From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: <1d5d51400906281813g649a72f7v8610b0311c7de5f@mail.gmail.com> References: <1d5d51400906281813g649a72f7v8610b0311c7de5f@mail.gmail.com> Date: Mon, 29 Jun 2009 08:56:06 -0700 Message-ID: Subject: Re: [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac From: Russ Cox To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Topicbox-Message-UUID: 10fc6a46-ead5-11e9-9d60-3106f5b1d025 On Sun, Jun 28, 2009 at 6:13 PM, Fernan Bolando wr= ote: > man vac > "-q =C2=A0 =C2=A0Increase the performance of the -a or -d options by dete= cting > unchanged files based on a > =C2=A0 =C2=A0 =C2=A0 =C2=A0match of the files name and other meta data, r= ather than > examining the contents of the files" > > Why is -q not a default? Is there a reliability concern with that option? If the file contents change but the mtime and size remain the same, then vac -q will not notice the change and will not back up the new file contents. Some people worry about this case, others don't. Hence the flag. > I am currently doing an hourly backup using > > vac -d old_date-time.vac -f new_date-time.vac /home > which gives me a collection files with a date-time.vac filename. > > I am thinking I should just use vac -a main.vac /home > to switch to this method I only need to rename latest date-time.vac to ma= in.vac > and delete the other ones, right? vac -a creates a tree inside the vac archive. It expects the archive to have a top-level directory 2009 and subdirectories 0627, 0628, etc. You would need to change your vac tree to have that top-level structure before it would be valid input to vac -a. If you run it multiple times per day, the subdirectories for today would be named 0629, 0629.1, 0629.2, 0629.3, and so on. You can do this by building a local file tree with the right structure and using vac -m. On Sun, Jun 28, 2009 at 10:02 PM, Nathaniel W Filardo wrote= : > It uses an astronomically large amount of memory, if nothing else. > Mirroring a little over 100MB of data from sources with vac -q occupies > roughly 85MB in core. Whether you use -q should have no effect on the memory usage. There may be a memory leak somewhere involving -q, but at first glance I don't see one. Feel free to investigate. Russ