On Sun, Jan 24, 2010 at 7:48 PM, Marco Peereboom <sl...@peereboom.us> wrote: > On Sun, Jan 24, 2010 at 07:22:08PM -0500, nixlists wrote: >> On Sun, Jan 24, 2010 at 12:22 PM, Jonathan Thornburg >> <jth...@astro.indiana.edu> wrote: >> > In message <http://marc.info/?l=openbsd-misc&m=126356588306613&w=1>, >> > Marco Peereboom <slash () peereboom ! us> wrote >> >> You can do everything right all day long in software but hardware does >> >> what it does and claiming that a piece of software is crash proof is >> >> naive at best. >> > >> > Hmm. Our rename(2) man page currently says: >> > >> > rename() guarantees that if _to_ already exists, an instance of _to_ >> > will always exist, even if the system should crash in the middle of >> > the operation. >> > >> > Should this perhaps be changed to read something like this? >> > >> > rename() tries to guarantee that if _to_ already exists, an instance >> > of _to_ will always exist, even if the system should crash in the >> > middle of the operation. However, in some cases the hardware may >> > not provide the proper support, causing the guarantee to fail. >> > >> > Or do we (as a general policy) take this sort of escape clause taken to >> > be implied to knowledgable readers, and thus need not be explicitly stated? >> >> It's of course implied that hardware and FFS work as they should for >> the guarantee to work, but... > > Virtually all PATA & SATA disks have write back cache enabled. Some FC, > SCSI and SAS do too. > >> No one seems to want or be able to point out any particular hardware >> that rename() (and subsequently FFS and MTAs) fail on! > > Virtually all PATA & SATA disks have write back cache enabled. Some FC, > SCSI and SAS do too.
>> When configured as documented - no controller write-back cache (maybe >> with a battery back-up, but batteries fail too), no drive write-back >> cache, no async mounts, no known buggy stuff. I specifically wrote above "When configured as documented." No admin will run a mail server with write-back cache enabled on either controller or drives (well, maybe with a battery back-up, but I'll say again that batteries fail too). You seem to be taking what I wrote out of context, or you are assuming that I am a moron who doesn't know the basics and run mail servers with write-back cache on controllers and drives. > Hope you now know that virtually all PATA & SATA have WB cache enabled. Of course I know, as was stated in the previous message, but of course, as most people, I disable it. Don't twist what I said. If you read the previous email again, you'll see that I say "no write-back cache.". Please, point me to hardware that, when met all the above conditions, is still unreliable for rename(). It would benefit thousands of people running mail servers. Thanks!
