Prior to the concept of storage pools, data corresponding to a VDisk was stored on any available configured physical disks. Sometimes however there is a need to categorize disks such that data corresponding to a VDisk is stored only on a specific set of disks. Such a set of disks is termed as a Storage Pool.
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)
5. Select "Enable logs" if this pool needs to maintain its own logs (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
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 and also log data for other pools.
Enabling dedupe metadata and logs for a pool
Deduplication tables and log information are written to 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 and log information on 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. Similar logic applies for the logs. If a pool depends on the Default pool for either data deduplication tables or log information then atleast one disk needs to be configured for the Default pool.
Memory available in the system play a major role in the number of pools that can maintain their own deduplication tables and logs. In general for every 2GB of memory available, 2 pools can maintain their own deduplication tables and only 1 pool can maintain log information.
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)