NAS-134418 / 25.04.0 / Deduplication fixes #279
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Since embedded blocks introduction 11 years ago, their writing was blocked if dedup is enabled. After searching through the modern code I see no reason for this restriction to exist. Same time embedded blocks are dramatically cheaper. Even regular write of so small blocks would likely be cheaper than deduplication, even if the last is successful, not mentioning otherwise. Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Signed-off-by: Alexander Motin <[email protected]> Sponsored by: iXsystems, Inc. Closes openzfs#17113
Implementation of DDT pruning introduced verification of DVAs in a block pointer during ddt_lookup() to not by mistake free previous pruned incarnation of the entry. But when writing a new block in zio_ddt_write() we might have the DVAs only from override pointer, which may never have "D" flag to be confused with pruned DDT entry, and we'll abandon those DVAs if we find a matching entry in DDT. This fixes deduplication for blocks written via dmu_sync() for purposes of indirect ZIL write records, that I have tested. And I suspect it might actually allow deduplication for Direct I/O, even though in an odd way -- first write block directly and then delete it later during TXG commit if found duplicate, which part I haven't tested. Reviewed-by: Tony Hutter <[email protected]> Signed-off-by: Alexander Motin <[email protected]> Sponsored by: iXsystems, Inc. Closes openzfs#17120
bugclerk
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ixhamza
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Mar 13, 2025
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Merge openzfs#17113 and openzfs#17120 .