Configuring Storage Pools

With Pools, physical disks and VDisks can be configured to belong to a specific pool. For example there can be a SSD pool and all SSD disks can be configured for this pool. VDisks created can be then be configured to use this pool and any data corresponding to the VDisk will be written to any available SSD disk within the SSD pool.

Creating a new Storage Pool

1. Click on "Storage Pools" menu

2. Click on the "Add Pool" button.

3. In the "Add Storage Pool" form shown enter the name of the pool to be created

4. Select "Enable dedupe metadata" if this pool needs to maintain its own metadata (described further below)

6. Click on submit

Once a pool is created, to add a disk or a VDisk to this pool, select the pool when adding the disk or creating a VDisks

"Default" pool

The Default pool is a system defined pool and cannot be deleted. The Default pool is special in that a disk configured for the default pool can hold deduplication tables for other pools.

Enabling dedupe metadata for a pool

Deduplication tables need to be stored on disk. Each pool (including the default) would have a master disk. The master disk is the first disk configured for that pool.

A pool can maintain deduplication tables its own master disk or on the master disk of the "Default" pool. If "Enable dedupe metadata" is selected when creating a pool, the pool will maintain its own deduplication tables else the master disk from the "Default" pool is used. If a pool depends on the Default pool for the data deduplication tables then the Default pool needs to have a disk configured first.

There is a limit on the number of pools which can maintain their own deduplication tables. By default the maximum number of pools which can maintain the deduplication metadata is one The preferred approach is to configure a disk in the Default pool. The Default pool will then be used to maintain the deduplication tables for all other storage pools.

The number of pools which can maintain the deduplication metadata can be extended by the following steps

Edit /quadstor/etc/quadstor.conf and add the following line (create the file if required)
SequentialTables=0

service quadstor restart
If more than one pools needs to maintain its own deduplication metadata "SequentialTables=0" must be set in quadstor.conf prior to adding any disk to any of the storage pools

Impact of Pools on deduplication

Pools have a significant impact on deduplication ratio. For example, lets assume two VDisks VDisk 'A' and 'B' are configured in the system. VDisk 'A' however belongs to Pool 'A' and VDisk 'B' belongs to Pool 'B'. Even if VDisk 'B' receives data which is identical to that on VDisk 'A', the data cannot be deduplicated as VDisk 'A' and 'B' belong to different pools.

Listing currently configured pools

The currently configured pools can be view by clicking on the "Storage Pools" menu.

The "Disks" column indicates the number of physical disks configured for the Pool.

Similarly the "VDisks" column indicates the number of VDisks configured in that pool.

Click on the "View" link to change a pool name, list the physical disks for configured for a pool and also the pool disk usage statistics

In order to change the default pool name add the following line to /quadstor/etc/quadstor.conf (create it if required)

DefaultPool=<new name>

For example

DefaultPool=NewPool