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https://issues.apache.org/jira/browse/IGNITE-29175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18140207#comment-18140207
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Ignite TC Bot commented on IGNITE-29175:
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"Snapshots: Fixed restoration of compressed cache partitions to preserve sparse
disk allocation."
The Release Note field has been filled with the wording above. Please review it
and edit it if needed.
> Copy compressed snapshot partitions sparsely on restore instead of punching
> holes
> ---------------------------------------------------------------------------------
>
> Key: IGNITE-29175
> URL: https://issues.apache.org/jira/browse/IGNITE-29175
> Project: Ignite
> Issue Type: Improvement
> Reporter: Nikita Amelchev
> Assignee: Nikita Amelchev
> Priority: Major
> Fix For: 2.19
>
> Time Spent: 2h 10m
> Remaining Estimate: 0h
>
> Partition files of a compressed cache group are sparse: each page keeps only
> its compressed bytes,
> the rest of the page is a hole.
>
> When such a group is restored from a snapshot, every partition goes through
> two passes:
> - the file is copied as a dense file, so the holes turn into zeros on disk;
> - the copy is read again page by page, and a hole is punched after each page
> with a separate fallocate call.
> On a store with many partitions this makes the restore much slower than
> creating the same snapshot.
>
> The copy can write only the compressed bytes of each page instead: the file
> system leaves the rest
> of the page unallocated, and the second pass is not needed.
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