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My ramblings on the stuff that holds it all together
Now that VMware are moving away from ESX classic (with service console) to the ESXi model I have experienced a couple of issues recently that got me wondering if NFS will be a more appropriate model for VM storage going forward. in recent versions of ESX (3.5 and 4) NFS has moved away from just being recommended for .ISO/template storage and has some big names behind it for production VM storage.
I’m far from a storage expert, but I know enough to be dangerous… feel free to comment if you see it differently.
“out of band” Access speed
Because VMFS is a proprietary block-storage file system you are only able to access it via an ESX host you can’t easily go direct (VCB…maybe, but it’s not easy), in the past this hasn’t been too much of an issue; however whilst building a new ESXi lab environment on standard hardware I found excessive transfer times using the Datastore browser in the VI Client, 45mins+ to copy a 1.8GB .ISO file to a VMFS datastore, or import virtual machines and appliances; even using Veeam FastSCP didn’t make a significant difference.
I spent ages checking out network/duplex issues but in desperation I tried it against ESX classic (based on this blog post I found) installed on the same host and that transfer time was less than 1/2 (22mins) – which still wasn’t brilliant – but I cranked out Veeam FastSCP and did it in 6mins!
So, lesson learnt? relying on the VI client/native interfaces to transfer large .ISO files or VMs into datastores slow and you have to go via the Hypervisor layer, which oddly doesn’t seem optimized for this sort of access. Veeam FastSCP fixes most of this – but only on ESX classic as it has some service-console cleverness that just isn’t possible on ESXi.
With ESX classic going away in favour of ESXi, there will need to be an alternative for out of band access to datastores – either direct access or an improved network stack for datastore browsing
This is important where you manage standalone ESX hosts (SME), or want to perform a lot of P2V operations as all of those transfers use this method.
In the case of using NFS, given appropriate permissions you can go direct to the volume holding the VMs using a standard network protocol which is entirely outside of the ESX/vCenter. upload/download transfers thus are at at the speed of the data mover or server hosting the NFS mount point so are not constrained by ESX.
To me, Fibre Channel was always more desirable for VM storage as it offered lossless bandwidth up to 4Gb/s (now 8Gb/s) but Ethernet (which is obviously required to serve NFS) now has 10Gb/s bandwidth and loss-less technology like FCoE, some materials put NFS about 10% slower than VMFS – considering the vast cost difference between dedicated FC hardware and commodity Ethernet/NAS storage I think that’s a pretty marginal difference when you factor in the simplicity of managing NFS vs. FC (VLANs, IPs vs. Zoning, Masking etc.).
FCoE maybe addresses the balance and provides the best solution to performance and complexity but doesn’t really address the out of band access issue I’ve mentioned here as it’s a block-storage protocol.
If you have a problem with your vCenter/ESX installation you are essentially locked out of access to the virtual machines, it’s not easy to just mount up the VMFS volume on a host with a different operating system and pull out/recover the raw virtual machines.
With NFS you have more options in this situation, particularly in small environments.
Storage Host Based Replication
For smaller environments SAN-SAN replication is expensive, and using NFS presents some interesting options for data replication across multiple storage hosts using software solutions.
I’d love to hear your thoughts..
I am currently presenting a follow-up to my previous vTARDIS session for the London VMware Users Group where I demonstrated a 2-node ESX cluster on cheap PC-grade hardware (ML-115g5).
The goal of this build is to create a system you can use for VCP and VCDX type study without spending thousands on normal production type hardware (see the slides at the end of this page for more info on why this is useful..) – Techhead and I have a series of joint postings in the pipeline about how to configure the environment and the best hardware to use.
As a bit of a tangent I have been seeing how complex an environment I can get out of a single server (which I have dubbed v.T.A.R.D.I.S: Nano Edition) using virtualized ESXi hosts, the goals were;
The main stumbling block I ran into with the previous build was the performance of the SATA hard disks I was using, SCSI was out of my budget and SATA soon gets bogged down with concurrent requests which makes it slow; so I started to investigate solid state storage (previous posts here).
By keeping the virtual machine configurations light and using thin-provisioning I hoped to squeeze a lot of virtual machines into a single disk, previous findings seem to prove that cheap-er consumer grade SSD’s can support massive amount of IOps when compared to SATA (Eric Sloof has a similar post on this here)
So, I voted with my credit card and purchased one of these from Amazon – it wasn’t “cheap” at c.£200 but it will let me scale my environment bigger than I could previously manage which means less power, cost, CO2 and all the other usual arguments you try to convince yourself that a gadget is REQUIRED.
So the configuration I ended up with is as follows;
|1 x HP ML115G5, 8Gb RAM, 144Gb SATA HDD||c.£300 (see here) but with more RAM|
|1 x 128Gb Kingston 2.5” SSDNow V-Series SSD||c£205|
I installed ESX4U1 classic on the physical hardware then installed 8 x ESXi 4U1 instances as virtual machines inside that ESX installation
This diagram shows the physical server’s network configuration
In order for virtualized ESXi instances to talk to each other you need to update the security setting on the physical host’s vSwitch only as shown below;
This diagram shows the virtual network configuration within each virtualized ESXi VM with vSwitch and dvSwitch config side-side.
