Date: Wed, 17 Aug 2016 11:52:22 +0200 From: Julien Cigar <julien@perdition.city> To: InterNetX - Juergen Gotteswinter <juergen.gotteswinter@internetx.com> Cc: Borja Marcos <borjam@sarenet.es>, freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <20160817095222.GG22506@mordor.lan> In-Reply-To: <465bdec5-45b7-8a1d-d580-329ab6d4881b@internetx.com> References: <61283600-A41A-4A8A-92F9-7FAFF54DD175@ixsystems.com> <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>
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--I3tAPq1Rm2pUxvsp Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Aug 17, 2016 at 11:05:46AM +0200, InterNetX - Juergen Gotteswinter = 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 Gotteswin= ter wrote: > >> > >> > >> Am 11.08.2016 um 11:24 schrieb Borja Marcos: > >>> > >>>> On 11 Aug 2016, at 11:10, Julien Cigar <julien@perdition.city> wrote: > >>>> > >>>> As I said in a previous post I tested the zfs send/receive approach = (with > >>>> zrep) and it works (more or less) perfectly.. so I concur in all wha= t you > >>>> said, especially about off-site replicate and synchronous replicatio= n. > >>>> > >>>> Out of curiosity I'm also testing a ZFS + iSCSI + CARP at the moment= ,=20 > >>>> I'm in the early tests, haven't done any heavy writes yet, but ATM i= t=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 of = using an essentially unreliable transport > >>> (Ethernet) for low-level filesystem operations. > >>> > >>> In case something went wrong, that approach could risk corrupting a p= ool. Although, frankly, > >>> ZFS is extremely resilient. One of mine even survived a SAS HBA probl= em that caused some > >>> silent corruption. > >> > >> try dual split import :D i mean, zpool -f import on 2 machines hooked = 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 both > > 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 long > > 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 confident= =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). 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. >=20 > That script works for sure, within very limited cases imho >=20 > >> > >> kaboom, really ugly kaboom. thats what is very likely to happen sooner > >> 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 c= an 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. Yo= u can=E2=80=99t roll back > >>> zpool replications :) > >>> > >>> ZFS receive does a lot of sanity checks as well. As long as your zfs = receive doesn=E2=80=99t involve a rollback > >>> to the latest snapshot, it won=E2=80=99t destroy anything by mistake.= 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.org" > >>> > >> _______________________________________________ > >> 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 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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