On Sunday August 23, for.poige+linux@xxxxxxxxx wrote: > 2009/8/23 NeilBrown <neilb@xxxxxxx>: > [...] > > Yes it will be updated. But if it is updated with a > > read-modify-write cycle then an old incorrect value will be updated > > to a new incorrect value, which doesn't help you much. > > I see. Thank you for the answer. My assumption was due thinking that > parity is never being used when RAID5 is in "healthy" mode. > > But anyway, please clear it up: if I've made --asume-clean RAID5 > array, formatted it with some FS (or even LVM), and put OS/data to it, > then (in idle at night, for e. g.) run "resync", would that be the > same valid result (overall data integrity) as if I had previously > created it without "--asume-clean" at all? (Let's suppose hard disks > were healthy in both cases :-) If by 'run "resync"' you mean echo repair > /sys/block/mdXX/md/sync_action then yes, what will have the same effect as not using --assume-clean to start with. > > And Neil, using the chance to have your reply :-) I'd like to ask one > more question: is that true (I think and hope it is!) that MD doesn't > read/write full chunk size when it's just to read/write another block > of data and hence chunk size only affects data interleaving on disks. That is correct - chunk size only affect data layout, not IO size. md/raid5 always reads or writes a whole page (normally 4K) at a time. NeilBrown > > P. S. Is there someone on this list who can share his linux-RAID > archive in mbox format? From time to time I find interesting > discussions have been going but can't just hit "Reply". If you can > help me with that, please reply personally (not CC:ing to the list). > Thanks! > > -- > End of message. Next message? -- 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
