[lkml]   [2001]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Journaling pointless with today's hard disks?
Andrew Morton wrote:

> "H. Peter Anvin" wrote:
>>Followup to: <9tumf0$dvr$>
>>By author: "H. Peter Anvin" <>
>>In newsgroup:
>>>Indeed; having explicit write barriers would be a very useful feature,
>>>but the drives MUST default to strict ordering unless reordering (with
>>>write barriers) have been enabled explicitly by the OS.
>>On the subject of write barriers... such a setup probably should have
>>a serial number field for each write barrier command, and a "WAIT FOR
>>WRITE BARRIER NUMBER #" command -- which will wait until all writes
>>preceeding the specified write barrier has been committed to stable
>>storage. It might also be worthwhile to have the equivalent
>>nonblocking operation -- QUERY LAST WRITE BARRIER COMMITTED.
> For ext3 at least, all that is needed is a barrier which says
> "don't reorder writes across here". Asynchronous behaviour
> beyond that is OK - the disk is free to queue multiple transactions
> internally as long as the barriers are observed. If the power
> goes out we'll just recover up to and including the last-written
> commit block.

Waiting for write barriers to clear is key to implementing fsync()
efficiently and correctly.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:13    [W:0.533 / U:0.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site