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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1717) Cassandra cannot detect corrupt-but-readable column data
Date Fri, 05 Aug 2011 13:03:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13079951#comment-13079951
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Sylvain Lebresne commented on CASSANDRA-1717:
---------------------------------------------

bq. So can't you just implement a no-op compression option

That is exactly what I had in mind for "maybe in an uncompressed mode for which mmap would
be deactivated". It will be trivial once we have made it easy to switch compression algorithm
(which is trivial too btw, I'll do that probably ... well why not now).

That would make things fairly clear imho. We would say "no mmap" with compression and no checksum
without compression, but you have the "compression with no-op algorithm". This has my preference
as said previously, but we must be aware that people will ask why we have a non-mmap non compressed
mode and a compressed no-op mode (we cannot really get rid of the first one because otherwise
we say "you shall use mmap forever now").

> Cassandra cannot detect corrupt-but-readable column data
> --------------------------------------------------------
>
>                 Key: CASSANDRA-1717
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1717
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Pavel Yaskevich
>             Fix For: 1.0
>
>         Attachments: checksums.txt
>
>
> Most corruptions of on-disk data due to bitrot render the column (or row) unreadable,
so the data can be replaced by read repair or anti-entropy.  But if the corruption keeps column
data readable we do not detect it, and if it corrupts to a higher timestamp value can even
resist being overwritten by newer values.

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