files. + +If you've been using "tahoe backup" for a while, you will notice that your +first use of it after upgrading to 1.6.0 may take a long time: it must create +proper immutable versions of all the old read-only mutable directories. This +process won't take as long as the initial backup (where all the file contents +had to be uploaded too): it will require time proportional to the number and +size of your directories. After this initial pass, all subsequent passes +should take a tiny fraction of the time. As noted above, Tahoe versions earlier than 1.5.0 cannot read immutable directories.