On Tuesday 04 October 2005 11:31, Chris Lightfoot wrote: > The current ubd implementation doesn't support write > barriers (blk_queue_ordered etc.), and the reccomendation > is to use synchronous IO to ensure data integrity. In > principle, adding barrier request support ought to get > around this problem, allowing writes without O_SYNC with > occasional calls to fdatasync on the underlying data (the > motivation for write barrier support was safety of > journalling filesystems on disks with write caches, an > analogous problem). Yes, I more or less remembered that was the idea (from readings on lwn.net), thanks for confirming it. > ext3 and reiserfs support the write barrier stuff if > mounted with appropriate options (barrier=1 and > barrier=flush respectively). So they don't auto-enable this when support exists? I.e. everybody is running slower just because we don't add those params? > Implementing this ought to give performance somewhere > between ubdXs and ubdX, but with adequate guarantees of > data integrity for use with modern filesystems. That said, > I haven't measured this yet.
> A patch for this is pretty simple (see below). Has there > been discussion of this before? I couldn't find any in the > list archives.... This was discussed between me and Jeff recently, even if maybe that was off-list. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- This SF.Net email is sponsored by: Power Architecture Resource Center: Free content, downloads, discussions, and more. http://solutions.newsforge.com/ibmarch.tmpl _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
