Date: Thu, 30 Jun 2016 17:37:47 +0200 From: Julien Cigar <julien@perdition.city> To: Ben RUBSON <ben.rubson@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <20160630153747.GB5695@mordor.lan> In-Reply-To: <AD42D8FD-D07B-454E-B79D-028C1EC57381@gmail.com> References: <20160630144546.GB99997@mordor.lan> <71b8da1e-acb2-9d4e-5d11-20695aa5274a@internetx.com> <AD42D8FD-D07B-454E-B79D-028C1EC57381@gmail.com>
index | next in thread | previous in thread | raw e-mail
[-- Attachment #1 --] On Thu, Jun 30, 2016 at 05:28:41PM +0200, Ben RUBSON wrote: > > > On 30 Jun 2016, at 17:14, InterNetX - Juergen Gotteswinter <jg@internetx.com> wrote: > > > > > > > > Am 30.06.2016 um 16:45 schrieb Julien Cigar: > >> Hello, > >> > >> I'm always in the process of setting a redundant low-cost storage for > >> our (small, ~30 people) team here. > >> > >> I read quite a lot of articles/documentations/etc and I plan to use HAST > >> with ZFS for the storage, CARP for the failover and the "good old NFS" > >> to mount the shares on the clients. > >> > >> The hardware is 2xHP Proliant DL20 boxes with 2 dedicated disks for the > >> shared storage. > >> > >> Assuming the following configuration: > >> - MASTER is the active node and BACKUP is the standby node. > >> - two disks in each machine: ada0 and ada1. > >> - two interfaces in each machine: em0 and em1 > >> - em0 is the primary interface (with CARP setup) > >> - em1 is dedicated to the HAST traffic (crossover cable) > >> - FreeBSD is properly installed in each machine. > >> - a HAST resource "disk0" for ada0p2. > >> - a HAST resource "disk1" for ada1p2. > >> - a zpool create zhast mirror /dev/hast/disk0 /dev/hast/disk1 is created > >> on MASTER > >> > >> A couple of questions I am still wondering: > >> - If a disk dies on the MASTER I guess that zpool will not see it and > >> will transparently use the one on BACKUP through the HAST ressource.. > > > > thats right, as long as writes on $anything have been successful hast is > > happy and wont start whining > > > >> is it a problem? > > > > imho yes, at least from management view > > > >> could this lead to some corruption? > > > > probably, i never heard about anyone who uses that for long time in > > production > > > > At this stage the > >> common sense would be to replace the disk quickly, but imagine the > >> worst case scenario where ada1 on MASTER dies, zpool will not see it > >> and will transparently use the one from the BACKUP node (through the > >> "disk1" HAST ressource), later ada0 on MASTER dies, zpool will not > >> see it and will transparently use the one from the BACKUP node > >> (through the "disk0" HAST ressource). At this point on MASTER the two > >> disks are broken but the pool is still considered healthy ... What if > >> after that we unplug the em0 network cable on BACKUP? Storage is > >> down.. > >> - Under heavy I/O the MASTER box suddently dies (for some reasons), > >> thanks to CARP the BACKUP node will switch from standy -> active and > >> execute the failover script which does some "hastctl role primary" for > >> the ressources and a zpool import. I wondered if there are any > >> situations where the pool couldn't be imported (= data corruption)? > >> For example what if the pool hasn't been exported on the MASTER before > >> it dies? > >> - Is it a problem if the NFS daemons are started at boot on the standby > >> node, or should they only be started in the failover script? What > >> about stale files and active connections on the clients? > > > > sometimes stale mounts recover, sometimes not, sometimes clients need > > even reboots > > > >> - A catastrophic power failure occur and MASTER and BACKUP are suddently > >> powered down. Later the power returns, is it possible that some > >> problem occur (split-brain scenario ?) regarding the order in which the > > > > sure, you need an exact procedure to recover > > > >> two machines boot up? > > > > best practice should be to keep everything down after boot > > > >> - Other things I have not thought? > >> > > > > > > > >> Thanks! > >> Julien > >> > > > > > > imho: > > > > leave hast where it is, go for zfs replication. will save your butt, > > sooner or later if you avoid this fragile combination > > I was also replying, and finishing by this : > Why don't you set your slave as an iSCSI target and simply do ZFS mirroring ? Yes that's another option, so a zpool with two mirrors (local + exported iSCSI) ? > ZFS would then know as soon as a disk is failing. > And if the master fails, you only have to import (-f certainly, in case of a master power failure) on the slave. > > Ben > > _______________________________________________ > 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" -- 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. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCgAGBQJXdTzLAAoJELK7NxCiBCPAU+EP/2sN1DkF36296xw1+mRA0dIz rqyGM7fBZOhHCSqZ7YzzCKvpb28Pg5qe+oMD/tJ2N0sp5O07nG84sYMGFqEAirE1 LZaDoiMItRYobsIFpNjrMagmX5l9kiMy1aFo//eTFfY/J6Bzka2m7kErOtuhOkiP gp7r02Rsr3dztjAa60Mpo0XYv2A9AOa2KkNJ0wQm2vdzXjzFIYomGvK7Eg0cDdMH cfZWVSEDl5LundgtX7b1NY8gG04eP7c2lgOUTBO++D5p4SjzwZ07px56tSX9pqP1 TMG38CtUmA0w0MDDdXE6KiFg0ZYmFPQSmmV1SD/O34iuP1wo4BkIiOPf7lIYoxYQ O/TZbD8VKbYAEKNChpTjFlKgGYFKPLK1IL3H6x0G4UtLC2SnUFlel4eH5LvZmlvz hhTpjX9Ybjdn3Y4YXbnCr02rhwacapVghnwJQ8kjPHp/azLtAI7eyHtMWdZv2m2I fxGw3npMM1CgF0xCF56CdM8t4XyqD5XMyU2RCYFNeTx/5t7MbjktCdK53QDlxHT9 3kuGYJG6MhLdjXuedl1QFyb91x3di7BjNDxt0qmrIMCsjO58J+0GOGmP5Te/sBlA vWYMkfwKcX8lNuqT3xKESrclBofyboGsFRQBK5tbnCkfQEr4w4AlpVM3SPH7LspV wYacJIrWBrAlEAunATQ8 =OY/+ -----END PGP SIGNATURE-----help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20160630153747.GB5695>