2015-12-15 14:44 GMT+01:00 Phil Turmel <philip@xxxxxxxxxx>: > On 12/15/2015 06:30 AM, TheGerwazy . wrote: > >> The main problem is the data offsets are not stored elsewhere than in >> superblock. I have some drives from debian 6.0.5 and some were changed >> in debian 7.5. In 6.0.5 default data offset was at 2048 sector while >> int 7.5 it is 262144. > > There have been other defaults, and various adjustments to the > algorithms that handle special cases. The purpose of the superblock is > to store the data needed by the features supported. Where else > would/could you store this information? > maybe mdadm.conf, maybe syslog ? It the same problem like partitions, ext3 superblocks We need only a few parameters to recover whole array - some of them we could guess. Meybe its a good idea to spare some backups of mdadm superblock like in EXT3 ? Even though mdadm is, in my opinion, reliable system and I suggest it to my clients because of easy recovery. > This highlights why --create is such a terrible way to recover an array, > and highlights the danger posed by well-intentioned bloggers who > cavalierly suggest using it. > > Pretty much everyone who comes here for advice *before* trying --create > has been successfully helped. The results after --create are decidedly > mixed. Due to that there are production systems, sometimes there is no time to wait even an hour for advice - your boss would ask you "I need my data, why you are waitng ?" Another problem is when you are asking on the Internet - you sometimes receive completly wrong advice what lead you to losing the data... > >> Thanks for Phil > > You're welcome. > > Phil > Best regards, Gerard -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
