Date: Wed, 17 Aug 2016 11:18:42 -0500 From: Linda Kateley <lkateley@kateley.com> To: freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <52d5b687-1351-9ec5-7b67-bfa0be1c8415@kateley.com> In-Reply-To: <20160817095222.GG22506@mordor.lan> 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> <20160817095222.GG22506@mordor.lan>
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The question I always ask, as an architect, is "can you lose 1 minute worth of data?" If you can, then batched replication is perfect. If you can't.. then HA. Every place I have positioned it, rsf-1 has worked extremely well. If i remember right, it works at the dmu. I would suggest try it. They have been trying to have a full freebsd solution, I have several customers running it well. linda On 8/17/16 4:52 AM, Julien Cigar wrote: > On Wed, Aug 17, 2016 at 11:05:46AM +0200, InterNetX - Juergen Gotteswinter wrote: >> >> Am 17.08.2016 um 10:54 schrieb Julien Cigar: >>> On Wed, Aug 17, 2016 at 09:25:30AM +0200, InterNetX - Juergen Gotteswinter 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 what you >>>>>> said, especially about off-site replicate and synchronous replication. >>>>>> >>>>>> Out of curiosity I'm also testing a ZFS + iSCSI + CARP at the moment, >>>>>> I'm in the early tests, haven't done any heavy writes yet, but ATM it >>>>>> works as expected, I havent' managed to corrupt the zpool. >>>>> I must be too old school, but I don’t 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 pool. Although, frankly, >>>>> ZFS is extremely resilient. One of mine even survived a SAS HBA problem 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. >>> Yes this is the first thing on the list to avoid .. :) >>> >>> I'm still busy to test the whole setup here, including the >>> MASTER -> BACKUP failover script (CARP), but I think you can prevent >>> that thanks to: >>> >>> - As long as ctld is running on the BACKUP the disks are locked >>> and you can't import the pool (even with -f) for ex (filer2 is the >>> BACKUP): >>> https://gist.github.com/silenius/f9536e081d473ba4fddd50f59c56b58f >>> >>> - 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 >>> >>> - 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 >>> >>> - 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 >>> zpool import -f in the failover script you can be relatively confident >>> that nothing will be written on the iSCSI targets >>> >>> - A zpool scrub should be run at regular intervals >>> >>> This is my MASTER -> BACKUP CARP script ATM >>> https://gist.github.com/silenius/7f6ee8030eb6b923affb655a259bfef7 >>> >>> Julien >>> >> 100€ 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 > no doubts about it's ability to handle "complex situations", where > multiple nodes / networks are involved. > >> That script works for sure, within very limited cases imho >> >>>> 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 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’t roll back >>>>> zpool replications :) >>>>> >>>>> ZFS receive does a lot of sanity checks as well. As long as your zfs receive doesn’t involve a rollback >>>>> to the latest snapshot, it won’t destroy anything by mistake. Just make sure that your replica datasets >>>>> aren’t mounted and zfs receive won’t 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"
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