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Question about stacking InfiniBand switches ?

Trusted Contributor

Question about stacking InfiniBand switches ?

Rob had an InfiniBand question:




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




Good responses:




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




Any other advice for Rob?