>> In general an in-place migration is a very dangerous operation >> because it stresses existing hardware a lot plus it uses code >> that is rarely used and is quite complex. > But copying everything off will stress it just as much, > surely? The alternatives imho are worse ... * The very different access patterns of a block-by-block copy to new fresh disks and the migration-in-place having to rewrite by moving around the contents of all involved disks. * That in a copy there is always the original to fall back on, a migration-in-place that fails can be fatal. I am giving for granted here that one way or another at least one copy of all the data has to be done; and block-by-block device sequential copy is probably the best, followed by file-by-file sequential copy, followed by in-place migration. Note: RAID5 in-place migration does not mean that existing blocks stay where they are, it means that (nearly) all blocks get moved, but inside the existing device set. So probably the best combination here, because the O.P. does not currently have any redundancy, is to first ensure there is some kind of copy of the data and/or redundancy, on the way to getting a new storage layout. Because *any* whole-content data operation stresses the storage system. -- 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
