Tag Archives: vswp

Example Architectural Decision – Virtual Machine Swap file location for SRM protected VMs

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Problem Statement

In an environment where multiple vSphere clusters are protected by VMware Site Recovery Manager (SRM) with array based replication. What is the best way to ensure the RTO/RPO is met/exceeded and to minimize the storage replication overhead?

Assumptions

1. Additional storage will not be obtained

2. Eight (8) Paths per LUN are Masked/Zoned

Motivation

1. Optimize underlying storage usage

2. Ensure transient files are not unnesasarily replicated

Architectural Decision

Configure vSphere cluster swapfile policy to Store the swapfile in the datastore specified by the host.

Create and configure a dedicated swap file datastores provided by Tier 1 storage with greater than the capacity of the total vRAM for the cluster itself, along with any/all clusters using the cluster/s as recovery sites.

Justification

1.Decreased storage replication between protected and recovery sites

2. Reduced impact to the underlying storage due to reduced replication

3. Reduces the used space at the recovery site

4. No impact to the ability to recovery to, or failback from the recovery site

5. vMotion performance will not be impacted as all hosts within a cluster share the same swap file datastore which is provided from the existing shared storage

6. There is minimal complexity in setting a dedicated swap file datastore as such, the benefits outweigh the additional complexity

7. In the event of swapping, performance will not be impacted as the swap file is on Tier 1 storage

8. There is no additional Tier 1 storage utilization as the vswap file would alternatively be set to “Store in the same director as the virtual machine”

9. Ensures memory (RAM) over commitment can still be achieved where as setting memory reservations would reduce/eliminate this benefit of vSphere

Implications

1. vMotion performance between clusters will be degraded as the swap file will be moved as part of the vMotion to the destination cluster swap file datastore

2. One (1) datastore out of a maximum of 256 per host are used for the swap file datastore

3. Eight (8) paths out of a maximum of 1024 per host are used for the swap file datastore

Alternatives

1. Store the swapfile in the same directory as the virtual machine

2. Set Virtual machine memory reservations of 100% to eliminate the vswap file

Relates Articles

1. Site Recovery Manager Deployment Location

2. VMware Site Recovery Manager, Physical or Virtual machine?

 

Example Architectural Decision – Memory Reservation for Virtual Desktops

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Problem Statement

In a VMware View (VDI) environment with a large number of virtual desktops, the potential Tier 1 storage requirement for vswap files (*.vswp) can make the solution less attractive from a ROI perspective and have a high upfront cost for storage. What can be done to minimize the storage requirements for the vswap file thus reducing the storage requirements for the VMware View (VDI) solution?

Assumptions

1. vSwap files are placed on Tier 1 shared storage with the Virtual machine (default setting)

Motivation

1. Minimize the storage requirements for the virtual desktop solution
2. Reduce the up front cost of storage for VDI
3. Ensure the VDI solution gets the fastest ROI possible without compromising performance

Architectural Decision

Set the VMware View Master Template with a 50% memory reservation so all VDI machines deployed have a 50% memory reservation

Justification

1. Setting 50% reservation reduces the storage requirement for vSwap by half
2. Setting only 50% ensures some memory overcommitment and transparent page sharing can still be achieved
3. Memory overcommitment is generally much lower than CPU overcommitment (around 1.5:1 for VDI)
4. Reserving 50% of a VDI machines RAM is cheaper than the equivalent shared storage
5. A memory reservation will generally provide increased performance for the VM
6. Reduces/Removes the requirement/benefit for a dedicated datastore for vSwap files
7. Transparent page sharing (TPS) will generally only give up to 30-35% memory savings

Implications

1. Less memory overcommitment will be achieved

Alternatives

1. Set a higher memory reservation  of 75% – This would further reduce the shared storage requirement while still allowing for 1.25:1 memory overcommitment
2. Set a 100% memory reservation – This would eliminate the vSwap file but prevent memory overcommitment
3. Set a lower memory reservation of 25% – This would not provide significant storage savings and as transparent page sharing generally only achieves upto 30-35% there would still be a sizable requirement for vSwap storage with minimal benefit
4. Create a dedicated datastore for vSwap files on lower Tier storage

 

Example Architectural Decision – Virtual Machine swap file location

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Problem Statement

When using shared storage where deduplication is utilized along with an array level snapshot based backup solution, what can be done to minimize the wasted capacity of snapping transient files in backups and the CPU overhead on the storage controller having to attempt to deduplicate data which cannot be deduped?

Assumptions

1. Virtual machine memory reservations cannot be used to reduce the vswap file size

Motivation

1. Reduce the snapshot size for backups without impacting the ability to backup and restore
2. Minimize the overhead on the storage controller for deduplication processing
3. Optimize the vSphere / Storage solution for maximum performance

Architectural Decision

1. Configure the HA swap file policy to store the swap file in a datastore specified by the host.
2. Create a new datastore per cluster which is hosted on Tier 1 storage and ensure deduplication is disabled on that volume
3. Configure all Host’s within a cluster to use the same specified datastore for vswap files
4. Ensure the new datastore is not part of any backup job

Justification

1. With minimal added complexity, backup jobs now exclude the VM swap file which reduces the backup size by the total amount of vRAM assigned to the VMs within the environment
2. As the vswap file is recreated at start up, loosing this file has no consequence
3. Decreasing Tier 1 storage requirements
4. The storage controller will not waste CPU cycles attempting to dedupe data which will not dedupe
5. Setting high percentages of memory reservation may impact the overcommitment in the environment where specifying a datastore for vswap reduces overhead without any significant downside

Implications

1. A datastore will need to be created for swapfiles
2. HA will need to be configured to store the swap file in a datastore specified by the host
3. The host (via Host Profiles) will need to be configured to use a specified datastore for vswap
4. vMotion performance will not be impacted where a VM is vMotion’d between two hosts that do not have a common vswap datastore as one datastore per cluster will be used for vswap files
5. The datastore will need to be sized to take into account the total vRAM assigned to VMs within the cluster

Alternatives

1. Set Virtual machine memory reservations of 100% to eliminate the vswap file
2. Store the swap file in the same directory as the virtual machine and accept the overhead on backups & dedupe
3. Use multiple datastores for vSwap across the cluster and accept the impact on vMotion