On Tue, Mar 25, 2008 at 12:47:50PM -0400, Theodore Tso wrote: > > Well 2TB, assuming a 4k blocksize, means a block bitmap is 512 megs. > So at least for ext3, 4GB should be just enough, unless you hit > certainly really nasty complicated corruptions (i.e. large number of > blocks claimed by more than one inode, which can happen if an inode > table is written to the wrong location on disk --- on top of some > other portion of the inode table), or if the filesystem has a large > number of files with hard links (such as the case with certain backup > programs). Whoops, screwed up my math. The block bitmap for a 2TB filesystem is 64 megs, not 512 megs. 2*41 / 2**12 / 2**3 == 2**26, or 64mb. E2fsck in the worst case will allocate 5 inode bitmaps and 3 block bitmaps, plus various arrays for directory blocks and keeping track of refcounts (which are optimized for counnts of 0 and 1, so lots of hard links will blow up your memory usage, although we do have a tdb option which helps in that particular case). So I'd say that most of the time 3GB of address space should really be enough for a 2TB raid array, unless you get really pathalogical corruption cases. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
