Managing Avamar Server Capacity

The goal for an Avamar server is to reach a Steady State Capacity.  This is the point where backup initialization levels off and the amount of new data brought into the Avamar server is approximately the same as the space being freed by Garbage Collection.  Typically, Avamar will reach steady-state shortly after the longest retention period.

The OS View is the total file system in the Avamar, while the gsan View is the total allocated to stripes.  Gsan view is 65% of the Avamar server and it is used mainly for user data - this is the licensed capacity.  Above that, 20% of the system file space is used for checkpoint overhead and the remaining 15% is for the operating system.

Once the Avamar OS view reaches 65% utilization the Avamar becomes read-only.  The amount of primary data on clients, the initial backup commonality, day-over-day commonality and retention policies all affect utilization.

Checkpoint overhead is teh data that changes after a checkpoint is created.  When a checkpoint is created, it creates a read-only hard link to the strip.  When that data is modified, the maintains the read-only link and creates a new read/write stripe with the changed data.  Therefor, the longer checkpoints are created, the more disk is used because there is more read-only data located on the system.  Length of time checkpoints are retained is the largest contributing factor in checkpoint overhead, but how empty the stripes are, daily change rate and HFS checks not completing also contribute.

Capacity Threshold Warnings:
80% of user capacity = warning, start planning for expansion or cleanup
95% user capacity is the health check warning, new backups are suspended
100% user capacity makes the Avamar read-only, can still restore from server

85% of OS capacity = Garbage collection stops running, utilization increases rapidly
90% OS capacity = HFS checks stop running
96% OS capacity = no more checkpoints

At 95% health check warning, new backups are suspended and will not start again until the alert is acknowledged.

Monitor with Avamar Administrator or Enterprise Manager.  EM has the benefit of predictive analysis, so it can estimate system utilization rates.  It also has a graph showing daily change rate, which is a valuable tool in planning.

The DPN Summary in Avamar Administrator shows backup stats, including TotalByts which is all the modified and non-modified bytes being scanned for changes on the client, and ModSent which is the actual bytes sent over the wire.