Re: [SSI-users] debian lenny stability, reliability, xen, drbd?

[John H. <jo...@Ca...>]

jhonyl wrote:
> Hi,
>
> I am thinking about an OpenSSI two nodes cluster with mirrored disks
> between the nodes, probably using drbd. I need an uptodate desktop
> environment, and high availability.
>
>
> I would like to know how stable and reliable is the OpenSSI for lenny.
> Seeing that it is being kept in the directory called alpha got me a bit
> worried, since I would like this server to operate without an admin
> babysitting it.
>   
Frankly OpenSSI is currently not as stable as it could be, though it's 
getting better.   With an OpenSSI-HA setup you'll definitely be better 
protected against hardware problems, but you likely to run into more 
problems caused by the software.

However the real reasons I consider my OpenSSI Lenny port "alpha" 
quality are:

   1. The kernel is my port of the latest OpenSSI CVS (based on Linux
      2.6.11) to Linux 2.6.12 (and now Linux 2.6.14).  It can't be
      considered even "beta" quality until Roger has had time to look at it.
   2. The user space hasn't been fully upgraded to Lenny, some bits of
      it are still Etch.  Some of this is due to our old kernel, we'll
      need at least 2.6.18 for full Lenny compatibility, some of it is
      due to laziness.

> Also, my hardware has a network interface that has a driver only in the
> latest 2.6.26 kernel, so it probably means that I would have to
> recompile the kernel for that driver,
What's the NIC?
> or could I just install a XEN on the two nodes and run OpenSSI as guest(?)
>   
That should be do-able, though I haven't made a Xen domU version of the 
OpenSSI kernel for a while.  (domU is the Xen terminology for a guest).
> In which case I may also be able to live migrate one of the nodes to the
> other node for hardware maintenance. Or would the RAM pose a problem in
> that scenario? (i.e. the first guest will take up all the ram of the machine,
> so there willbe no ram space to migrate the second one in.)
>   
With Xen you can dynamically reduce the amount of memory available to a 
domU.  (Within limits of course!)
> In XEN , can I replicate the whole OS via drbd, ie have both nodes boot
> from the same filesystem?
>   
Uh, maybe.  You're making my head hurt.

> Since drbd is of version 7 in openssi does it not support
> primary/primary or is it a special version that does?
>   
No, drbd, on OpenSSI doesn't support primary/primary, it doesn't need it 
due to OpenSSI's CFS.

If you made a primary/primary drbd at the dom0 (Xen host) level, you 
could just tell OpenSSI that it was a shared disk.
> And what about the CFS? say if I put a drbd in XEN, and run OpenSSI
> from there, can I use OCFS2 or something or do I have to or better use
> CFS?
>   
CFS would be easier.  I have no experience on using OCFS2,  so you'd be 
pretty much on your own.
> And last a repeat of the first question, is lenny's openssi in its
> current version a good solution for high availablity?
>   

Like I say, if you're worried about hardware problems.