Chapter 2. LVM-VDO requirements

RAM requirements for VDO volumes include memory allocation for the VDO module and the Universal Deduplication Service (UDS) to optimize storage efficiency.

Each VDO volume has two distinct memory requirements:

UDS sparse and dense index types differ in memory usage, deduplication window coverage, and physical space requirements, affecting optimal workload selection strategies.

The UDS Sparse Indexing feature relies on the temporal locality of data. It attempts to retain only the most relevant index entries in memory. With the sparse index, UDS can maintain a deduplication window ten times larger than the dense index while using the same memory size. The sparse index requires ten times more physical space for metadata.

Although the sparse index provides the greatest coverage, the dense index provides more deduplication advice. For most workloads, given the same memory size, the difference in deduplication rates between dense and sparse indexes is negligible.

You can configure a VDO volume to use up to 256 TB of physical storage. Only a certain part of the physical storage is usable to store data.

VDO requires storage for two types of VDO metadata and for the UDS index. Use the following calculations to determine the usable size of a VDO-managed volume:

VDO system requirements vary by physical volume size and deployment type. Specific RAM and disk usage examples cover primary storage and backup storage scenarios.

The following tables provide approximate system requirements of VDO based on the physical size of the underlying volume. Each table lists requirements appropriate to the intended deployment, such as primary storage or backup storage.

The exact numbers depend on your configuration of the VDO volume.

You must place certain storage layers under a VDO logical volume and others on top of it.

You can place thick-provisioned layers on top of VDO, but you cannot rely on the guarantees of thick provisioning in that case. As the VDO layer is thin-provisioned, the effects of thin provisioning apply to all layers. If you do not monitor the VDO volume, you might run out of physical space on thick-provisioned volumes on top of VDO.

As the supported placement of the following layers is under VDO, do not place them on top of VDO:

The following configurations are not supported:

Virtual Data Optimizer (VDO) can be deployed on Logical Volume Manager (LVM) in various scenarios to provide deduplicated storage solutions. These scenarios include Kernel-based Virtual Machine (KVM), file systems, Internet Small Computer Systems Interface (iSCSI) targets, and encryption configurations.

You can deploy VDO on LVM (LVM-VDO) in a variety of ways to provide deduplicated storage for:

LVM-VDO exposes its deduplicated storage as a regular logical volume (LV). You can use it with standard file systems, iSCSI, File Context (FC) target drivers, or unified storage.