[ovirt-users] [GlusterFS] Regarding gluster backup-volfile-servers option

[TranceWorldLogic .]

Hi,

Can you point me to some document that help me to understand how gluster
client work ?
Related to ovirt will be helpful.

Thanks,
~Rohit

On Thu, May 18, 2017 at 11:54 AM, knarra <knarra at redhat.com> wrote:

> On 05/18/2017 10:35 AM, TranceWorldLogic . wrote:
>
> Thanks,
> Would you also explain about my 2nd question ?
>
> let say hostB mounted glusterFS partition by using backup vol (e.g. hostB)
> and after some time Host A come online, will GlusterFS client (mount)
> automatically switch to Host A ?
>
> mount will not switch automatically to Host A .
>
> In an ideal case i.e with out using backup-vol-file-server option if host
> B goes down, you mount will not be accessible since host B went down and df
> -TH or mount does not show the volume or it says "Transport End point not
> connected".
>
> Take the case where using backup-volfile-server option. If host B goes
> down, your mount will still be accessible since there is
> backup-volfile-server and df -TH or mount still shows that volume is
> mounted using Host B, but all the internal requests will be served through
> Host A.
>
>
>
> On Thu, May 18, 2017 at 9:43 AM, knarra <knarra at redhat.com> wrote:
>
>> Hi,
>>
>>     backup-volfile-servers is mainly used to avoid SPOF. For example take
>> a scenario where you have Host A and Host B and when you try to mount a
>> glusterfs volume using Host A with backup-volfile-servers specified, if
>> Host A is not accessible, mount will happen with Host B which is specified
>> in backup-volfile-server. backup-volfile-servers are mainly used to fetch
>> the volfile from gluster and  has nothing to do with data sync.
>>
>>     data syncing comes as part of replicate feature in glusterfs where
>> say for example, you have two Hosts Host A and Host B with replica volume
>> configured, if Host A goes down for sometime, all the writes happens on
>> Host B and when Host A comes up data gets synced to HostA.
>>
>> Hope this helps !!!!
>>
>> Thanks
>> kasturi
>>
>>
>> On 05/17/2017 11:31 PM, TranceWorldLogic . wrote:
>>
>> Hi,
>>
>> Before trying out, I want to understand how glusterfs will react for
>> below scenario.
>> Please help me.
>>
>> Let consider I have two host hostA and hostB
>> I have setup replica volume on hostA and hostB. (consider as storage
>> domain for DATA in ovirt).
>> I have configure data domain mount command with backup server option
>> (backup-volfile-server) as hostB (I mean main server as hostA and backup as
>> hostB)
>>
>> 1> As I understood, VDSM execute mount command on both hostA and
>> hostB.(for creating data domain)
>> 2> That mean, HostB glusterFS CLIENT will communicate with main server
>> (hostA).
>> (Please correct me if I am wrong here.)
>> 3> Let say HostA got down (say shutdown, power off scenario)
>> 4> Due to backup option I will have data domain available on HostB.
>> (Now glusterFS CLIENT on HostB will start communicating with HostB
>> GlusterFS SERVER).
>> 5> Now let say HostA comes up.
>> 6> Will it sync all data from HostB to HostA glusterFS server ?
>> (as per doc, yes, i not tried yet, want to confirm my understanding)
>> 7> Will glusterFS CLIENT on HostB start communicate with main server
>> (HostA) ?
>>
>> Please let me know, I am new to glusterFS.
>>
>> Thanks,
>> ~Rohit
>>
>>
>> _______________________________________________
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>>
>>
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