Tag Archives: drs

Example Architectural Decision – VMware DRS automation level for a Nutanix environment

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Problem Statement

What is the most suitable DRS automation level and migration threshold for a vSphere cluster running on Nutanix?

Requirements

1. Ensure optimal performance for Business Critical Applications
2. Minimize complexity where possible

Assumptions

1. Workload types and size are unpredictable and workloads may vary greatly and without notice
2. The solution needs to be as automated as possible without introducing significant risk
3. vSphere 5.0 or later

Constraints

1. 2 x 10GB NICs per ESXi host (Nutanix node)

Motivation

1. Prevent unnecessary vMotion migrations which will impact host & cluster performance
2. Ensure the cluster standard deviation is minimal
3. Reduce administrative overhead of reviewing and approving DRS recommendations
4. Ensure optimal storage performance

Architectural Decision

Use DRS in Fully Automated mode with setting “3” – Apply priority 1,2 and 3 recommendations

Create a DRS “Should run on hosts in group” rule for each Business Critical Applications (BCAs) and configure each BCA to run on a single specified host (ensuring BCA’s are separated or grouped according to workload)

DRS Automation will be Disabled for all Controller VMs (CVMs)

Justification

1. Fully Automated DRS prevents excessive vMotion migrations that do not provide significant compute benefits to cluster balance as the vMotion itself will use cluster & network resources

2. Ensure the Nutanix Distributed File System , specifically the “Curator” component does not need to frequently relocate data between Nutanix nodes (ESXi hosts) direct attached storage to ensure virtual machine/s have local access to data. Doing so would put additional load on the Controller VM (and Curator service), local/remote storage and the network.

2. Ensure cluster remains in a reasonably load balanced state without resource being wasted on load balancing the compute layer to only achieve minimal improvement which may impact the storage/network layer/s.

3. Applying Level 1,2 and 3 recommendations means recommendations that must be followed to satisfy cluster constraints, such as affinity rules and host maintenance will be applied (Level 1) as well as applying recommendations with four or more stars (Level 2) that promise a significant improvement in the cluster’s load balance. In the event significant improvement to the clusters load balance will be achieved, movement of data at the storage layer (via the CVM / Network) can be justified

3. DRS is a low risk, proven technology which has been used in large production environments for many years

4. Setting DRS to manual would be a significant administrative (BAU) overhead and introduce additional risks such as human error and situations where contention may go unnoticed which may impact performance of one or more VMs

5. Setting a more aggressive DRS migration threshold may put an additional load on the cluster which will likely not result in significantly better cluster balance (or VM performance) and could result in significant additional workload for the ESXi hosts (compute layer), the Nutanix Controller VM (CVM) ,network & underlying storage.

6. By using DRS “Should run on this host” rules for Business Critical Applications (BCAs) will ensure consistent performance for these workloads (by keeping VMs on the same ESXi host/Nutanix node where its data is local) without introducing significant complexity or limiting vSphere functionally

Implications

1. In some circumstances the DRS cluster may have a low level of imbalance

2. DRS will not move workloads via vMotion where only a moderate improvement to the cluster will be achieved

3. At times, including after performing updates (via VUM) of ESXi hosts (Nutanix Nodes) the cluster may appear to be unevenly balanced as DRS may calculate minimal benefit from migrations. Setting DRS to “Use Fully automated and Migration threshold 3” for a short period of time following maintenance should result in a more evenly balanced DRS cluster with minimal (short term) increased workload for the Nutanix Controller VM (CVM) , network & underlying storage.

4. DRS rules will need to be created for Business Critical Applications

Alternatives

1.Use Fully automated and Migration threshold 1 – Apply priority 1 recommendations
2.Use Fully automated and Migration threshold 3 – Apply priority 1,2 recommendations
3. Use Fully automated and Migration threshold 4- Apply priority 1,2,3 and 4 recommendations
4.Use Fully automated and Migration threshold 5- Apply priority 1,2,3,4 & 5 recommendations
5. Set DRS to manual and have a VMware administrator assess and apply recommendations
6. Set DRS to “Partially automated”

Related Articles

1. Storage DRS and Nutanix – To use or not to use, That is the question

Example Architectural Decision – ESXi Host Hardware Sizing (Example 1)

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Problem Statement

What is the most suitable hardware specifications for this environments ESXi hosts?

Requirements

1. Support Virtual Machines of up to 16 vCPUs and 256GB RAM
2. Achieve up to 400% CPU overcommitment
3. Achieve up to 150% RAM overcommitment
4. Ensure cluster performance is both consistent & maximized
5. Support IP based storage (NFS & iSCSI)
6. The average VM size is 1vCPU / 4GB RAM
7. Cluster must support approx 1000 average size Virtual machines day 1
8. The solution should be scalable beyond 1000 VMs (Future-Proofing)
9. N+2 redundancy

Assumptions

1. vSphere 5.0 or later
2. vSphere Enterprise Plus licensing (to support Network I/O Control)
3. VMs range from Business Critical Application (BCAs) to non critical servers
4. Software licensing for applications being hosted in the environment are based on per vCPU OR per host where DRS “Must” rules can be used to isolate VMs to licensed ESXi hosts

Constraints

1. None

Motivation

1. Create a Scalable solution
2. Ensure high performance
3. Minimize HA overhead
4. Maximize flexibility

Architectural Decision

Use Two Socket Servers w/ >= 8 cores per socket with HT support (16 physical cores / 32 logical cores) , 256GB Ram , 2 x 10GB NICs

Justification

1. Two socket 8 core (or greater) CPUs with Hyper threading will provide flexibility for CPU scheduling of large numbers of diverse (vCPU sized) VMs to minimize CPU Ready (contention)

2. Using Two Socket servers of the proposed specification will support the required 1000 average sized VMs with 18 hosts with 11% reserved for HA to meet the required N+2 redundancy.

3. A cluster size of 18 hosts will deliver excellent cluster (DRS) efficiency / flexibility with minimal overhead for HA (Only 11%) thus ensuring cluster performance is both consistent & maximized.

4. The cluster can be expanded with up to 14 more hosts (to the 32 host cluster limit) in the event the average VM size is greater than anticipated or the customer experiences growth

5. Having 2 x 10GB connections should comfortably support the IP Storage / vMotion / FT and network data with minimal possibility of contention. In the event of contention Network I/O Control will be configured to minimize any impact (see Example VMware vNetworking Design w/ 2 x 10GB NICs)

6. RAM is one of the most common bottlenecks in a virtual environment, with 16 physical cores and 256GB RAM this equates to 16GB of RAM per physical core. For the average sized VM (1vCPU / 4GB RAM) this meets the CPU overcommitment target (up to 400%) with no RAM overcommitment to minimize the chance of RAM becoming the bottleneck

7. In the event of a host failure, the number of Virtual machines impacted will be up to 64 (based on the assumed average size VM) which is minimal when compared to a Four Socket ESXi host which would see 128 VMs impacted by a single host outage

8. If using Four socket ESXi hosts the cluster size would be approx 10 hosts and would require 20% of cluster resources would have to be reserved for HA to meet the N+2 redundancy requirement. This cluster size is less efficient from a DRS perspective and the HA overhead would equate to higher CapEx and as a result lower the ROI

9. The solution supports Virtual machines of up to 16 vCPUs and 256GB RAM although this size VM would be discouraged in favour of a scale out approach (where possible)

10. The cluster aligns with a virtualization friendly “Scale out” methodology

11. Using smaller hosts (either single socket, or less cores per socket) would not meet the requirement to support supports Virtual machines of up to 16 vCPUs and 256GB RAM , would likely require multiple clusters and require additional 10GB and 1GB cabling as compared to the Two Socket configuration

12. The two socket configuration allows the cluster to be scaled (expanded) at a very granular level (if required) to reduce CapEx expenditure and minimize waste/unused cluster capacity by adding larger hosts

13. Enabling features such as Distributed Power Management (DPM) are more attractive and lower risk for larger clusters and may result in lower environmental costs (ie: Power / Cooling)

Alternatives

1.  Use Four Socket Servers w/ >= 8 cores per socket , 512GB Ram , 4 x 10GB NICs
2.  Use Single Socket Servers w/ >= 8 cores , 128GB Ram , 2 x 10GB NICs
3. Use Two Socket Servers w/ >= 8 cores , 512GB Ram , 2 x 10GB NICs
4. Use Two Socket Servers w/ >= 8 cores , 384GB Ram , 2 x 10GB NICs
5. Have two clusters of 9 hosts with the recommended hardware specifications

Implications

1. Additional IP addresses for ESXi Management, vMotion, FT & Out of band management will be required as compared to a solution using larger hosts

2. Additional out of band management cabling will be required as compared to a solution using larger hosts

Related Articles

1. Example Architectural Decision – Network I/O Control for ESXi Host using IP Storage (4 x 10 GB NICs)

2. Example VMware vNetworking Design w/ 2 x 10GB NICs

3. Network I/O Control Shares/Limits for ESXi Host using IP Storage

4. VMware Clusters – Scale up for Scale out?

5. Jumbo Frames for IP Storage (Do not use Jumbo Frames)

6. Jumbo Frames for IP Storage (Use Jumbo Frames)

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Example Architectural Decision – BC/DR Solution for vCloud Director

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Problem Statement

What is the most suitable BC/DR solution for a vCloud director environment?

Requirements

1. Ensure the vCloud solution can tolerate a site failure in an automated manner
2. Ensure the vCloud solution meets/exceeds the RTO of 4hrs
3. Comply with all requirements of the Business Continuity Plan (BCP)
4. Solution must be a supported vSphere / vCloud Configuration
5. Ensure all features / functionality of the vCloud solution are available following a DR event

Assumptions

1. Datacenters are in an Active/Active configuration
2. Stretched Layer 2 network across both datacenters
3. Storage based replication between sites
4. vSphere 5.0 Enterprise Plus or later
5. VMware Site Recovery Manager 5.0 or later
6, vCloud Director 1.5 or later
7. There is no requirement for workloads proposed to be hosted in vCloud to be at one datacenter or another

Constraints

1. The hardware for the solution has already been chosen and purchased. 6 x 4 Way, 32 core Hosts w/ 512GB RAM and 4 x 10GB
2. The storage solution is already in place and does not support a Metro Storage Cluster (vMSC) configuration

Motivation

1. Meet/Exceed availability requirements
2. Minimize complexity

Architectural Decision

Use the vCloud DR solution as described in the “vCloud Director Infrastructure Resiliency Case Study” (By Duncan Epping @duncanyb and Chris Colotti @Ccolotti )

In Summary, Host the vSphere/vCloud Management virtual machines on an SRM protected cluster.

Use a dedicated cluster for vCloud compute resources.

Configure the vSphere cluster which is dedicated to providing compute resources to the vCloud environment (Provider virtual data center – PvDC) to have four (4) compute nodes  located at Datacenter A for production use and two (2) compute nodes located at Datacenter B (in ”Maintenance mode”) dedicated to DR.

Storage will not be stretched across sites; LUNs will be presented locally from “Datacenter A” shared storage to the “Datacenter A” based hosts. The “Datacenter A” storage will be replicated synchronously to “Datacenter B” and presented from “Datacenter B” shared storage to the two (2) “Datacenter B” based hosts. (No stretched Storage between sites)

In the event of a failure, SRM will recover the vSphere/vCloud Management virtual machines bringing back online the Cloud, then a script as the last part of the SRM recovery plan, Mounts the replicated storage to the ESXi hosts in “Datacenter B” and takes the two (2) hosts at “Datacenter B” out of maintenance mode. HA will then detect the virtual machines and power on them on.

Justification

1. Stretched Clusters are more suited to Disaster Avoidance than Disaster Recovery
2. Avoids complex and manual  intervention in the case of a disaster in the case of a stretched cluster solution
3. A Stretched cluster provides minimal control in the event of a Disaster where as in this case, HA simply restarts VMs once the storage is presented (automatically) and the hosts are taken out of Maintenance mode (also automated)
4. Having  two (2) ESXi hosts for the vCloud resource cluster setup in “Datacenter B” in “Maintenance Mode” and the storage mirrored as discussed  allows the virtual workloads to be recovered in an automated fashion as part of the VMware Site Recovery Manager solution.
5. Removes the management overhead of managing a strecthed cluster using features such as DRS affinity rules to keep VMs on the hosts on the same site as the storage
6. vSphere 5.1 backed resource clusters support >8 host clusters for “Fast provisioning”
7. Remove the dependency on the Metropolitan Area Data and Storage networks during BAU and the potential impact of the latency between sites on production workloads
8. Eliminates the chance of a “Split Brain” or a “Datacenter Partition” scenario where VM/s can be running at both sites without connectivity to each other
9. There is no specific requirement for non-disruptive mobility between sites
10. Latency between sites cannot be guaranteed to be <10ms end to end

Alternatives

1. Stretched Cluster between “Datacenter A” and “Datacenter B”
2. Two independent vCloud deployments with no automated DR
3. Have more/less hosts at the DR site in the same configuration

Implications

1. Two (2) ESXi hosts in the vCloud Cluster located in “Datacenter B” will remain unused as “Hot Standby” unless there is a declared site failure at “Datacenter A”
2. Requires two (2) vCenter servers , one (1) per Datacenter
3. There will be no non-disruptive mobility between sites (ie: vMotion)
4. SRM protection groups / plans need to be created/managed Note: This will be done as part of the Production cluster
5. In the event of a DR event, only half the compute resources will be available compared to production.
6. Depending on the latency between sites, storage performance may be reduced by the synchronous replication as the write will not be acknowledged to the VM at “Datacenter A” until committed to the storage at “Datacenter B”

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