Date: Sun, 27 Nov 2011 15:27:39 +0400 From: Lev Serebryakov <lev@FreeBSD.org> To: Kirk McKusick <mckusick@mckusick.com> Cc: freebsd-fs@FreeBSD.org Subject: Re: Does UFS2 send BIO_FLUSH to GEOM when update metadata (with softupdates)? Message-ID: <469709203.20111127152739@serebryakov.spb.ru> In-Reply-To: <201111261712.pAQHCY8G081783@chez.mckusick.com> References: <147455115.20111126115248@serebryakov.spb.ru> <201111261712.pAQHCY8G081783@chez.mckusick.com>
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Hello, Kirk. You wrote 26 =ED=EE=FF=E1=F0=FF 2011 =E3., 21:12:34: > Kostik has it right. The requirement for SU and SU+J is simply > that the underlying I/O subsystem not issue bio_done on a write > until it is on stable store. If the I/O subsystem wants to cache > it for a while (multiple seconds) before writing it to disk that > is fine (SU thinks in terms of 30-second intervals). The only Ok, These "multiple seconds" are good news. > thing that SU requires is that the subsystem NOT lie by issuing > the bio_done before it has committed the data to disk. Perhaps > what we need is a "delay acknowledgement until done' flag to make > this clear. Ok, such flag (and "30 seconds is Ok" statement) will be enough for me (RAID5) to implement robust but high-performance write queuing. But FSYNC flag will be nice and useful too, IMHO. --=20 // Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>
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