On Sat, 2011-07-09 at 08:19 +0200, Paweł Brodacki wrote: > Hello, > > I've stumbled upon this article: > http://storagemojo.com/2011/06/27/de-dup-too-much-of-good-thing/ > > Reportedly Sandforce SF1200 SSD controller does internally block-level > data de-duplication. This effectively removes the additional > protection given by writing multiple metadata copies. This technique > may be used, or can be used in the future by manufactureres of other > drives too. > > I would like to ask, if the metadata copies written to a btrfs system > with enabled metadata mirroring are identical, or is there something > that makes them unique on-disk, therefore preventing their > de-duplication. I tried googling for the answer, but didn't net > anything that would answer my question. > > If the metadata copies are identical, I'd like to ask if it would be > possible to change this without major disruption? I know that changes > to on-disk format aren't a thing made lightly, but I'd be grateful for > any comments. > > The increase of the risk of file system corruption introduced by data > de-duplication on Sandforce controllers was down-played in the > vendor's reply included in the article, but still, what's the point of > duplicating metadata on file system level, if storage below can remove > that redundancy? > > Regards, > Paweł
Hello, Sorry I add my 0.03$. It is possible to workaround it by using encryption. If something other then ebc is used the identical elements in unecrypted mode are stored as different on hdd. The drawbacks: - Encryption overhead (you may want to use non-secure mode as you're not interested in security) - There is avalanche effect (whole [encryption] block gets corrupted even if one bit of block is corrupted). Regards
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