AIM Buffers

Information about AIM buffers:

A buffer is a volume (with a drive letter), or a directory within a volume, accessible from the local computer.

The AIM software uses standard NTFS space to buffer data replication on source and destination servers. For each volume you are replicating with AIM, a unique folder is created which will contain a set of replication files (including block-level writes to be replicated, timestamp, and sequence information).

On the source server, the buffer is necessary to accumulate the changes until the data is transferred to the destination server.

On the destination server, the buffer collects incoming replication files to make sure data changes are destaged in order. This is critical in the event that the replication files arrive out of order or the destination volume goes offline. Information will continue to accumulate until it can be processed.

The same server can be configured as both source and destination.

Consider the following when sizing and creating buffers:

  • Do not create or use AIM buffers on the boot drive.

  • Use a dedicated local disk for the AIM buffer. Do not use a disk mapped from a DataCore storage server.

  • For performance purposes, your AIM buffers should not reside on any disk you wish to “AIM.”

  •  We highly recommend using a dedicated partition to avoid contention with other system or application files if the buffer reaches capacity.
     When creating your buffers in Windows Disk Management, you can use the Quick Format option. Label the partition something meaningful, such as AIM [Src/Dest] Buffer Volume in order to distinguish the partition.

  • Adequate disk space is necessary to accommodate the size of your buffers.

  • Buffers must be sized to accommodate the amount of data transferred routinely. Large buffers can absorb more data and transfer delays and latencies that may occur over the network. The buffer partitions should be at least the size of the largest disk you plan to initialize.

  • A server operating as both a source and destination can use a common buffer, but it must be sized as the sum of the size of both buffers.

  • Size the source buffer after considering the possibility of IP link downtime between the source and destination servers. The appropriate size of a buffer is determined by multiplying the amount of data that is expected to be transferred daily by the maximum allowable IP link downtime.

For example, your IP link goes down over a weekend. If your source system sends 500 MB/day and the IP link downtime could go uncorrected for two days, create a source buffer that is at least 1GB (or 500 MB/day x 2 days).  

If your link goes down and buffer space becomes inadequate to support the data transfers, AIM will log changes and perform log-based recovery of change blocks that exceeded the buffer space after the IP link is restored. The best practice is to size the buffer up.

  • If the source buffer is unavailable to the source server, the source buffer may have reached maximum capacity. If this occurs, a warning appears in the Event Log. If this happens often, increase the size of the source buffer. Recommendation: make the buffer a Windows dynamic disk so it can be easily expanded.

  • Changes to the destination buffer can only be performed before AIM sets are created. In order to alter the destination buffer after AIM sets are created, the AIM sets must be deleted before the buffer can be changed. Refer to Deleting AIM Set Associations for additional information.

Related Topics:

AIM Initialization Time Estimates

Changing Source Buffer Settings

Changing Destination Buffer Settings

 

AIM Buffers