vSphere Replication – Consider These Points Before Using It

vSphere Replication has been embedded in the ESXi kernel for quite sometime now.  When a virtual machine performs a storage ‘write’ this is mirrored by the vSCSI filter at the ESXi Host level before it is committed to disk.  The vSCSI filter sends its mirrored ‘write’ to the vSphere Replication Appliance which is responsible for transmitting the ‘writes’ to it’s target. normally in a DR site.

The process is shown at a high level in the diagram below.

vSphere Replication v0.1

I’m often asked by customer if they shoud consider using it given the benefits which it provides, which include:

  • Simplified management using hypervisor based replication
  • Multi-point in time retention policies to store more than one instance of a protected virtual desktop
  • Application consistency using Microsoft Windows Operation System with VMware Tools installed
  • VM’s can be replicated from and to any storage
  • An initial seed can be performed

As a impartial adviser, I have to provide the areas in which vSphere Replication isn’t as strong.  These are the points, I suggested are considered as part of any design:

  • vSphere Replication relies on the vRA, if this is offline or unavailable then replication stops for all virtual machines.
  • vSphere Replication requires the virtual machine to be powered on for replication to occour
  • vSphere Replication is not usually as efficient as array based replication which often have compression and intelligence built into the replication process.  If you have limited bandwidth you may violate restore point objectives
  • vSphere Replication will reduce the bandwidth available to other services/functions if you are using logically separated networks over 10GbE
    • Note that Network IO Control can be used to prioritise access to bandwidth in times of contention, but required Enterprise Plus licenses
  • vSphere Replication requires manual routing to send traffic across a replication VLAN which increases the complexity of the environment
  • vSphere Replication is limited to 200 virtual machines per Replication Appliance and 2000 virtual machines overall as detailed in VMware KB2102453
  • After an unplanned failover and reprotect, vSphere Replication uses an algorithm to perform a checksum, this can result in a full sync depending on length of separation and amount of data being changed.
  • vSphere Replication only provides replication for powered on virtual machines
  • In a HA event on an ESXi Host at the Production site will trigger a full synchronisation of the virtual machines that resided on the failed host. See vSphere Replication FAQ’s

The last point which for me is a deal breaker.  Let’s consider that last point again, if we have an ESXi Host that has a PSOD then all of the VM’s will require a full synchronisation.

What’s The Impact?

If we have an inter-site link of 100Mbps which has an overhead of 10%, this gives us an effect throughput of 90Mbps.

We have an average sized VMware environment with a couple of VM’s which hold 2TB of data each which are being replicated across a 100Mbps inter-site link then you are looking at over 4 days to perform a full synchronisation.

We also need to consider the impact on the rest of your VM’s who will have their restore point objective violated as the bandwidth is being consumed by the 2 x 2TB VM’s.  Not exactly where you want to be!

The Maths Per 2TB VM

8Mb equals 1MB

2TB equals = 16,777,216 Mbps

16,777,216 Mbps / 90 Mbps = 186,414 Seconds

186,414 seconds / 60 seconds = 3,107 Minutes

3,107 minutes / 60 hours = 51 Hours 47 Minutes

VMworld – A First Timers View

This is a guest blog post by one of my work colleagues Craig Bramley covering his first time experience at VMworld 2015.  Hope you enjoy it!

VMworld 2015

I was a newbie when it came to the VMworld events, and after hearing all the positive feedback from colleagues who have attended these events in the past, I was intrigued to say the least.

So, when I was approached to provide a blog post on my personal experiences at the 2015 European VMworld event held in Barcelona, as you can imagine, I jumped at the chance.

Hopefully, the following paragraphs will give you an insight into VMworld events if you haven’t attending them before, as well as provide a few helpful pointers.

