Unexpected volume full conditions can occur with iSCSI LUs, as illustrated by the following two examples:
- Directly Attached Disks. When a client uses a directly attached disk, it can monitor the amount of available free space. If a partition contains no free space, the client can return a Volume Full condition. In this way, the client can ensure against file system corruption due to running out of disk space part way through an operation.
- iSCSI LU. By way of background, on iSCSI LUs with snapshots enabled, old data is preserved, not overwritten. Therefore, overwriting an area of an LU causes the server to allocate extra disk space, while using no extra disk space within the client's partition, causing a Volume Full condition to occur, even when partitions within the LU contain free space.
Under this scenario, a client may receive a Volume Full condition part-way through an operation, causing file system corruption. Although this corruption should be fixable, this situation should be avoided. Note: customer support recommends allocating sufficient disk space on the server to contain all iSCSI LUs and snapshots, as well as careful monitoring of free disk space.