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https://issues.apache.org/jira/browse/CASSANDRA-182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709929#action_12709929
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Sandeep Tata commented on CASSANDRA-182:
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FastSync (inappropriately named, IMHO) option tells the CommitLog to use a
FastConcurrentWriter. This certainly doesn't force to disk, and therefore is
not an option for durable writes.
If we don't add a third option for 0.3 which forces to disk, we simply have
*no* durable writes. Even on blocking writes, it is possible that the data has
not hit disk in any of the replica's logs.
We have two options:
1. Release as is, and say "we don't offer durable writes yet"
2. Add an option to force the logs and say "this is currently a low-performing
option and will be improved for 0.4"
We can do the forces in CommitLog (probably a cleaner approach in terms of
eliminating unnecessary forces, but updateHeader writes only for CFs
encountered for the first time). The approach in CASSANDRA-182.patch seemed
minimally invasive to me :-)
Building a well-tested high-performance logger will take significantly more
time. (Just testing the logger for correctness is non-trivial.)
> CommitLog.add doesn't really force to disk
> ------------------------------------------
>
> Key: CASSANDRA-182
> URL: https://issues.apache.org/jira/browse/CASSANDRA-182
> Project: Cassandra
> Issue Type: Bug
> Affects Versions: trunk, 0.3
> Reporter: Sandeep Tata
> Assignee: Sandeep Tata
> Fix For: trunk, 0.3
>
> Attachments: CASSANDRA-182.patch
>
>
> CommitLog.add does't really force writes to disk. This could result in acked
> writes being lost.
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