On Thu, Sep 22, 2016 at 01:27:48AM +0200, Jarom??r Dole??ek wrote: > > 3.2 use FUA (Force Unit Access) for commit record write > This avoids need to issue even the second DIOCCACHESYNC, as flushing > the disk cache is not really all that useful, I like the thread over > at: > http://yarchive.net/comp/linux/drive_caches.html > Slightly less controversially, this would allow the rest of the > journal records to be written asynchronously, leaving them to execute > even after commit if so desired. It may be useful to have this > behaviour optional. I lean towards skipping the disk cache flush as > default behaviour however, if we implement write barrier for the > commit record (see below). > WAPBL would need to deal with drives without FUA, i.e fall back to cache > flush.
I have never understood this business about needing FUA to implement barriers. AFAICT, for any SCSI or SCSI-like disk device, all that is actually needed is to do standard writes with simple tags, and barrier writes with ordered tags. What am I missing? I must have proposed adding a B_ARRIER or B_ORDERED at least five times over the years. There are always objections... Thor
