From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: Hi! Is "container" more efficient in terms of I/O op. numbers ... Date: Fri, 25 May 2012 12:23:52 +1000 Message-ID: <20120525122352.07d186c2@notabene.brown> References: <20120525101424.3cb40eb2@notabene.brown> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/YonUOi2wXjXVDpLgzulN_AS"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: for.poige+linux@gmail.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/YonUOi2wXjXVDpLgzulN_AS Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 25 May 2012 09:52:52 +0800 Igor Podlesny wrote: > On 25 May 2012 08:14, NeilBrown wrote: > > On Thu, 24 May 2012 23:30:54 +0800 Igor Podlesny > > wrote: > > > >> =C2=A0 =C2=A0... then several "stand-alone" RAIDs on the same HDDs? --= Say, when > >> using write intent bitmaps. > >> > > > > I'm not sure you question exactly makes sense, but the answer would be = "no" > > if it did :-) >=20 > Well, due to disks seeks are expensive, hot data locality is > preferable and valuable thing, isn't it? > And it makes sense not only for WIB, but other frequent metadata > updates, doesn't it? >=20 Thank you for fleshing out your question a bit. It is always useful to sta= te your assumptions where asking a question as it makes it easier to understand and answer the question. The general metadata isn't updated very often - not often enough to justify any particular concern for where it is placed. For a 'reshape' it can be updated more often, but that is an unusual situation. bitmap metadata certainly can be updated often, but there is no container format currently supported which makes use of write-intent bitmaps, so thinking about containers for bitmaps is not relevant. If it were, it would make sense to keep the bitmap close to the data that it described, so having a container arrangement would not be better than individual arrays. It maybe be worse depending on the particular details. Does that make sense? NeilBrown --Sig_/YonUOi2wXjXVDpLgzulN_AS Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT77tODnsnt1WYoG5AQIi6xAAj4+4tuhKs2BoLeFgoBFHHWojJIPS4eaT hVnNi8gP7jJ1ho3RmdOPH7HZmgG6/be36mwIqeJLIkKcnWwi4Go/vYJb/SqcyPlK rl6aNpxdLMdV66wRYr7LWH4QnbVmirEdsTzFU702IhXN9w7lFNtKpT6gyU5eZg80 QDia2feooiCBgNZq0BhvJtVcQ7/1PO/bUZF80QMnZXy1raz7xgQxcUGNsXWRo/2A RZIQEijBGNrUxsLNdrtwekPFggPFRkA3Jhf7prHqWVNj1KR/+n7DU+YtlmAUqCqv G3FyS6gi6ktmmMs/T63sjFFe24eV+kp43IxIGw636AkFIXko1CU9AR0vMKDaGRl5 lEbgNpLfwJ9BNXDNQs9we+t77w/e40mL72Lwib70BHN2icl+BxuirG2//lLFFbE/ dIRT5M10tAevxpPQDkyZgAQf/xRg3MvLbflMeC3PUrkPezyRpYFIMSjcIWJcU7sa cr3IeaUtd6VVzOmGIg6sOf5qMPu01XHpW8wuqcHolEuYiawEUzX4Ul89dCCfgAui npt9SoXUwZHAY+DRqNY2Bo1b+rdkJ/KWmZmzUlqSC0jiFvaMltCUdcR4ESRq3bQ9 Z3LUH17iOlc99V0XGugzQhgPMvuEabdY9adIwCdGiMZlgF/rs9A1yszCSURbryhW +sPevS7YtWU= =6rC+ -----END PGP SIGNATURE----- --Sig_/YonUOi2wXjXVDpLgzulN_AS--