On Saturday 09 of July 2011 08:19:30 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. Only a problem in a single disk installation > 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. There is a difference between root inode copies, don't think there's any difference between metadata tree copies. I'm quite certain they are bit for bit identical. > 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. That would be a big change for little to no benefit. > 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? You shouldn't depend on single drive, metadata raid is there to protect against single bad blocks, not disk crash. If you want redundancy, use mulitple disks. Either HDD or SSD. And have readable backups. Regards, Hubert
Attachment:
signature.asc
Description: This is a digitally signed message part.
