PowerScale OneFS 9.2.1.0 CloudPools Administration Guide

CloudPools limitations and expected behaviors

During normal CloudPools operation, you should be aware of the following limitations and expected behaviors.

Rolling upgrade before CloudPools usage

If you are performing a rolling upgrade to a OneFS 8.2.x version, and intend to use CloudPools for the first time, wait until the upgrade and commit complete. By waiting for the upgrade to complete, you start using CloudPools with the most recent CloudPools upgrades. Upgrades to newer versions of the CloudPools stub files (SmartLink files) are not required.

Cloud storage account deletion

CAUTION Do not delete a cloud storage account that is in use by archived files.

Doing so can lead to data loss or unavailability for the archived files that use the deleted account. Any attempt to open SmartLink files that are associated with a deleted account fails with I/O error messages. In addition, NDMP backup and restore and SyncIQ failover and failback fail when a related cloud storage account is deleted.

If an NFS or SMB user attempts to open a SmartLink file for inline access and receives an I/O error, it may indicate that the related cloud storage account was deleted.

Dell recommends trying inline access of other SmartLink files in the same CloudPool. If the same error is generated for those files, it means that the cloud storage account is deleted and data is lost. If the other SmartLink files are accessible, the SmartLink file that generated the error might be corrupted. Either way, contact Technical Support for assistance.

Accessing SmartLink files

You can view and modify cloud data by accessing SmartLink files.

SmartLink file timestamps

Opening a SmartLink file through a supported protocol can change the timestamp data. When a file is first archived and the SmartLink file is created, the ctime timestamp stays the same as the timestamp on the original file. However, the first time the SmartLink file is opened (inline access), the ctime timestamp changes because a cache component is added to the file.

Inline access can appear to convert a SmartLink file to a regular file

When a user accesses a SmartLink file on the PowerScale cluster using a supported protocol, the file opens in an application on the client system. During this process, called inline access, most applications support the creation of a CloudPools cache from which users can view and modify archived data. With inline access, the SmartLink file remains intact on the cluster. Modifications that the user makes to file data are stored in the cache and updated to the cloud.

However, some applications do not support inline access. Instead, these applications create a copy of the original file apart from the SmartLink file. The new file, containing all original file data, is given a new logical I-node (LIN) number and timestamps that differ from the file that was originally archived. This behavior has been observed in only a few programs, including Microsoft Office applications. In these cases, an entirely new file is created. The original SmartLink file and its associated data in the cloud is tagged for removal (garbage collection).

If the new file meets the criteria of the file pool policy that archived the original file to the cloud, the new file is archived the next time the SmartPools job runs. A new SmartLink file is created in its place on the local cluster. If the new file does not meet the policy criteria, the full file remains on the cluster.

For best results using CloudPools, Dell recommends that you avoid archiving files that users are still actively modifying.

Client-based tools and SmartLink files

If you run a client-based tool such as AVScan (anti-virus scan) or a backup application, file data in the cloud is fully cached back to the SmartLink files. This activity can result in heavy network usage and increased service provider costs, and negates space saving on your cluster.

Expired SmartLink files

Expired SmartLink files are not restored using NDMP and do not synch back using SyncIQ. A SmartLink file on an NDMP backup or on a SyncIQ secondary (target) cluster is expired when either of the following is true:

• The original SmartLink file is deleted from the primary (source) cluster.
• The original file data in the cloud is fully recalled.

Recall interrupted

When a full cache is in process (that is, someone performed an inline access of a SmartLink file), recall of the same file can fail. The full cache is allowed to complete first, and the user should retry the recall after caching is completed.

ADS files

CloudPools does not archive and recall ADS (alternate data stream) files.

SMB Oplock

SMB Oplock (lease/notification) does not work in cases where you create a file with the SUPERCEDE flag, the file already exists, and is archived.