Re: [Xen-users] SAS drivers that work reliably under Xen

[Håkon Alstadheim <hakon@xxxxxxxxxxxxxxxxxx>]

Den 16. jan. 2017 14:29, skrev Andy Smith:
> Hi,
> 
> Could any of you recommend SAS drivers which you have working
> reliably in Xen dom0?
> 
> I have a Supermicro X10SRH-CLN4F board which has an LSI 3008
> controller on-board; this uses the mpt3sas driver.
> 
> Unfortunately it is unusable under Xen (works fine bare metal).
> There are patches to fix it, but these have been rejected by
> upstream Linux so it could be a very long time before any resolution
> is found. More details here:
> 
>     https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=850425
> 
> I am probably going to find it easier and quicker to just buy a
> different board, if I can find one with a well-supported SAS
> chipset. I am assuming there must be some as otherwise we'd have
> heard about such a massive problem by now.
> 
> So, those of you that have SAS, which chipset and drivers are you
> using?
> 

Privately, I'm running RAID bus controller: LSI Logic / Symbios Logic
MegaRAID SAS 2008, with megaraid_sas kernel module. Had some issues a
couple of years ago, gone now, after some firmware updates. Not the
newest and most bleeding edge, but then I get to not bleed :-) . I
believe the LSI card is the reason why I have
"iommu_inclusive_mapping=1" on my xen command-line.

Running Xen-4.9.4 with dom0 "Linux gentoo 4.9.4-gentoo" at the moment.
Card has been stable since xen-4.6, linux 4.1. (after the iommu tweak
and firmware updates mentioned ) .

I'm NOT getting bare-metal speeds though. Had to get an ssd and run it
as bcache to avoid issues with media (streaming in and out of various
VMs simultaneously ) and database servers (that also require
near-real-time response). Must say I'm quite happy with bcache. Tweaked
the logical volumes with partitioning to make the bcache backing fall on
a raid stripe boundary, since it seems bcache ignores that kind of info,
or at least fails to propagate it to the bcache volumes that the domUs
live on.

Running the card mostly as straight JBOD, only one pair in RAID1 is the
exception. Using linux md-raid and lvm on top of that (in dom0), bcache
on top of selected logical volumes (also in dom0).


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