Hi Joe,
Thanks for getting back to me about this, it was helpful, and I really
appreciate it.
I am, however, still (slightly) confused - *how* does the client
"know"
the addresses of the other servers in the cluster (for read or write
purposes), when all the client has is the line in the fstab file:
"gfs1:gv1? /data/gv1? glusterfs defaults? 0 2"? I'm missing
something,
somewhere, in all of this, and I can't work out what that
"something"
is.? :-)
Your help truely is appreciated
Cheers
Dulux-Oz
PEREGRINE IT Signature On 01/09/2022 00:55, Joe Julian
wrote:>
> With a replica volume the client connects and writes to all the
> replicas directly. For reads, when a filename is looked up the client
> checks with all the replicas and, if the file is healthy, opens a read
> connection to the first replica to respond (by default).
>
> If a server is shut down, the client receives the tcp messages that
> close the connection. For read operations, it chooses the next server.
> Writes will just continue to the remaining replicas (metadata is
> stored in extended attributes to inform future lookups and the
> self-healer of file health).
>
> If a server crashes (no tcp finalization) the volume will pause for
> ping-timeout seconds (42 by default). Then continue as above. BTW,
> that 42 second timeout shouldn't be a big deal. The MTBF should be
> sufficiently far apart that this should still easily get you five or
> six nines.
>
> On 8/30/22 11:55 PM, duluxoz wrote:
>>
>> Hi Guys & Gals,
>>
>> A Gluster newbie question for sure, but something I just don't
"get"
>> (or I've missed in the doco, mailing lists, etc):
>>
>> What happens to a Gluster Client when a Gluster Cluster Node goes
>> off-line / fails-over?
>>
>> How does the Client "know" to use (connect to) another
Gluster Node
>> in the Gluster Cluster?
>>
>> Let me elaborate.
>>
>> I've got four hosts: gfs1, gfs2, gfs3, and client4 sitting on
>> 192.168.1.1/24, .2, .3, and .4 respectively.
>>
>> DNS is set up and working correctly.
>>
>> gfs1, gs2, and gfs3 form a "Gluster Cluster" with a Gluster
Volume
>> (gv1) replicated across all three nodes. This is all working
>> correctly (ie a file (file1) created/modified on gfs1:/gv1 is
>> replicated correctly to gfs2:/gv1 and gfs3:/gv1).
>>
>> client4 has an entry in its /etc/fstab file which reads:
"gfs1:gv1?
>> /data/gv1 glusterfs? defaults? 0 2". This is also all working
>> correctly (ie client4:/data/gv1/file1 is accessible and replicated).
>>
>> So, (and I haven't tested this yet) what happens to
>> client4:/data/gv1/file1 when gfs1 fails (ie is turned off, crashes,
etc)?
>>
>> Does client4 "automatically" switch to using one of the other
two
>> Gluster Nodes, or do I have something wrong in clients4's
/etc/fstab
>> file, or an error/mis-configuration somewhere else?
>>
>> I thought about setting some DNS entries along the lines of:
>>
>> ~~~
>>
>> glustercluster? IN? A 192.168.0.1
>>
>> glustercluster? IN? A? 192.168.0.2
>>
>> glustercluster IN? A? 192.168.0.3
>>
>> ~~~
>>
>> and having clients4's /etc/fstab file read:
"glustercluster:gv1?
>> /data/gv1? glusterfs? defaults? 0 2", but this is a Round-Robin
DNS
>> config and I'm not sure how Gluster treats this situation.
>>
>> So, if people could comment / point me in the correct direction I
>> would really appreciate it - thanks.
>>
>> Dulux-Oz
>>
>>
>> ________
>>
>>
>>
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>>
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