JP Vossen on 8 Aug 2018 18:23:58 -0700


[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]

Re: [PLUG] Virtualization clusters & shared storage

Firth, thanks to Lee and Andy for the term I didn't know for what I mean: hyper-converged infrastructure. 
	https://en.wikipedia.org/wiki/Hyper-converged_infrastructure

It looks like Proxmox does that:
	https://pve.proxmox.com/wiki/Hyper-converged_Infrastructure

Thanks Keith, I had seen LizardFS but was not aware of the implications.
Doug, Kubernetes is not in play, though it might be in the future. Or I may be missing your point. 

Lee, thanks for the insights and VMware updates, as always. :-)
I've used FreeNAS in the past and like it, but I'm not sure I'm explaining my thoughts as well as I'd like. But let me try this:
(I wrote this next part before I learned that "hyper-converged" is what I mean, but I'm leaving it here in case it's still useful.)
Assume for simplicity that I have 5 R710s with 24M RAM, 8 CPUs and 6x 2TB drives in RAID5 for 10TB local storage each. 

3 node cluster with redundant FreeNAS:
	1. VM node1: CPU/RAM used for VMs, 10TB local space wasted
	2. VM node2: CPU/RAM used, 10TB local space wasted
	3. VM node3: CPU/RAM used, 10TB local space wasted
	4. FreeNAS 1: CPU/RAM somewhat wasted, 10TB space available
5. FreeNAS 2: CPU/RAM somewhat wasted, 0TB space available since it's a mirror 

3 node cluster with -on-node-shared-storage- hyper-converged storage:
	1. VM node1: CPU/RAM used, 20TB local/shared space available +
	2. VM node2: CPU/RAM used, 20TB local/shared space available +
	3. VM node3: CPU/RAM used, 20TB local/shared space available +
+ For 20TB I'm assuming (3-1) * 10TB, for some kind of parity space loss. If it was REALLY smart, it would keep the store for the local VMs local while still replicating, but that would require a lot more hooks into the entire system, not just some kind of replicated system.
But the point here is that with my idea I have 2x the disk with 3/5ths the servers. Or put another way, I can now do a 5 node cluster with even more CPU, RAM and space dedicated to actually running VMs, and not lose 2/5ths of the nodes to just storing the VMs.
That said, I'd thought about the rebuild overhead, but not in depth, and that--and general "parity" or redundancy however implemented--are significant. So my 2/5ths comparisons are not 100% fair. But still, the idea apparently does have merit. 


On 08/08/2018 07:50 PM, Lee H. Marzke wrote:


JP, if you want cheap storage for your lab , I think you can't beat FreeNAS or
equiv rackmount solutions from https://www.ixsystems.com. I run my lab on
FreeNAS and a Dell 2950 server with 6x2TB disks and 2 x SSD. If you put storage
into the servers you will find all sorts of edge cases that you hadn't planned on.

Just taking down a server for quick RAM swap, will cause it to need to rebuild
using lots of network/CPU.   If you have TB of fast SSD storage on multiple servers and
don't have 10GB connectivity between hosts, or you have slow HD's you will have pain.
Generally you try to migrate data off nodes prior to maintenance - which may take several days.

The VMware solutions have changed a lot, and though it does not meet JP's
needs for *free*,  they may fit someone else's needs for a reliable / highly
available solution.    Of course ESXi and VSAN are free for 60 day trial after
install for lab use.

First there is a VMware Migrate *both* mode where you can migrate both the Hypervisor and
then storage in one go, where the two storage units are not connected across Hypervisors.
Needless to say this takes a long time to sequentially move memory , then disk to the remote
server, and it doesn't help improve HA.

Next VMware VSAN is caching on really fast and VMware is hiring like mad
to fill new VSAN technical sales roles Nationwide.   VSAN uses storage in each
host ( minimum of one SSD and one HD ) and uses high-performance object
storage on each compute node.  All VM objects are stored on two hosts
minimum, with vSAN taking care of all the distribution.  The hosts must be
linked on a 1GB ( pref 10GB ) private network for back-end communication.
Writes are sent and committed to two nodes before being acknowledged.
You get one big storage pool - and allocate storage to VM's as you like -
with no sub LUNs or anything else to manage.   If you have 4 or more hosts
instead of mirroring data over 2 hosts,  you can do erasure coding ( equiv
of RAID 5/6 but with disks spread out across hosts.   So now your not
losing 50% of your storage , but have more intensive CPU and network
operations.   The vSAN software is pre-installed into ESX these days - just
need to activate it and apply a license after the 60 free day trial.

