HAST + ZFS + NFS + CARP

Thu Aug 18 07:34:17 UTC 2016

Am 17.08.2016 um 23:14 schrieb Ben RUBSON:
> 
>> On 17 Aug 2016, at 20:03, Linda Kateley <lkateley at kateley.com> wrote:
>>
>> RSF-1 runs in the zfs stack and send the writes to the second system.
> 
> Linda, do you have any link to a documentation about this RSF-1 operation mode ?
> 
> According to what I red about RSF-1, storage is shared between nodes, and RSF-1 manages the failover, we do not have 2 different storages.
> (so I don't really understand how writes are sent to the "second system")

yes this is how i know rsf-1, too. external cross cabled sas jbods
hooked up to two headnodes. it all works (or fails) if activating /
disabling of sas channels works like expected.

> 
> In addition, RSF-1 does not seem to help with long-distance replication to a different storage.

i think theres something called metro replication, but did not dig
further into that. might be part of nexenta

> But I may be wrong ?
> This is where ZFS send/receive helps.
> Or even a nicer solution I proposed a few weeks ago : https://www.illumos.org/issues/7166 (but a lot of work to achieve).
> 
> Ben
> 
>> On 8/17/16 11:55 AM, Chris Watson wrote:
>>> Of course, if you are willing to accept some amount of data loss that opens up a lot more options. :)
>>>
>>> Some may find that acceptable though. Like turning off fsync with PostgreSQL to get much higher throughput. As little no as you are made *very* aware of the risks.
>>>
>>> It's good to have input in this thread from one with more experience with RSF-1 than the rest of us. You confirm what others have that said about RSF-1, that it's stable and works well. What were you deploying it on?
>>>
>>> Chris
>>>
>>> Sent from my iPhone 5
>>>
>>> On Aug 17, 2016, at 11:18 AM, Linda Kateley <lkateley at kateley.com <mailto:lkateley at kateley.com>> wrote:
>>>
>>>> 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 at perdition.city <mailto:julien at 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 at freebsd.org <mailto:freebsd-fs at freebsd.org> mailing list
>>>>>>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
>>>>>>>>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org <mailto:freebsd-fs-unsubscribe at freebsd.org>"
>>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> freebsd-fs at freebsd.org <mailto:freebsd-fs at freebsd.org> mailing list
>>>>>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
>>>>>>>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org <mailto:freebsd-fs-unsubscribe at freebsd.org>"
>>>>
>>>> _______________________________________________
>>>> freebsd-fs at freebsd.org <mailto:freebsd-fs at freebsd.org> mailing list
>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
>>>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org <mailto:freebsd-fs-unsubscribe at freebsd.org>"
>>
>> _______________________________________________
>> freebsd-fs at freebsd.org mailing list
>> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org"
> 
> _______________________________________________
> freebsd-fs at freebsd.org mailing list
> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org"
> 