Les Mikesell <[email protected]> wrote on 09/17/2012 01:34:33 PM:
> On Mon, Sep 17, 2012 at 11:05 AM, Timothy J Massey
> <[email protected]> wrote:
> >
> >
> > I'm writing a longer reply, but here's a quick in-thread reply:
> >
> > I know exactly what you mean by waiting until after the first full.
Often
> > the second full will be faster -- but only *IF* you are bandwidth
limited
> > will you will see an improvement. In this case, neither him nor I are
> > bandwidth limited. I don't see an improvement.
>
> The 2nd might even be slower, since the server side has to decompress
> and recompute the checksums.
Interesting possibility. However, on the "big" server, it's new enough to
see the first backup. First one took 9987 minutes, and the second took
5558. The third took 5502. So there *was* a significant "speedup"
between the first and second. But I'm still only getting 442MB/minute, or
7MB/s. That server really should be able to get 5 times as much without
breaking a sweat. 1100 minutes is still a long time, but manageable. 5500
minutes is nearly four *days*... :(
> There's little risk of file-level corruption that would still let the
> checksums cached at the end of the file match unless you have bad RAM
> (which would likely cause crashes) or physical disk block corruption
> which you can check relatively quickly with a 'cat /dev/sd?
> >/dev/null' or a smartctl test run followed by checking the status.
It's disk block corruption caused by (silently) failing drives I'm most
worried about. It wasn't until a data-loss event a few months ago that I
found that smartd was not set up properly--and I'm not certain that SMART
would have actually helped in this case. (Fortunately, the loss of data
was on the backup server alone, and no one needed that data at that
moment, and my off-site archives were unaffected, but I still didn't like
it.) I *do* scrub the array (the default is weekly, I believe), and now
have both SMART and md configured to e-mail alerts.
But I still like the extra protection of *directly* comparing the files.
But not enough to take 4 days to do a backup! :)
I'm working on investigating each of these possibilities to improve
performance. I will let everyone know what I find.
Timothy J. Massey
Out of the Box Solutions, Inc.
Creative IT Solutions Made Simple!
http://www.OutOfTheBoxSolutions.com
[email protected]
22108 Harper Ave.
St. Clair Shores, MI 48080
Office: (800)750-4OBS (4627)
Cell: (586)945-8796
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