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Question about stacking InfiniBand switches ?

chuckk281
Trusted Contributor

Question about stacking InfiniBand switches ?

Rob had an InfiniBand question:

 

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Does anyone know if stacking IB switches from enclosure to enclosure is supported ?

 

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Good responses:

 

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Keith replied:

Hi Robert, page 7 of this doc shows two c7000 enclosures directly linked using IB - http://h20195.www2.hp.com/V2/GetPDF.aspx/4AA2-2519ENW.pdf

 

My understanding on IB in c7000 environments (from Oracle RAC) is:

 

  • The c7000’s internal IB switches cannot manage the IB fabric – they are “dumb”.

 

  • You need an IB fabric manager – it can be software or hardware based – latter recommended (similar to hardware RAID or software mirroring choices for storage).

 

  • I typically propose a pair of “intelligent” external IB switches, to manage the IB fabric – these external switches are used to link the c7000’s internal IB switches together.

 

I hope this helps! Regards!

 

Andrey also chimed in:

Hello Robert,

 

Yes – you can connect 2x c-class IB switches directly

 

But for more than 2x blade IB switches you must use external IB switches – to build Fat-Tree (CLOS) topology

 

Very important -  as Keith mentioned – for Infiniband fabric you need an SM (Subnet Manager) - host based or embedded in hardware

 

Mellanox based c-class switches (like 489184-B21) have no embedded HW SM – so you must use free OpenSM or Commercial UFM  or external switch with management (check if local HPS or customer have enough expertise for SW solution)

 

Qlogic based c-class switches (505958-B21) can be managed by host-based SW Subnet Manager,  or you may propose HW SM module (505959-B21)

 

PS Check QuickSpec at http://h18000.www1.hp.com/products/quickspecs/13078_div/13078_div.html

 

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Any other advice for Rob?