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Originally published in Queue vol. 9, no. 5
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(newest first)

Jered Floyd | Fri, 01 Jul 2011 02:14:46 UTC

The arguments you make are good to keep in mind when integrating deduplication at the block device rather than at the file system. With Albireo, we have experience with integration at both the block-level and the file system level; there are a number of trade-offs when considering at what point to add deduplication.

For this specific case, a sensible approach might be a protocol extension that allows a file system (or application) to indicate blocks that are not to be deduplicated. Much as TRIM allows SSDs to operate more efficiently and reliably, a UNIQUE extension would allow critical file system metadata to be preserved as multiple copies.

Jered Floyd CTO, Permabit Technology Corp.

Bill | Wed, 29 Jun 2011 13:07:36 UTC

I don't see this as an issue as reliability has moved to the controller level. Also the deduplication in an SSD is not the only thing going on, Sandforce controllers also have a RAID like architecture and very good EEC. I think the file systems you quoted are outdated, it may have been important 20 years ago but not now.

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