3:49 a.m.
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On 09/09/2015 10=3A14 AM=2C Richard Neuboeck wrote=3A
=3E On 04=2E09=2E15 10=3A02=2C Simone Tiraboschi wrote=3A
=3E=3E Is there a reason why it has to be exactly replica 3=3F
=3E=3E
=3E=3E
=3E=3E To have a valid quorum having the system being able to decide witch=
is
=3E=3E the right and safe copy avoiding an issue called split brain=2E
=3E=3E Under certain circumstances/issues =28network issue=2C hosts down or=
=3E=3E whatever could happen=29 the data on different replica could diverge=
=3A if
=3E=3E you have two and just two different hosts that claim each other
=3E that its
=3E=3E copy is the right one there is no way to automatically take the righ=
t
=3E=3E decision=2E Having three hosts and setting the quorum according to t=
hat
=3E=3E solves/mitigates the issue=2E
=3E
=3E Thanks for the explanation=2E I do understand the problem but since
=3E I=27m somewhat limited in my hardware options is there a way to
=3E override this requirement=3F Meaning if I change the checks for
=3E replica 3 in the installation scripts does something else fail on
=3E the way=3F
=3E
=3E In my case coherence checks would come from outside the storage and
=3E vm host setup and fencing would be applied appropriately=2E
=3E
=3E I would very much appreciate it if the particulars of the storage
=3E setup could be either selected from a list of possibilities or be
=3E ignored and just a warning be issued that this setup is not recommended=
=2E
=3E
=3E Thanks!
=3E Richard
=3E
=3E
As a side question=2C in Glusterfs 3=2E7 there is an =22AFR arbiter volume=
=22
=28http=3A//gluster=2Ereadthedocs=2Eorg/en/release-3=2E7=2E0-1/Features/afr=
-arbiter-volumes/=29
that will only contain the metadata=2E
Will ovirt support this in 3=2E6=3F
Kind regards=2C
Jorick Astrego
Met vriendelijke groet=2C With kind regards=2C
Jorick Astrego
Netbulae Virtualization Experts=20
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08198180
=09Fax=3A 053 20 30 271 =09www=2Enetbulae=2Eeu =097547 TA Enschede =09BTW=
NL821234584B01
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<br <br On 09/09/2015 10:14 AM, Richard Neuboeck
wrote: <br <font
color=3D"#000000">> On 04.09.15 10:02, Simone Tiraboschi
wrote:=
3;</font><br <font
color=3D"#000000">>> Is
there a reason =
why it has to be exactly replica 3? </font><br <font
color=3D"#000000">>> </font><br <font
color=3D"#000000">>> </font><br <font color=3D"#000000">>> To
have a valid quorum having the system b=
eing able to decide witch is </font><br <font
color=3D"#000000">>> the right and safe copy avoiding an issue
=
called split brain. </font><br <font
color=3D"#000000">>> Under certain circumstances/issues
(networ=
k issue, hosts down or </font><br <font
color=3D"#000000">>> whatever could happen) the data on
differe=
nt replica could diverge: if </font><br <font
color=3D"#000000">>> you have two and just two different hosts
=
that claim each other </font><br <font
color=3D"#000000">> that its </font><br <font color=3D"#000000">>> copy
is the right one there is no way to a=
utomatically take the right </font><br <font
color=3D"#000000">>> decision. Having three hosts and setting
t=
he quorum according to that </font><br <font
color=3D"#000000">>> solves/mitigates the
issue. </font><br=
<font
color=3D"#000000">> </font><br <font color=3D"#000000">> Thanks for the
explanation. I do understand th=
e problem but since </font><br <font
color=3D"#000000">> I'm somewhat limited in my hardware options
is=
there a way to </font><br <font
color=3D"#000000">> override this requirement? Meaning if I change=
the checks for </font><br <font
color=3D"#000000">> replica 3 in the installation scripts does som=
ething else fail on </font><br <font
color=3D"#000000">> the way? </font><br <font
color=3D"#000000">> </font><br <font color=3D"#000000">> In my case
coherence checks would come from ou=
tside the storage and </font><br <font
color=3D"#000000">> vm host setup and fencing would be applied app=
ropriately. </font><br <font
color=3D"#000000">> </font><br <font color=3D"#000000">> I would very
much appreciate it if the particu=
lars of the storage </font><br <font
color=3D"#000000">> setup could be either selected from a list of =
possibilities or be </font><br <font
color=3D"#000000">> ignored and just a warning be issued that this=
setup is not recommended. </font><br <font
color=3D"#000000">> </font><br <font color=3D"#000000">>
Thanks! </font><br <font
color=3D"#000000">> Richard </font><br <font
color=3D"#000000">> </font><br <font
color=3D"#000000">> </font><br As a side question, in Glusterfs 3.7 there is an "AFR
arbiter volume&q=
uot; <br (<a
href=3D"http://gluster.readthedocs.org/en/release-3.7.0-1/Features/a...
arbiter-volumes/">http://gluster.readthedocs.org/en/release-3.7.0...
s/afr-arbiter-volumes/</a>) <br that will
only contain the metadata. <br
<br Will ovirt support this in
3.6? <br <br Kind regards, <br
<br Jorick Astrego <br =
=3CBR /=3E
=3CBR /=3E
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