Transportation

For attendees flying into Barcelona, there is a shuttle service to the venue. This is extremely handy. A good tip is to look out for the VMworld signs which are held by VMworld staff. They are not easy to spot, and they can be some distance from the arrivals exit, so don’t despair if you don’t immediately see them, keep walking and looking. Bear in mind that no shuttle service is offered from the Hotels, so make sure that Taxi fares are accounted for. If you are OK on the Metro, then you can collect a free Metro pass from the information desk at the venue which gives you 10 trips – I found this extremely useful because the queues for the Taxis can be absolutely gigantic.

VMworld Barcelona!

I knew VMworld was large, I mean, I heard the crazy stories, but I was not prepared for the sheer magnitude of the event. It is vast! The VMworld venue is Fira Barcelona Gran Via, which is a conference centre located just outside Barcelona City. To give you an idea of the size we are talking about here, the hands on labs alone takes up 45,000 Square feet and that is tiny in comparison to the other areas – like I said, vast! So, expect to walk around 10,000 to 16,000 steps a day at the event – (according to my colleagues Fitbit). That being said, Keep hydrated with water, this is provided free all day long, along with Coffee, Tea, various snacks and fruit from the many stations dotted around, and of-course don’t forget those comfortable shoes – you will thank me later.

Inside the venue with Craig Kilborn and I
Inside the venue with Craig Kilborn and I

VMworld staff are a plenty, you’ll see them in their recognisable VMworld T-Shirts, so don’t panic if you get lost or confused, you can either ask one of them for assistance, or use the many maps and information boards – I did ask (against my male instinct) as the maps can be confusing.

Map and information board showing session times
Map and information board showing session times

Once you are inside the venue, there are various halls, breakout areas, your mind will be literally boggled by all the big screens and bright lights. Luckily I had veteran VMworlders with me, but if you haven’t, I imagine that it can be a little overwhelming. Again, just ask if you aren’t sure.

Fellow VMworlder Craig Kilborn, beating me at pool, 3 times.
Fellow VMworlder Craig Kilborn, beating me at pool, 3 times.
One of the outdoor hang areas
One of the outdoor hang areas
The Indoor hang space with pool tables and table tennis tables
The Indoor hang space with pool tables and table tennis tables

Food

The food was amazing, I can’t comment on previous years but everyone I spoke to agreed that the food was great, and much improved on past events. There are large food halls, and food stalls located around the venue, serving many different types of food which I imagine caters for everyone, which is a good thing when attendees are attending from 88 different countries. There are seating areas, but if you can’t locate a table or chair (expected when there are +25000 attendees), just ask to sit at an occupied table, if there is space, people are welcoming and it won’t be a problem. If there isn’t space, don’t worry too much, as you tend to find people are happy to hang around and relax in the hallways, networking with fellow attendees while grabbing a bite to eat. In fact, I met quite a few new people while standing around eating.

Communication

I made a huge mistake. That mistake was to assume that my mobile phone would work in Spain. I have the correct plan at the end of the day, it says it will work, so it should right? Wrong! I didn’t realise that I had to call my provider prior to travelling for them to unlock my international outgoing calls, which requires a provider code to do so. So now, I am in Barcelona and in order to make calls I need to make a call?? I can’t even call the provider, as my phone can’t make calls! Strange process, but something to be aware of. It is always the little things that we overlook at the end of the day.

At the venue, there is Wi-Fi throughout, but bear in mind you are one of +25,000 attendees, all trying to log on and browse. This can only lead to one thing, intermittent performance. So if internet access is absolutely critical on your visit, bear this in mind too.

Solutions Exchange

The solutions exchange is the vendor area. This is a huge hall, crammed wall to wall with bright, shiny objects and vendor representatives who are eager to explain why their solution is better than the competitions. So eager in fact, that they entice you on to their stands with weird and wonderful freebies, anything from USB drives, to flashing bouncing balls, remote control helicopters, prize draws and logo embezzled T-Shirts are on offer in return for your time.

This is a very busy area and all joking aside, it is extremely beneficial, as we do not always get the chance to meet up with vendors back in the real world if they are not on our preferred partner lists. This gave me the chance to demo products, and get to know what other optional solutions are available to us. Some amazing solutions were on show, I really enjoyed this area (and some of the freebies).

The Solutions Exchange Main Entrance
The Solutions Exchange Main Entrance

Vendor Parties

Vendor parties are held every evening, with free food and drink at various local restaurants, bars and nightclubs. The choice is endless, and these parties are a very easy way to network with colleagues, and meet other IT industry representatives. However, be aware that late nights, involving free alcohol and lots of dad dancing can be fun – until you have to wake up early the next day! So, take it easy, it will be a long week if you feel terrible.

The VMworld party was headlined by Faithless, to give you an idea of the quality and scale of some of these parties.

Veeam Party with Craig Kilborn, a very green event!
Veeam Party with Craig Kilborn, a very green event!

Overall

Overall, I enjoyed my VMworld experience. Some advice I would give to anyone that is attending in 2016, along with all the advice throughout this post, is to download the VMworld App and register for sessions in advance.

The sessions get full, and if you haven’t registered, you have to queue, keeping your fingers crossed that the door staff can find space for you. I saw a lot of people being turned away, and if you came from overseas to see a particular session, it’s a long way to come to risk being disappointed.

I attended various sessions which covered areas around workforce mobility and EUC, VSAN, Hybrid Cloud, Horizon View, Horizon AIR and vRealize Automation which are all areas of particular interest to me. That being said, I can’t stress how important the social side of VMworld is, so don’t register for too many sessions and never get time to meet anyone / talk to vendors.

The general sessions take place every morning and cover various topics but there was a lot of aspect on application mobility, end user mobility, containerisation, SDDC and Hybrid Cloud.

As well as the usual technology topics, this year’s key notes was dominated by the Dell / EMC Merger, a merger that had been confirmed days before I attended the event. Michael Dell made an appearance – which is a big deal!

Well done VMworld on a great event.

VMworld 2015 Announcements – In a Nutshell

vmworld2015-logo-blackThe excitement of VMworld 2015 is upon us, and below are the key announcements.

Naturally, we will need to dig a bit deeper to understand the technology in more detail along with the limitations and costs.

  • VSAN 6.1
    • 2 x Node Cluster Supported
    • vSphere Metro Storage Cluster Supported
    • Windows Server Failover Clustering Supported
    • vROPs Integration (not sure if a management pack is needed)
    • vSphere Replication Enhanced 5 Min RPO

This answers a lot of use cases for me, especially the 2 x Node Cluster and vMSC support.

  • VMware Hybrid Cloud
    • Support for Layer 2 Networking Extension
    • Encryption over the WAN and optimisation
    • Cross Cloud vMotion (on-premises to vCloud Air)

Layer 2 is key here as a lot of customers have apps that break if you change subnets.  Zero downtime is pretty decent as well, however you still need to design for user access to applications and services in vCloud Air.

  • SRM 6.1
    • Metro Stretch Clusters, ability to live migrate across vCenters.  Think vMSC but with control for test and planned failover.

Another key enhancement here, lots of campus type customers such as Universities and NHS Trusts will look into this more deeply..

  • VAIO (vSphere API’s for IO Filtering)
    • Enables third party data services to intercept IO and optimise before hitting storage.
    • Initial use cases are caching and replication
    • Works with VMFS, Virtual Volumes and VSAN

Although VAIO was announced at VMworld 2014.  We should start to see some practical use-cases.  My best guess is that we will see in-memory optimisation for IO, same as Atlantis but without the need for a separate appliance.

VMworld Attendees – 86% Off VCP Course

VMware have pulled another one out of the hat when it comes to certification, they are offering 86% off the On Demand VCP course.

How Does It Work?

  1. Go see Julie in VMware Education & Certification lounge with your credit/debit card details.
  2. Pay $499 which is about £310
  3. Start the VMware vSphere: Install, Configure & Manage online course before the end of year.

The kicker is with this course, you have 90 days to complete it, which means you can do it at your own pace without committing the usual five days (annual leave or convincing your employers to fund the time).

Enjoy!