* [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
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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;
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^ 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
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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;
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^ permalink raw reply [flat|nested] 5+ messages in thread
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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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