[gpfsug-discuss] metadata replication question

[Barry Evans]

Can all 4 NSD servers see all existing storwize arrays across both DC's?

Cheers,
Barry


On 03/01/2016 21:56, Simon Thompson (Research Computing - IT Services) 
wrote:
> I currently have 4 NSD servers in a cluster, two pairs in two data centres. Data and metadata replication is currently set to 2 with metadata sitting on sas drivers in a storewise array. I also have a vm floating between the two data centres to guarantee quorum in one only in the event of split brain.
>
> Id like to add some ssd for metadata.
>
> Should I:
>
> Add raid1 ssd to the storewise?
>
> Add local ssd to the nsd servers?
>
> If I did the second, should I
>   add ssd to each nsd server (not raid 1) and set each in a different failure group and make metadata replication of 4.
>   add ssd to each nsd server as raid 1, use the same failure group for each data centre pair?
>   add ssd to each nsd server not raid 1, use the dame failure group for each data centre pair?
>
> Or something else entirely?
>
> What I want so survive is a split data centre situation or failure of a single nsd server at any point...
>
> Thoughts? Comments?
>
> I'm thinking the first of the nsd local options uses 4 writes as does the second, but each nsd server then has a local copy of the metatdata locally and ssd fails, in which case it should be able to get it from its local partner pair anyway (with readlocalreplica)?
>
> Id like a cost competitive solution that gives faster performance than the current sas drives.
>
> Was also thinking I might add an ssd to each nsd server for system.log pool for hawc as well...
>
> Thanks
>
> Simon
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-- 

Barry Evans
Technical Director & Co-Founder
Pixit Media
Mobile: +44 (0)7950 666 248
http://www.pixitmedia.com


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