* [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac @ 2009-06-29 1:13 Fernan Bolando 2009-06-29 5:02 ` Nathaniel W Filardo 2009-06-29 15:56 ` [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Russ Cox 0 siblings, 2 replies; 5+ messages in thread From: Fernan Bolando @ 2009-06-29 1:13 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs Hi The p9p vac discussion made me re-think the way I use vac. man vac "-q Increase the performance of the -a or -d options by detecting unchanged files based on a match of the files name and other meta data, rather than examining the contents of the files" Why is -q not a default? Is there a reliability concern with that option? 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 main.vac and delete the other ones, right? fernan -- http://www.fernski.com ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac 2009-06-29 1:13 [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Fernan Bolando @ 2009-06-29 5:02 ` Nathaniel W Filardo 2009-06-29 12:23 ` [9fans] when to use vac -q -d old.vac instead of simply vac -dold.vac erik quanstrom 2009-06-29 15:56 ` [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Russ Cox 1 sibling, 1 reply; 5+ messages in thread From: Nathaniel W Filardo @ 2009-06-29 5:02 UTC (permalink / raw) To: fernanbolando, Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 318 bytes --] On Mon, Jun 29, 2009 at 09:13:09AM +0800, Fernan Bolando wrote: > Why is -q not a default? Is there a reliability concern with that option? 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. --nwf; [-- Attachment #2: Type: application/pgp-signature, Size: 204 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [9fans] when to use vac -q -d old.vac instead of simply vac -dold.vac 2009-06-29 5:02 ` Nathaniel W Filardo @ 2009-06-29 12:23 ` erik quanstrom 0 siblings, 0 replies; 5+ messages in thread From: erik quanstrom @ 2009-06-29 12:23 UTC (permalink / raw) To: 9fans > On Mon, Jun 29, 2009 at 09:13:09AM +0800, Fernan Bolando wrote: > > Why is -q not a default? Is there a reliability concern with that option? > > 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. one would think that 20 bytes per file + fixed buffer would be enough. - erik ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac 2009-06-29 1:13 [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Fernan Bolando 2009-06-29 5:02 ` Nathaniel W Filardo @ 2009-06-29 15:56 ` Russ Cox 2009-07-02 1:54 ` Nathaniel W Filardo 1 sibling, 1 reply; 5+ messages in thread From: Russ Cox @ 2009-06-29 15:56 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs On Sun, Jun 28, 2009 at 6:13 PM, Fernan Bolando<fernanbolando@mailc.net> wrote: > man vac > "-q Increase the performance of the -a or -d options by detecting > unchanged files based on a > match of the files name and other meta data, rather 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 main.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<nwf@cs.jhu.edu> 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac 2009-06-29 15:56 ` [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Russ Cox @ 2009-07-02 1:54 ` Nathaniel W Filardo 0 siblings, 0 replies; 5+ messages in thread From: Nathaniel W Filardo @ 2009-07-02 1:54 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 362 bytes --] On Mon, Jun 29, 2009 at 08:56:06AM -0700, Russ Cox wrote: > 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. You're right; I glitched. The memory consumption is due to -d, not -q, of course. Sorry for the noise. --nwf; [-- Attachment #2: Type: application/pgp-signature, Size: 204 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2009-07-02 1:54 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2009-06-29 1:13 [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Fernan Bolando 2009-06-29 5:02 ` Nathaniel W Filardo 2009-06-29 12:23 ` [9fans] when to use vac -q -d old.vac instead of simply vac -dold.vac erik quanstrom 2009-06-29 15:56 ` [9fans] when to use vac -q -d old.vac instead of simply vac -d old.vac Russ Cox 2009-07-02 1:54 ` Nathaniel W Filardo
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