I then built a Windows 2008R2 Virtual Machine with vCenter 4 Update 1 as a virtual machine and added all the hosts to it to manage
I clustered all the virtual ESXi instances into a single DRS/HA cluster (turning off admission control as we will be heavily oversubscribing the resources of the cluster and this is just a lab/PoC setup
Cluster Summary – 8 x virtualized ESXi instances – note the heavy RAM oversubscription, this server only has 8Gb of physical RAM – the cluster thinks it has nearly 64Gb
I then built an OpenFiler Virtual Machine and hooked it up to the internal vSwitch so that the virtualized ESXi VMs can access it via iSCSI, it has a virtual disk installed on the SSD presenting a 30Gb VMFS volume over iSCSI to the virtual cluster nodes (and all the iSCSI traffic is essentially in-memory as there is no physical networking for it to traverse.
Each virtualized ESXi node then runs a number of nested virtual machines (VM’s running inside VMs)
In order to get Nested virtual machines to work; you need to enable this setting on each virtualized ESXi host (the nested VM’s themselves don’t need any special configuration)
Once this was done and all my ESXi nodes were running and settled down, I have a script to build out a whole bunch of nested virtual machines to execute on my 8-node cluster. the VM’s aren’t anything special – each has 512Mb allocated to it and won’t actually boot past the BIOS because my goal here is just to simulate a large number of virtual machines and their configuration within vCenter, rather than meet an actual workload – remember this is a single server configuration and you can’t override the laws of physics, there is only really 8Gb or RAM and 4 CPU cores available.
Each of the virtual machines was connected to a dvSwitch for VM traffic – which you can see here in action (the dvUplink is actually a virtual NIC on the ESXi host).
I power up the virtual machines in batches of 10 to avoid swamping the host, but the SSD is holding up very well against the I/O
With all 60 of the nested VMs and virtualized ESXi instances loaded these are the load stats
I left it to idle overnight and these are the performance charts for the physical host; the big spike @15:00 was the scripts running to deploy the 60 virtual machines
Physical memory consumption – still a way to go to get it to 8Gb – who says oversubscription has no use? 🙂
So, in conclusion – this shows that you can host a large number of virtual machines for a lab setup, this obviously isn’t of much use in a production environment because as soon as those 60VM’s actually start doing something they will consume real memory and CPU and you will run out of raw resources.
The key to making this usable is the solid state disk – in my previous experiments I found SATA disks just got soaked under load and caused things like access to the VMFS to fail (see this post for more details)
Whilst not a production solution, this sort of setup is ideal for VCP/VCDX study as it allows you to play with all the enterprise level features like dvSwitch and DRS/HA that really need more than just a couple of hosts and VMs to understand how they really work. for example; you can power-off one of the virtual ESXi nodes to simulate a host failure and invoke the HA response, similarly you can disconnect the virtual NIC from the ESXi VM to simulate the host isolation response.
Whilst this post has focused on non-production/lab scenarios it could be used to test VMware patch releases for production services if you are short on hardware and you can quite happily run Update manager in this solution.
If you run this lab at home it’s also very power-efficient and quiet, there are no external cables or switches other than a cross-over cable to a laptop to run the VI Client and administer it; you could comfortably have it in your house without it bothering anyone – and with an SSD there is no hard disk noise under load either 🙂
Thin-provisioning also makes good use of an SSD in this situation as this screenshot from a 30Gb virtual VMFS volume shows.
The only thing you won’t be able to play around with seriously in this environment is the new VMware FT feature – it is possible to enable it using the information in this post and learn how to enable/disable but it won’t remain stable and the secondary VM will loose sync with the primary after a while as it doesn’t seem to work very well as a nested VM. If you need to use FT for now you’ll need at least 2 physical FT servers (as shown in the original vTARDIS demo)
If you are wondering how noisy it it at power-up/down TechHead has this video on YouTube showing the scary sounding start-up noise but how quiet it gets once the fan control kicks-in.
Having completed my VCP4 and 3 I’m on the path to my VCDX and next up is the enterprise exam so this lab is going to be key to my study when the vSphere exams are released.
Following on from my recent blog posts about the various ways to configure ML115 G5 servers to run ESX, I thought I would do some further experimenting on some older hardware that I have.
I have a Dell D620 laptop with dual-core CPU and 4Gb of RAM which is now no longer my day-day machine, because of the success I had with SSD drives I installed a 64Gb SSD in this machine
I followed these instructions to install ESXi 4 Update 1 to a USB Lego brick flash drive (freebie from EMC a while ago and plays nicely to my Legogeekdom). I can then boot my laptop from this USB flash drive to run ESXi.
I am surprised to say it worked 1st time, booted fully and even supports the on-board NIC!
So, there you go – another low-cost ESXi server for your home lab that even comes with its own hot-swappable built-in battery UPS 🙂
The on-board SATA disk controller was also detected out of the box
A quick look on eBay and D620’s are going for about £250, handy!
Here is a screenshot of the laptop running a nested copy of ESXi, interestingly I also told the VM it had 8Gb of RAM, when it only has 4Gb of physical RAM.