Not sure why you say FreeNAS is wasting CPU in more nodes,  as those CPU cycles
would be used locally in the Hyperconverged solutions as well ( perhaps taking 10%
to 20% cycles away from a host for storage and replication ) so you may need more / larger
hosts in a hyperconverged solution to make up for that.   Remember mirroring
takes little CPU, but waste's 50% of your storage,  any erasure coding is
much more CPU intensive, and more network intensive.

The other solutions mentioned except a ZFS server are likely way too complex
for a lab storage solution.   Is a company really going to give
a lab team 6 months of effort to put together storage that may or may
not perform ?  Can you do a business justification to spend dozens of MM of
effort just to save the $20K on an entry level  TrueNAS ZFS ?

Lee


----- Original Message -----

From: "Vossen JP" <jp@jpsdomain.org>
To: "Philadelphia Linux User's Group Discussion List" <plug@lists.phillylinux.org>
Sent: Wednesday, 8 August, 2018 17:13:17
Subject: [PLUG] Virtualization clusters & shared storage



I have a question about virtualization cluster solutions.  One thing
that has always bugged me is that VM vMotion/LiveMigration features
require shared storage, which makes sense, but they always seem to
assume that shared storage is external, as in a NAS or SAN.  What would
be REALLY cool is a system that uses the cluster members "local" storage
as JBOD that becomes the shared storage.  Maybe that's how some of
solutions work (via Ceph, GlusterFS or ZFS?) and I've missed it, but
that seems to me to be a great solution for the lab & SOHO market.

What I mean is, say I have at least 2 nodes in a cluster, though 3+
would be better.  Each node would have at least 2 partitions, one for
the OS/Hypervisor/whatever and the other for shared & replicated
storage.  The "shared & replicated" partition would be, well, shared &
replicated across the cluster, providing shared storage without needing
an external NAS/SAN.

This is important to me because we have a lot of hardware sitting around
that has a lot of local storage.  It's basically all R710/720/730 with
PERC RAID and 6x or 8x drive bays full of 1TB to 4TB drives.  While I
*can* allocate some nodes for FreeNAS or something, that increases my
required node count and wastes the CPU & RAM in the NAS nodes while also
wasting a ton of local storage on the host nodes.  It would be more
resource efficient to just use the "local" storage that's already
spinning.  The alternative we're using now (that sucks) is that the
hypervisors are all just stand-alone with local storage.  I'd rather get
all the cluster advantages without the NAS/SAN issues
(connectivity/speed, resilience, yet more rack space & boxes).

Are there solutions that work that way and I've just missed it?


Related, I'm aware of these virtualization environment tools, any more
good ones?
1. OpenStack, but this is way too complicated and overkill
2. Proxmox sounds very cool
3. Cloudstack likewise, except it's Java! :-(
4. Ganeti was interesting but it looks like it may have stalled out
around 2016
5. https://en.wikipedia.org/wiki/OVirt except it's Java and too limited
6. https://en.wikipedia.org/wiki/OpenNebula with some Java and might do
on-node-shared-storage?
7. Like AWS: https://en.wikipedia.org/wiki/Eucalyptus_(software) except
it's Java

I'm asking partly for myself to replace my free but not F/OSS ESXi
server at home and partly for a work lab that my team needs to rebuild
in the next few months.  We have a mishmash right now, much of it ESXi.
We have a lot of hardware laying around, but we have *no budget* for
licenses for anything.  I know Lee will talk about the VMware starter
packs and deals like that but we not only have no budget, that kind of
thing is a nightmare politically and procedurally and is a no-go; it's
free or nothing.  And yes I know that free costs money in terms of
people time, but that's already paid for and while we're already busy,
this is something that has to happen.

Also we might like to branch out from ESXi anyway...  We are doing a
some work in AWS, but that's not a solution here, though cross cloud
tools like Terraform (and Ansible) are in use and the more we can use
them here too the better.

Thanks,
JP
--  -------------------------------------------------------------------
JP Vossen, CISSP | http://www.jpsdomain.org/ | http://bashcookbook.com/
___________________________________________________________________________
Philadelphia Linux Users Group         --        http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug