Tag Archives: virtualization

How to successfully Virtualize MS Exchange – Part 8 – Local Storage

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As discussed in Part 7, Local Storage is probably the most basic form of storage we can present to ESXi and use for Exchange MBX/MSR VMs.

The below screen shot shows what local storage can look like to an ESXi host.

LocalStorage

As we can see above, the highlighted datastore is simply an SSD formatted with VMFS5. So in this case a single drive not running RAID, and therefore in the event of the drive failing, any data on the drive would be permanently lost.

Note: The above image is simply an example. In reality multiple drives most likely SAS or SATA would be used as SSD is unnecessary for Exchange.

In some ways this is very similar to a physical Exchange deployment on JBOD storage and I would like to echo the recommendations Microsoft give for JBOD deployments from the Exchange 2013 storage configuration options guide and say for JBOD deployments, I strongly recommend at least 3 database copies.

As per the recommendation in Part 4 (DRS), MS Exchange MBX/MSR VMs should always run on separate ESXi hosts to ensure a single host failure does not potentially cause an issue for the DAG. This is especially important because if two Exchange servers shared the same ESXi host and local storage, a single ESXi host outage could cause data loss and downtime for part or all of the Exchange environment.

The below is a screen shot from the Exchange 2013 storage configuration options guide showing the recommendations based on RAID or JBOD deployments. In my option these recommendations also apply to virtualized Exchange deployments on Local storage.

JBODexchange

Another option is to use Local Storage in a RAID configuration to eliminate the Single Point of Failure (SPOF) of a single drive failure.

Again, I agree with Microsoft’s recommendations and suggest at least two database copies when using a RAID configuration and again, each Exchange VM must run on its own ESXi host on dedicated physical disks.

Note: The RAID controller itself is still a SPOF which is why multiple copies is recommended from both an availability and data protection perspective.

Let’s now discuss the pros and cons for using Local Storage with JBOD for your Virtualized Exchange Deployment.

PROS

1. Generally lower cost per GB than centralized storage (e.g.: SAN)
2. Higher usable capacity per drive compared to RAID or centralized storage configurations using RAID or other propitiatory data protection techniques.
3. Local JBOD Storage formatted with VMFS is a fully supported configuration

CONS

1. No protection from data loss in the event of a JBOD drive failure. Note: For non DAG deployments, RAID and 3rd party backups should always be used!
2. Performance/Capacity in JBOD deployments is limited to the capabilities of a single drive.
3. Loss of Virtualization functionality such as HA / DRS and vMotion (without performing a Storage vMotion every time)
4. Can be difficult/costly to scale when nearing capacity.
5. Increased Management (Operational) overheads managing decentralized storage
6. At least 3 database copies are recommended, requiring more Exchange MBX/MSR servers.
7. Little/no protection against data corruption which may lead to all DAG copies suffering corruption. Note: If the corruption is not discovered in time, LAGGED copies can also be compromised.
8. Capacity cannot be shared between between ESXi hosts which may lead to inefficient use of the available capacity.

Next here are some pros and cons for using Local Storage with RAID for your Virtualized Exchange Deployment.

PROS

1. Generally lower cost per GB than centralized storage (e.g.: SAN)
2. A single drive failure will not cause data loss or a DAG failover
3. Performance is not limited to a single drives capabilities
4.Local Storage with RAID formatted with VMFS is a fully supported configuration
5. As there is no data loss with a single drive failure, less database copies are required (2 instead of >=3 for JBOD)

CONS

1. Increased Management (Operational) overheads managing decentralized storage
2. Performance/Capacity is limited to the capabilities of a single drive
3. Loss of Virtualization functionality such as HA / DRS and vMotion (without performing a Storage vMotion every time)
4. Little/no protection against data corruption which may lead to all DAG copies suffering corruption. Note: If the corruption is not discovered in time, LAGGED copies can also be compromised.
5. Capacity cannot be shared between ESXi hosts which may lead to inefficient use of the available capacity
6. Performance is constrained by a single RAID controller / set of drives and can be difficult/costly to scale when nearing capacity.

For more information about data corruption for JBOD or RAID deployments, see “Data Corruption“.

Recommendations:

1. When using local storage, (JBOD or RAID), as per Part 4, run only one Exchange MBX/MSR VM per ESXi host
2. Use dedicated physical disks for Exchange MBX/MSR VM (i.e.: Do not share the same disks with other workloads)
3. Store the Windows OS / Exchange application VMDK on local storage which is configured with RAID to ensure a single drive does not cause the VM an outage.
4. Ensure ESXi itself is install on local storage configured with RAID (and not a USB key) as the Exchange VM is dependant on that host and is not protected by vSphere HA. Nor is it easily/quickly portable due to the storage not being shared.

Summary:

Using Local Storage in either a JBOD or RAID configuration is fully supported by Microsoft and is a valid option for MS Exchange deployments.

In my opinion Local Storage deployments have more downsides than upsides and I would recommend considering other storage options for Virtualized Exchange deployments.

Other options along with my recommended options will be discussed in the next 3 parts of this series.

Back to the Index of How to successfully Virtualize MS Exchange.

~ Post Updated January 2nd 2015 Thanks to feedback from @zerszenyi ~

Enterprise Architecture & Avoiding tunnel vision.

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Recently I have read a number of articles and had several conversations with architects and engineers across various specialities in the industry and I’m finding there is a growing trend of SMEs (Subject Matter Experts) having tunnel vision when it comes to architecting solutions for their customers.

What I mean by “Tunnel Vision” is that the architect only looks at what is right in front of him/her (e.g.: The current task/project) , and does not consider the implications of how the decisions being made for this task may impact the wider I.T infrastructure and customer from a commercial / operational perspective.

In my previous role I saw this all to often, and it was frustrating to know the solutions being designed and delivered to the customers were in some cases quite well designed when considered in isolation, but when taking into account the “Big Picture” (or what I would describe as the customers overall requirements) the solutions were adding unnecessary complexity, adding risk and increasing costs, when new solutions should be doing the exact opposite.

Lets start with an example;

Customer “ACME” need an enterprise messaging solution and have chosen Microsoft Exchange 2013 and have a requirement that there be no single points of failure in the environment.

Customer engages an Exchange SME who looks at the requirements for Exchange, he then points to a vendor best practice or reference architecture document and says “We’ll deploy Exchange on physical hardware, with JBOD & no shared storage and use Exchange Database Availability Groups for HA.”

The SME then attempts to justify his recommendation with “because its Microsoft’s Best practice” which most people still seem to blindly accept, but this is a story for another post.

In fairness to the SME, in isolation the decision/recommendation meets the customers messaging requirements, so what’s the problem?

If the customers had no existing I.T and the messaging system was going to be the only I.T infrastructure and they had no plans to run any other workloads, I would say the solution proposed could be a excellent solution, but how many customers only run messaging? In my experience, none.

So lets consider the customer has an existing Virtual environment, running Test/Dev, Production and Business Critical applications and adheres to a “Virtual First” policy.

The customer has already invested in virtualization & some form of shared storage (SAN/NAS/Web Scale) and has operational procedures and expertises in supporting and maintaining this environment.

If we were to add a new “silo” of physical servers, there are many disadvantages to the customer including but not limited too;

1. Additional operational documentation for new Physical environment.

2. New Backup & Disaster Recovery strategy / documentation.

3. Additional complexity managing / supporting a new Silo of infrastructure.

4. Reduced flexibility / scalability with physical servers vs virtual machines.

5. Increased downtime and/or impact in the event hardware failures.

6. Increased CAPEX due to having to size for future requirements due to scaling challenges with physical servers.

So what am I getting at?

The cost of deploying the MS Exchange solution on physical hardware could potentially be cheaper (CAPEX) Day 1 than virtualizing the new workload on the existing infrastructure (which likely needs to be scaled e.g.: Disk Shelves / Nodes) BUT would likely result overall higher TCO (Total Cost of Ownership) due to increased complexity & operational costs due to the creation of a new silo of resources.

Both a physical or virtual solution would likely meet/exceed the customers basic requirement to serve MS Exchange, but may have vastly different results in terms of the big picture.

Another example would be a customer has a legacy SAN which needs to be replaced and is causing issues for a large portion of the customers workloads, but the project being proposed is only to address the new Enterprise messaging requirements. In my opinion a good architect should consider the big picture and try to identify where projects can be combined (or a projects scope increased) to ensure a more cost effective yet better overall result for the customer.

If the architect only looked at Exchange and went Physical Servers w/ JBOD, there is zero chance of improvement for the rest of the infrastructure and the physical equipment for Exchange would likely be oversized and underutilized.

It will in many cases be much more economical to combine two or more projects, to enable the purchase of a new technology or infrastructure components and consolidate the workloads onto shared infrastructure rather than building two or more silo’s which add complexity to the environment, and will likely result in underutilized infrastructure and a solution which is inferior to what could have been achieved by combining the projects.

In conclusion, I hope that after reading this article, the next time you or your customers embark on a new project, that you as the Architect, Project Manager, or Engineer consider the big picture and not just the new requirement and ensure your customer/s get the best technical and business outcomes and avoid where possible the use of silos.