Disk reliability (Was: Node cloning)

Trent Piepho xyzzy at speakeasy.org
Fri Apr 6 16:14:33 EDT 2001

On Fri, 6 Apr 2001, Josip Loncaric wrote:
> BTW, the nonrecoverable error rate of 7200rpm IDE drives is typically
> rated at 1 part in 10^13, so you have a decent chance of finding
> problems in a 1-2 TB disk farm (which contains about 10^13 bits).

When a drive block goes bad, the drive automatically remaps it to a spare
block.  If you find bad blocks on a modern hard disk, something is wrong with
your drive.

> > BTW you can "mkswap -c" to mark bad blocks in swap. I don't know why
> > you'd find a bad block in swap less acceptable than a bad block in the
> > filesystem.
> As far as I know, "mkswap -c" only checks and reports the count of bad
> blocks, just in case you'd like to be told.  The man page does not say
> anything about *mapping* them out.  My understanding is that swap gets

Sure it does, from mkswap(8):

       The old setup wastes most of this bitmap page, because zero bits denote
       bad blocks or blocks past the end of the swap space, and a simple
       integer suffices to indicate the size of the swap space, while the bad
       blocks, if any, can simply be listed. 

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