Date: Fri, 17 Jun 2011 10:14:00 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Maxim Sobolev <sobomax@FreeBSD.org> Cc: svn-src-projects@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r223144 - projects/hastd_wan Message-ID: <20110617081400.GA1732@garage.freebsd.pl> In-Reply-To: <201106160844.p5G8iQ4W020318@svn.freebsd.org> References: <201106160844.p5G8iQ4W020318@svn.freebsd.org>
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--sdtB3X0nJg68CQEu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jun 16, 2011 at 08:44:26AM +0000, Maxim Sobolev wrote: > Author: sobomax > Date: Thu Jun 16 08:44:26 2011 > New Revision: 223144 > URL: http://svn.freebsd.org/changeset/base/223144 >=20 > Log: > "HAST currently doesn't support 'async' mode, so working over WAN is not > common use case for now, which makes your changes low priority. High > priority for HAST is working over LAN." -pjd > =20 > So this little fork of the hastd would aim at optimizing it for good > performance over WAN network. Hopefully it will be useful for somebody > else and and end up at least partially in the main tree. Let me share my ideas how I think 'async' should be implemented. In 'async' mode we send writes to the remote node, but don't wait for confirmation. This way we can complete the write much faster of course, but we still need to keep the extents dirty until remote node confirms that write succeeded. Then you need to limit the number of outstanding 'async' writes as we can easly consume huge amount of memory and make the activemap very dirty. Which shows that 'async' will only work for configuration where you have relatively short write peaks. Once that done you may think about combining outstanding I/Os and removing covered parts of earlier outstanding I/Os. --=20 Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://yomoli.com --sdtB3X0nJg68CQEu Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEYEARECAAYFAk37DMgACgkQForvXbEpPzTtCQCeLmV4uibXAtMGAjzFoU9uFKXb Gb0AniKcRSVH2xLPGXzWSOb28xvRsrs4 =MtV0 -----END PGP SIGNATURE----- --sdtB3X0nJg68CQEu--
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