Re: [Xen-users] Linux Fiber or iSCSI SAN

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 06/11/2013 06:28 PM, Errol Neal wrote:
> On Tue, 06/11/2013 01:23 PM, Nick Khamis <symack@xxxxxxxxx> wrote:
> > > > ESOS by all means is not perfect. I'm running an older release because it's 
> > > > impossible to
> > > > upgrade a production system without downtime using ESOS (currently) but I was
> > > > impressed with it non the less and i can see where it's going.
> > Thanks again Errol. Just our of curiosity was any of this replicated?
> That is my next step. I had been planning of using Ininiband,
> SDP and DRBD, but there are some funky issues there. I just
> never got around to it.
The first thing that jumps out at me here is infiniband. Do you have the 
infrastructure and cabling in place to actually do that? This can be 
very relevant depending on your environment. If you are planning to get 
some cheap kit on eBay to do this, that's all well and good, but will 
you be able to get a replacement if something breaks in a year or three? 
One nice thing about ethernet is that it will always be around, it will 
always be cheap, and it will always be compatible.
For most uses multiple gigabit links bonded together are ample. Remember 
that you will get, on a good day, about 120 IOPS per disk. Assuming a 
typical 4K operation size that's 480KB/s/disk. At 16KB/op that is still 
1920KB/s/disk. At that rate you'd need 50 disks to saturate a single 
gigabit channel. And you can bond a bunch of them together for next to 
nothing in switch/NIC costs.
> I think what's necessary over replication is a dual head
> configuration.
Elaborate?

> A combination of RAID1, CLVM, Pacemaker, SCST and shared storage
> between two nodes should suffice.
In what configuration?

Gordan

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