Re: fsync, rdiff-backup, wapbl, and WD Elements 1T drive

[christos%astron.com@localhost (Christos Zoulas)]

In article <201111010318.pA13IhOd001828%ginseng.pulsar-zone.net@localhost>,
Matthew Mondor  <mm_lists%pulsar-zone.net@localhost> wrote:
>On Mon, 31 Oct 2011 19:58:27 -0400
>Greg Troxel <gdt%ir.bbn.com@localhost> wrote:
>
>> Obligatory actual netbsd tech-kern content: It seems like we really need
>> a sync_synchronous(2) system call that guarantees that all file system
>> operations that have completed (syscall returned) before the issuance of
>> the sync_synchronous call are on disk before sync_synchronous returns.
>> It seems odd that for sync, there is no waiting, fsync seems to wait,
>> and fsync_range can flush or not flush caches, more or less.
>
>Hmm since in sync(2), the non-synchronous issue is noted as a bug:
>
>BUGS
>     sync() may return before the buffers are completely flushed.
>
>Does this mean that sync(2) should normally be synchronous and fixed to
>be, such that sync_synchronous(2) not be necessary?

Which sync man page are you reading? Ours has:

     Historically, sync() would schedule buffers for writing but not actually
     wait for the writes to finish.  It was necessary to issue a second or
     sometimes a third call to ensure that all buffers had in fact been writ-
     ten out.  In NetBSD, sync() does not return until all buffers have been
     written.

christos