Implementing Virtual Provisioning using SYMCLI


1.    Planning

2.    Create Thin Devices (TDEV)

3.    Create Data Devices

4.    Create Thin Pool

5.    Add Data Devices to Thin Pool

6.    Bind TDEV to pool

7.    Map and mask TDEV

8.    Monitor TDEV allocation and thin pool




Create Thin Devices:



Display Newly Created Thin Devices:

Ÿ  Thin devices will be in a Not Ready state until bound to a thin pool

Ÿ  No back-end resources are allocated



Create Data Devices:





























Display Data Devices:


Create Thin Pool:

Ÿ  Thin pools can be created at the same time as data devices or performed in separate operations

Ÿ  There is no default thin pool, only user defined pools



Add Data Devices to Pool:

Ÿ  Data devices can be added to a thin pool at time of creation

Ÿ  A data device must be enabled before being used for allocation

         Can be performed in a separate operation




Display Thin Pool:

         State of thin pool is Enabled as soon as one data device is enabled

         Currently no devices are bound and thus no tracks have been allocated


Detailed Information about Pool:

Bind Thin Devices to Thin Pool:

Ÿ  TDEV must be bound to a thin pool before use

         May be bound to a thin pool at time of creation

Ÿ  The first extents are allocated to the TDEV when bound

         Preallocation reduces risk of failure due to over subscription

Bound Devices:

Ÿ  After binding, one extent (12 Tracks) are allocated to each TDEV


Thin Pool After Binding TDEVs Data Devices

TDEVs after Mapping and Masking:


Round Robin Allocation:


Fill up Pool Before adding Datadevs:


Add Data Devices That Are Not Currently Pooled:


Enable Devices and Write More Data:

Thin Metadevice Creation:

Ÿ  Created using thin devices before binding devices to pool


symdev show on Thin Meta Device:

Bind Meta Device to Pool:


Concatenate Members to Bound Meta:


Unbinding Thin Devices:

Ÿ  Before unbinding thin Devices must be unmapped or set NR

Ÿ  In the list above the meta device is unmapped while the regular TDEVs are mapped and RW



Pool Space freed up after unbinding of TDEVs:

Set Subscription Limit:


Enforcement of Subscription Limit:

Ÿ  Thin Devices 103-106 were created with 1GB capacity

Ÿ  Meta device 107 has 4 GB capacity

Ÿ  Devices 103:107 together exceed the 150% subscription limit


Draining of Data Devices in 5874:

Ÿ  Thin pools can be shrunk non-disruptively

Ÿ  Allocated thin device extents on DATA devices will be drained from a DATA device when it is disabled

         Extents get written to enabled devices in the pool

Ÿ  Up to 20% of the pool space can be disabled and drained at one time, i.e.

         There have to be at least 5 devices in the pool for one of the devices to be disabled and removed from the pool


Draining DATA Devices:

Ÿ  The pool sun180 has 5 enabled devices, each with allocated extents

Ÿ  Disabling a DATA device causes it to drain

Ÿ  Disabled DATA device will enter a draining state while its allocated extents are written to the remaining enabled devices in the pool

Ÿ  After the drain has completed, the device is now disabled

Ÿ  It can now be removed from the pool


Key points covered in this module:

Ÿ  Creation of Thin and Data Devices

Ÿ  Addition of Data Devices to Thin Pools

Ÿ  Binding Thin Devices to Thin Pools

Ÿ  Creation and binding of Thin Meta Devices to a Thin Pool

Ÿ  Unbinding of Thin Devices to free up pool space

Ÿ  Setting of pool subscription limit

Ÿ  Non-disruptive draining of Data Devices