Greetings, On Wed, Nov 16, 2011 at 7:55 PM, Steven Whitehouse <swhiteho@xxxxxxxxxx> wrote: > Hi, > > On Wed, 2011-11-16 at 19:44 +0530, Rajagopal Swaminathan wrote: >> Greetings, >> >> On Wed, Nov 16, 2011 at 7:13 PM, Bob Peterson <rpeterso@xxxxxxxxxx> wrote: > I'm not quite sure which feature you are suggesting that we take, but > I'd be surprised that if the start of a ZFS filesystem were to be > overwritten that it could be easily reconstructed. Well, Self correction/healing like some kinda block level CRC check? Cores are cheap nowadays. I do understand that I/O is still expensive at the OS level. I would anyday prefer a MD raid to h/w raid as the disk can be simply ported to another system and the RAID lives. I know I am being a bit (or a lot) vague here. > > The problem here is "how much is enough?". If we kept the first 8 blocks > of the fs duplicated, then someone would come along and overwrite the > first 16 and them say why did you choose only 8? We could duplicate > everything, but then why not simply mirror at the block device level? > Now, I _did_ opine on the matter of the sysadmin managing a cluster who does not monitor any command/process which does low level access to disk. I can't comment on some RDBMS preferring "Raw devices". > Which is not to say that we couldn't usefully learn a few lessons from > what other filesystems are doing, but only that I'm not sure that it > would help for this particular issue. > IMHO, It is quite simple: have multiple backups of critical data at every level -- be it block level, filesystem, files etc. etc., if not pragmatic in local, then a remote system. I have implemented at least a few RHCS way back in 2007-2009. Some, who could afford, were using storage (like IBM DS<something>, Sun<somemodel>, HP<somemodel>) and, many, DRBD. Apologies if I sounded arrogant, It is just the pain I have encountered when it comes to cost. Well, again, above just my IMHO. -- Regards, Rajagopal -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster