Date: Tue, 7 Jun 2005 21:40:05 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Ivan Voras <ivoras@fer.hr> Cc: hackers@freebsd.org, scottl@FreeBSD.org, phk@FreeBSD.org Subject: Re: Google SoC idea Message-ID: <20050607194005.GG837@darkness.comp.waw.pl> In-Reply-To: <42A475AB.6020808@fer.hr> References: <42A475AB.6020808@fer.hr>
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--AG6PiNxwwkUqaz46 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 06, 2005 at 06:11:23PM +0200, Ivan Voras wrote: +> I have an idea that I could implement through Google's "Summer of Code"= =20 +> project, but as I have little experience with stuff it involves (kernel= =20 +> programming / disks / filesystem optimization), so I expect any answer= =20 +> from "It won't work" or "It's useless" to "It can't be done". :) +>=20 +> The idea is this: to implement sort of GEOM-layer disk data journaling= =20 +> system. I imagine it to be a GEOM class using two "lower-level" devices:= =20 +> one for data and one for the "journal" (this way, the journal device can= =20 +> be on a fast and small disk). Such journaled device could be used to=20 +> host any filesystem, probably mounted with synchronoues-access, and it= =20 +> will result in faster write access by keeping the writes sequential in= =20 +> the "journal" device. Journal information will be commited to the data= =20 +> disk periodically by a separate log-writer thread, or when it gets full.= =20 +> The "data disk" will be consistent so it can be used without it's=20 +> "journal" part (after a clean disconnect/rebuild) if needed. At the=20 +> worst case, I think this will help performance in cases when there's a= =20 +> burst of write activity followed by a period of IO idleness. +>=20 +> I've made the above idea more-or-less from my head in one afternoon, so= =20 +> it's perfectly possible that I'm missing some vital point or that it's= =20 +> complete nonsense :) +>=20 +> Does it make sense to do it this way? Is it worth applying for the SoC? Not sure. Basically this is simlar what softupdate does, I think. =46rom another point of view softupdates are only available for UFS. You probably wants to hear scottl and phk opinions (CCed). --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --AG6PiNxwwkUqaz46 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFCpfgVForvXbEpPzQRAulyAKDRdFAB5RebkoghErbCJRqidowyCgCg6j/V Inrlfvv6F5+Hwq+VvjImM4Y= =wc9J -----END PGP SIGNATURE----- --AG6PiNxwwkUqaz46--
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