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From Raghu Angadi <rang...@apache.org>
Subject Re: DataBlockScanner scan period
Date Fri, 15 Oct 2010 17:48:09 GMT
On Wed, Oct 13, 2010 at 5:01 PM, Thanh Do <thanhdo@cs.wisc.edu> wrote:

> Hi again,
>
> Could any body explain to me about the scanning period
> policy of DataBlockScanner? That is who often it wake up
> and scan a block file.
> When looking at the code, I found
>
>  static final long DEFAULT_SCAN_PERIOD_HOURS = 21*24L; // three weeks
>
but definitely it does not wake up and pick a random block
> to verify every three weeks, right?
>

of course, not.

The scanner is always alive. It paces itself so that it scans all the blocks
in 3 weeks. So if a datanode has just 210 blocks, it would be scanning about
10 a day.

Raghu.


> Thanks a lot,
> Thanh
>
>

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