HP StoreAll Storage - Manual (Page 160)

Rebalancing a file system that is configured for Object Store
Any time a file system configured for Object Store is expanded or storage is removed, you must
run the rebalance operation on the account, container, and object components of the Object Store
(A/C/O). The only exception is if you have already ensured that each node has equal storage;
then there is no need to run the rebalance operation.
By default, Object Store assigns a weight of 100 to each node folder created under Object Store.
Each node folder represents a device whose size equals the total size of the segments mapped to
that specific node. When segments are added to or removed from a node configured for Object
Store, it may result in uneven distribution of data across the segments. If even distribution is preferred,
you must manually reset the weight of the device of the node that owns the new segments using
the swift-ring-builder command and then perform the rebalance operation on the account, container,
and object components (A/C/O). The rebalance operation rebalances all partitions, causing data
movement across different devices. Therefore, the rebalance operation requires down time for the
Object Store.
For example, there are three couplets, with sizes and weights as follows:
Weight Size Couplet
100 1 TB A
100 1 TB B
50 500 GB C
Using Couplet B for this example, there are two nodes in the couplet and each contains 1 TB of
storage. As shown in the output of step 1a., each node is assigned a weight of 100. If a 1 TB LUN
is added to only one node in Couplet B, that node would now be assigned a weight of 200 as
indicated in the following table of changed sizes and weights:
Weight Size Couplet
100 1 TB A
200 2 TB B
50 500 GB C
The following steps illustrate how to perform the rebalance for this example.
To perform the rebalance:
160 Using Object Store