Chapter 2. LVM-VDO requirements

Each VDO volume has two distinct memory requirements:

The UDS Sparse Indexing feature relies on the temporal locality of data and attempts to retain only the most relevant index entries in memory. With the sparse index, UDS can maintain a deduplication window that is ten times larger than with the dense index while using the same amount of memory. 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 amount of memory, 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:

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. Since 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.

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

The following configurations are not supported:

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

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