Date: Wed, 17 Aug 2016 13:33:39 +0200 From: Julien Cigar <julien@perdition.city> To: InterNetX - Juergen Gotteswinter <juergen.gotteswinter@internetx.com> Cc: freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <20160817113339.GH22506@mordor.lan> In-Reply-To: <20160817095222.GG22506@mordor.lan> References: <20160704183643.GI41276@mordor.lan> <AE372BF0-02BE-4BF3-9073-A05DB4E7FE34@ixsystems.com> <20160704193131.GJ41276@mordor.lan> <E7D42341-D324-41C7-B03A-2420DA7A7952@sarenet.es> <20160811091016.GI70364@mordor.lan> <1AA52221-9B04-4CF6-97A3-D2C2B330B7F9@sarenet.es> <472bc879-977f-8c4c-c91a-84cc61efcd86@internetx.com> <20160817085413.GE22506@mordor.lan> <465bdec5-45b7-8a1d-d580-329ab6d4881b@internetx.com> <20160817095222.GG22506@mordor.lan>
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--qVHblb/y9DPlgkHs Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Aug 17, 2016 at 11:52:22AM +0200, Julien Cigar wrote: > On Wed, Aug 17, 2016 at 11:05:46AM +0200, InterNetX - Juergen Gotteswinte= r wrote: > >=20 > >=20 > > Am 17.08.2016 um 10:54 schrieb Julien Cigar: > > > On Wed, Aug 17, 2016 at 09:25:30AM +0200, InterNetX - Juergen Gottesw= inter wrote: > > >> > > >> > > >> Am 11.08.2016 um 11:24 schrieb Borja Marcos: > > >>> > > >>>> On 11 Aug 2016, at 11:10, Julien Cigar <julien@perdition.city> wro= te: > > >>>> > > >>>> As I said in a previous post I tested the zfs send/receive approac= h (with > > >>>> zrep) and it works (more or less) perfectly.. so I concur in all w= hat you > > >>>> said, especially about off-site replicate and synchronous replicat= ion. > > >>>> > > >>>> Out of curiosity I'm also testing a ZFS + iSCSI + CARP at the mome= nt,=20 > > >>>> I'm in the early tests, haven't done any heavy writes yet, but ATM= it=20 > > >>>> works as expected, I havent' managed to corrupt the zpool. > > >>> > > >>> I must be too old school, but I don=E2=80=99t quite like the idea o= f using an essentially unreliable transport > > >>> (Ethernet) for low-level filesystem operations. > > >>> > > >>> In case something went wrong, that approach could risk corrupting a= pool. Although, frankly, > > >>> ZFS is extremely resilient. One of mine even survived a SAS HBA pro= blem that caused some > > >>> silent corruption. > > >> > > >> try dual split import :D i mean, zpool -f import on 2 machines hooke= d up > > >> to the same disk chassis. > > >=20 > > > Yes this is the first thing on the list to avoid .. :) > > >=20 > > > I'm still busy to test the whole setup here, including the=20 > > > MASTER -> BACKUP failover script (CARP), but I think you can prevent > > > that thanks to: > > >=20 > > > - As long as ctld is running on the BACKUP the disks are locked=20 > > > and you can't import the pool (even with -f) for ex (filer2 is the > > > BACKUP): > > > https://gist.github.com/silenius/f9536e081d473ba4fddd50f59c56b58f > > >=20 > > > - The shared pool should not be mounted at boot, and you should ensure > > > that the failover script is not executed during boot time too: this is > > > to handle the case wherein both machines turn off and/or re-ignite at > > > the same time. Indeed, the CARP interface can "flip" it's status if b= oth > > > machines are powered on at the same time, for ex: > > > https://gist.github.com/silenius/344c3e998a1889f988fdfc3ceba57aaf and > > > you will have a split-brain scenario > > >=20 > > > - Sometimes you'll need to reboot the MASTER for some $reasons > > > (freebsd-update, etc) and the MASTER -> BACKUP switch should not > > > happen, this can be handled with a trigger file or something like that > > >=20 > > > - I've still have to check if the order is OK, but I think that as lo= ng > > > as you shutdown the replication interface and that you adapt the > > > advskew (including the config file) of the CARP interface before the= =20 > > > zpool import -f in the failover script you can be relatively confiden= t=20 > > > that nothing will be written on the iSCSI targets > > >=20 > > > - A zpool scrub should be run at regular intervals > > >=20 > > > This is my MASTER -> BACKUP CARP script ATM > > > https://gist.github.com/silenius/7f6ee8030eb6b923affb655a259bfef7 > > >=20 > > > Julien > > >=20 > >=20 > > 100=E2=82=AC question without detailed looking at that script. yes from= a first > > view its super simple, but: why are solutions like rsf-1 such more > > powerful / featurerich. Theres a reason for, which is that they try to > > cover every possible situation (which makes more than sense for this). >=20 > I've never used "rsf-1" so I can't say much more about it, but I have=20 > no doubts about it's ability to handle "complex situations", where=20 > multiple nodes / networks are involved. BTW for simple cases (two nodes, same network, one active node, ...) we could use both: ZFS + iSCSI + CARP on the two nodes, and=20 zfs send|zfs receive on a third one >=20 > >=20 > > That script works for sure, within very limited cases imho > >=20 > > >> > > >> kaboom, really ugly kaboom. thats what is very likely to happen soon= er > > >> or later especially when it comes to homegrown automatism solutions. > > >> even the commercial parts where much more time/work goes into such > > >> solutions fail in a regular manner > > >> > > >>> > > >>> The advantage of ZFS send/receive of datasets is, however, that you= can consider it > > >>> essentially atomic. A transport corruption should not cause trouble= (apart from a failed > > >>> "zfs receive") and with snapshot retention you can even roll back. = You can=E2=80=99t roll back > > >>> zpool replications :) > > >>> > > >>> ZFS receive does a lot of sanity checks as well. As long as your zf= s receive doesn=E2=80=99t involve a rollback > > >>> to the latest snapshot, it won=E2=80=99t destroy anything by mistak= e. Just make sure that your replica datasets > > >>> aren=E2=80=99t mounted and zfs receive won=E2=80=99t complain. > > >>> > > >>> > > >>> Cheers, > > >>> > > >>> > > >>> > > >>> > > >>> Borja. > > >>> > > >>> > > >>> > > >>> _______________________________________________ > > >>> freebsd-fs@freebsd.org mailing list > > >>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs > > >>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.or= g" > > >>> > > >> _______________________________________________ > > >> freebsd-fs@freebsd.org mailing list > > >> https://lists.freebsd.org/mailman/listinfo/freebsd-fs > > >> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > > >=20 >=20 > --=20 > Julien Cigar > Belgian Biodiversity Platform (http://www.biodiversity.be) > PGP fingerprint: EEF9 F697 4B68 D275 7B11 6A25 B2BB 3710 A204 23C0 > No trees were killed in the creation of this message. > However, many electrons were terribly inconvenienced. --=20 Julien Cigar Belgian Biodiversity Platform (http://www.biodiversity.be) PGP fingerprint: EEF9 F697 4B68 D275 7B11 6A25 B2BB 3710 A204 23C0 No trees were killed in the creation of this message. 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