Core sizing guidelines
The main considerations for sizing your Core deployment are as follows:
• Total data set size—The total space used across LUNs (not the size of the LUNs).
• Total number of LUNs—Each LUN adds five optimized connections to the SteelHead. Also, each branch office in which you have deployed Edge represents at least one LUN in the storage array.
• RAM requirements—You should have at least 700 MB of RAM per terabyte (TB) of used space in the data set. There is no specific setting on the Core to allocate memory on this basis, but in general this amount is how much the Core uses under normal circumstances if the memory is available. Each Core model has a fixed capacity of memory (see the product and SteelHead specification sheets for details) that it is shipped with. If the metric falls below the recommended value, performance of the Core can be affected, and the ability to efficiently perform prediction and prefetch operations.
Other potentially decisive factors include:
• Number of files and directories
• Type of file system, such as NTFS or VMFS
• File fragmentation
• Active working set of LUNs
• Number of misses seen from Edge
• Response time of the storage array
if you are applying configuration changes where additional LUNs or Edges are in the process of being added, the Core will prevent the operation from being performed if the specification limits will be exceeded. The administrator will receive a warning message describing the problem, such as exceeding the maximum number of LUNs or exceeding the number of Edges.
The specification enforcement does not apply to local LUNs. If an existing LUN is resized to a capacity that will exceed the specification limit for the Core, it will be allowed, but an alarm will be raised.
When a failover occurs in a Core HA deployment, the ActiveSolo Core will take control of serving the failed Core’s LUNs to the Edges it was connected to. This is normal behavior. Depending on the configuration in this scenario, if the Cores are running software version 5.0 or later, the ActiveSolo Core could be in a situation where the total number of LUNs and/or Edges exceed the specification. This is due to it taking over from the failed Core. If the specification limits are exceeded, an alarm will be raised on the ActiveSolo Core but operations will continue. The alarm will clear automatically once the failed Core is recovered and back online.
There is currently no enforcement for Edge devices deployed in block storage mode.