From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Queuing of dm-raid1 resyncs to the same underlying block devices Date: Fri, 09 Oct 2015 09:01:29 +1100 Message-ID: <87d1wp58au.fsf@notabene.neil.brown.name> References: <20150926154902.GA2964@alpha.arachsys.com> <64020C6E-98B1-4139-A88C-0EC65493CCF9@redhat.com> <560BEB14.3060701@redhat.com> <87si5vk0rz.fsf@notabene.neil.brown.name> <560D0668.50300@redhat.com> <87fv1m8ied.fsf@notabene.neil.brown.name> <5616586A.4000200@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3132938735685814031==" Return-path: In-Reply-To: <5616586A.4000200@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Heinz Mauelshagen , Brassow Jonathan , device-mapper development List-Id: dm-devel.ids --===============3132938735685814031== Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" --=-=-= Content-Type: text/plain Heinz Mauelshagen writes: > > E.g. keep track of the 'new' state of the array and initialize > parity/syndrome on first access to any given stripe with > the given performance optimization thereafter. > > Metadata kept to housekeep this could be organized in a b-tree > (e.g. via dm-persistent-data), thus storing just one node > defining the whole array as 'new' and splitting the tree up > as we go and have a size threshold to not allow to grow > such metadata too big. > This idea has come up before. A bitmap has been suggested. Simpler than a B-tree, though not as flexible. It would allows us to do something more meaningful with Discard: record that the whole region is invalid. I don't object to the idea, but I find it hard to get excited about. It further blurs the line between the filesystem and the storage device, and duplicates work between the two. NeilBrown --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJWFue5AAoJEDnsnt1WYoG5JUkP/iDZW3Ch9v3S0XSCm/a490ux Zyey5xlTe/77zbreE3VBFruJEUF2TsIDBBEjGTuTuDFSeKPTOe3dgnOBmPeSRZbn XG5rzDQR91WWFv21AGfthyHOAhm5DrThu70e6vqk1iJuRR32n777Qp9aJJaP80ib gndpbv8lsuNQPr1c+4CGvq+j8ydgb85HpwMM60UGq+i6hAo6YNYndOsdU7stMr6r pO3jHo1sTD+xi3oiK2vvhTXKsu72scnn9gj78x4NsJQDaO5exJNnfOPkiBmUHWAL lVOhGr8XqVJ+l2PwGfUm1lgdmJMcINUOoieupbdWUq90/TEjzGjB8JufZmuiDz8l YEN0IdEDgC+Fcd3u1aeDOwUURo76sEUocB482zKh7x9pJtDLNe8sx+gZoPUmlUB7 Qa5QXP9z2PLSCY28nwyIWlz0daxmSxvQFwcHcrdiYL8NY+T1Sn3GtlTPGTzwbpsR NPPl2CX5+ptSacrUkFZMiYvU9ttdlFUXZgnF+iGfaM/lglFktp8qfJUaEQCpfhd+ 2fh/JoIvnzml7p1KSEqweeSL4TJ5W2pPuRAsT9Iin1mzkGZ9LqOJHRVDNp7fPstA d4N2lgGn1Q+gu0u2fHKPEryCsEOPexBzjSb7XettRvcVfNB/bqErOfCgod7wvdXq spr8axofKs99uIXBVrx6 =ewng -----END PGP SIGNATURE----- --=-=-=-- --===============3132938735685814031== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline --===============3132938735685814031==--