Date: Fri, 1 Jul 2016 13:58:42 +0200 From: Ben RUBSON <ben.rubson@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <5F99508D-7532-468A-9121-7A76957A72DB@gmail.com> In-Reply-To: <5776569B.3050504@quip.cz> References: <71b8da1e-acb2-9d4e-5d11-20695aa5274a@internetx.com> <AD42D8FD-D07B-454E-B79D-028C1EC57381@gmail.com> <20160630153747.GB5695@mordor.lan> <63C07474-BDD5-42AA-BF4A-85A0E04D3CC2@gmail.com> <20160630163541.GC5695@mordor.lan> <50BF1AEF-3ECC-4C30-B8E1-678E02735BB5@gmail.com> <20160701084717.GE5695@mordor.lan> <47c7e1a5-6ae8-689c-9c2d-bb92f659ea43@internetx.com> <20160701101524.GF5695@mordor.lan> <f74627e3-604e-da71-c024-7e4e71ff36cb@internetx.com> <20160701105735.GG5695@mordor.lan> <5776569B.3050504@quip.cz>
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> On 01 Jul 2016, at 13:40, Miroslav Lachman <000.fbsd@quip.cz> wrote: >=20 > Julien Cigar wrote on 07/01/2016 12:57: >=20 >>>> why...? I guess iSCSI is slower but should be safer than HAST, no? >>>=20 >>> do your testing, please. even with simulated short network cuts. = 10-20 >>> secs are way enaugh to give you a picture of what is going to happen >>=20 >> of course I'll test everything properly :) I don't have the hardware = yet >> so ATM I'm just looking for all the possible "candidates", and I'm >> aware that a redundant storage is not that easy to implement ... >>=20 >> but what solutions do we have? It's either CARP + ZFS + (HAST|iSCSI), >> either zfs send|ssh zfs receive as you suggest (but it's >> not realtime), either a distributed FS (which I avoid like the = plague..) >=20 > When disaster comes you will need to restart NFS clients in almost all = cases (with CARP + ZFS + HAST|iSCSI) and you will lose some writes too. > And if something bad happens with your mgmt scripts or network you can = end up with corrupted ZFS pool on master and slave too - you will need = to recovery from backups. For example in some split brain scenario when = both nodes will try to import pool. Of course you must take care that both nodes do not import the pool at = the same time. For the slave to import the pool, first stop iSCSI targets (ctld), and = also put network replication interface down, to be sure. Then, import the pool. Once old master repaired, export its pool (if still imported), make its = disks iSCSI targets and give them the old slave (promoted master just = above). Of course it implies some meticulous administration. > With ZFS send & receive you will lose some writes but the chance you = will corrupt both pools are much lower than in the first case and the = setup is much simpler and runtime error proof. Only some ? Depending on the write throughput, won't you loose a lot of data on the = target/slave ? How do you make ZFS send/receive quite realtime ? while [ 1 ] do ; snapshot ; send/receive ; delete old snapshots ; done ? Thanks !=
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