HA with this hardware

[skeates]

I just wanted to get a straight answer regarding setting up Proxmox with HA. I have two physical servers HP DL360's G6 & I'm about to get some storage which will give me an NFS storage location.

2x HP DL360 G6
1x NFS Storage
1x Network Switch

Will Proxmox HA work with these bits of hardware or do I need anything extra?

I know realistically I should be using at least three physical servers, but budget contraints at the moment limit me to what I have so I want to make the best of what I have available. The servers have redundant psu's, dual processors hardware raid cards and multiple drives so they are as redundant as possible.

The plan is over time to add an additional physical server & a second storage device for redundancy.

I plan to take out Proxmox Support with this, but before I plunge into this I want to make sure I am able to achieve what I need to with what I have.

 

[m.ardito]

you can use a quorum disk (on the nfs storage) to have 3 votes, so it could work. see http://pve.proxmox.com/wiki/Two-Node_High_Availability_Cluster
but you need also fencing devices, and a good setup.

Marco

 

[skeates]

Thanks for that.

So I would still need a third machine for the fencing and if that is the case if I had a three node system would I then need a 4th machine to fence again or the three nodes would handle this them selves?

 

[pixel]

third machine for quorum, not fencing. you can do fencing with idrac/ipmi etc, or with switch mangement. if you can afford it, networked power switches are the best way.

 

[spirit]

you can use a quorum disk (on the nfs storage) to have 3 votes, so it could work. see http://pve.proxmox.com/wiki/Two-Node_High_Availability_Cluster
but you need also fencing devices, and a good setup.

Marco

you can't do a quorum disk with nfs, you need a block device (iscsi).

 

[m.ardito]

yes, correct: I should have written "on the same device now offering nfs", like a NAS (QNAP, SYNOLOGY, etc) that tipically can do iscsi too.

Marco

 

[m.ardito]

Thanks for that.

So I would still need a third machine for the fencing and if that is the case if I had a three node system would I then need a 4th machine to fence again or the three nodes would handle this them selves?

no, it is just 2node setup that need a third to have quorum if 1 node fails.
more than half of the hosts must be online and communicating in order to provide service so, your quorum must be > (more than) expected votes

each node (or quorum disk) tipically counts 1, so quorum is (nodes/2). if exp.votes > (nodes/2) you have quorum.

with 2 nodes, if one node fails, you have 1 vote but need quorum of 1. you have no quorum.
with 3 nodes, if one node fails, you have 2 votes and needed quorum is 1.5. you have quorum.
with 3 nodes, if two nodes fail, you have 1 vote and needed quorum is 1.5. you have no quorum.
with 4 nodes, if one node fails, you have 3 votes and needed quorum is 2. you have quorum.
with 4 nodes, if two nodes fail, you have 2 votes and needed quorum is 2. you have no quorum.
etc.

you can temporarily regain quorum to solve those cases but manually, not suited for HA. see pvecm command on the wiki pages.

Marco

 

[pixel]

skeats, yes, you can have HA but there will be points of failure. the NFS/qdisk server (unless thats already an HA setup), and the network switch are two of them. switches rarely fail. if either of those fail, data corruption is unlikely, since the data is now unavailable. there might be other failure points, so look carefully.

you have two options for fencing, ilo2 (the hp version of ipmi) and the switch. if the switch can be managed with a fencing device, thats probably simpler, at least in cabling. if you want to use ilo2, and you dont already have them set up for remote management, you could just use a pair of cross cables. this way, you can use either node to get to the others console.