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Question: Why does WAL not support directio? Is this intentionally designed that way? #12136

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zgcbj opened this issue Dec 12, 2023 · 1 comment
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Question: Why does WAL not support directio? Is this intentionally designed that way? #12136

zgcbj opened this issue Dec 12, 2023 · 1 comment

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@zgcbj
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zgcbj commented Dec 12, 2023

Why does WAL not support directio? Is this intentionally designed that way?
@ltamasi
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ltamasi commented Dec 12, 2023

Direct I/O is not a good match for the WAL (or the MANIFEST for that matter) because of the requirements it places on both the in-memory and on-disk addresses. Since you can only write entire (4K-aligned) 4K-sized pages this way, using direct I/O would entail rewriting previous records potentially several times (depending on record size), leading to increased write amp for the WAL (as well as potential corruptions).

@ltamasi ltamasi closed this as completed Dec 12, 2023
@cbi42 cbi42 mentioned this issue Feb 22, 2024
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@zgcbj @ltamasi