Understand the key terminologies relating to Content Software for File system capacity management and the formula for calculating the Content Software for File system net data storage capacity
- Raw capacity
- Raw capacity is the total capacity on all the SSDs assigned to a Content Software for File system cluster. For example, ten SSDs of one terabyte each have a total raw capacity of ten terabytes. This is the total capacity available for the Content Software for File system. This will change automatically if more servers or SSDs are added.
- Net capacity
- Net capacity is the space for user data on the SSDs in a configured Content Software for File system. It is based on the raw capacity minus the Content Software for File filesystem overheads for redundancy protection and other needs. This will change automatically if more servers or SSDs are added.
- Stripe width
- The stripe width is the number of blocks with a common protection set ranging from 3 to 16. The Content Software for File system has distributed any-to-any protection. Consequently, in a system with a stripe width of 8, many groups of 8 data units spread on various servers protect each other (rather than a group of 8 servers forming a protection group). The stripe width is set during the cluster formation and cannot be changed. Stripe width choice impacts performance and space.
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Note: If not configured, the stripe width is set automatically to #Failure Domains - Protection Level
- Protection level
- The protection level is the number of additional protection blocks added to each stripe, which can be either 2 or 4. A system with a protection level of 2 can survive 2 concurrent failures. In comparison, system data with a protection level of 4 is protected against any concurrent 4 server/disk failures, and its availability is protected against any 4 concurrent disk failures or 2 concurrent server failures. A high protection level has space and performance implications. The protection level is set during the cluster formation and cannot be changed.
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Note: If not configured, the data protection drives in the cluster stripes are automatically set to 2.
- Failure domains (optional)
- A failure domain is a group of Content Software for File servers that can fail concurrently due to a single root cause, such as a power circuit or network switch failure.
- A cluster can be configured with explicit or implicit failure domains. In a cluster with explicit failure domains, each group of blocks that protect each other is spread on different failure domains.
- In a cluster with implicit failure domains, the group of blocks is spread on different servers, and each server is a failure domain. Additional failure domains can be added, and new hosts can be added to any existing or new failure domain.
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Note: This documentation relates to a homogeneous Content Software for File system deployment. That is, the same number of servers per failure domain (if any) and the same SSD capacity per server. For information about heterogeneous Content Software for File system configurations, contact customer support.
- Hot spare
- A hot spare is the number of failure domains that the system can lose, undergo a complete rebuild of data, and still maintain the same net capacity. All failure domains are constantly participating in storing the data, and the hot spare capacity is evenly spread within all failure domains.
- The higher the hot spare count, the more hardware required to obtain the same net capacity. On the other hand, the higher the hot spare count, the more relaxed the IT maintenance schedule for replacements. The hot spare is defined during cluster formation and can be reconfigured anytime.
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Note: If not configured, the hot spare is automatically set to 1.
- Content Software for File filesystem overhead
- After deducting the protection and hot spare capacity, only 90% of the remaining capacity can be used as net user capacity, with the other 10% of capacity reserved for the Content Software for File filesystems. This is a fixed formula that cannot be configured.
- Provisioned capacity
- The provisioned capacity is the total capacity assigned to filesystems. This includes both SSD and object store capacity.
- Available capacity
- The available capacity is the total capacity used to allocate new filesystems, net capacity minus provisioned capacity.