On Friday 07 August 2015 11:40:24 Mike Fleetwood wrote: > On 7 August 2015 at 10:47, Sjoerd <sjoerd@xxxxxxxxx> wrote: > > While we're at it: any idea why the default for SSD's is single for meta > > data as described on the wiki? > > (https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices > > #Filesystem_creation) > > > > I was looking for an answer why my SSD just had single metadata, while I > > expected it to be DUP and stumbled on this wiki article. Can't find a > > reason for why a SSD would be different? > > > > Cheers, > > Sjoerd > > I would assume that it is because some SSD drives controllers > deduplicate by default [1]. The developers probably think that when > it comes to your data the truth, no mater how ugly, is preferable to a > false sense of security. (Btrfs thinking it has 2 copies of metadata > when the SSD drive only actually has stored 1 copy). > > [1] How SSDs can hose your data > http://www.zdnet.com/article/how-ssds-can-hose-your-data/ > "Researchers found that at least 1 Sandforce SSD controller - the > SF1200 - does block-level deduplication by default. Which can be a > problem. > > Many file systems - NTFS, most Unix/Linux FSs, ZFS are some - write > critical metadata to multiple blocks in case one copy gets corrupted. > But what if, unbeknownst to you, your SSD de-duplicates that block, > leaving your file system with only 1 copy? " > > Thanks, > Mike Thanks for the explanation Mike...sounds plausible.. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
