Dell PowerVault MD3220 CLI Guide - Page 127

Segment Size The size of a segment determines how many data blocks that the RAID controller module writes on a single physical disk in a virtual disk before writing data on the next physical disk. Each data block stores 512 bytes of data. A data block is the smallest unit of storage. The size of a segment determines how many data blocks that it contains. For example, an 8 KB segment holds 16 data blocks. A 64 KB segment holds 128 data blocks. When you enter a value for the segment size, the value is checked against the supported values that are provided by the RAID controller module at run time. If the value that you entered is not valid, the RAID controller module returns a list of valid values. Using a single physical disk for a single request leaves other physical disks available to simultaneously service other requests. If the virtual disk is in an environment where a single user is transferring large units of data (such as multimedia), performance is maximized when a single data transfer request is serviced with a single data stripe. A data stripe is the segment size that is multiplied by the number of physical disks in the disk group that are used for data transfers. In this case, multiple physical disks are used for the same request, but each physical disk is accessed only once. For optimal performance in a multiuser database or file system storage environment, set your segment size to minimize the number of physical disks that are required to satisfy a data transfer request. Security Type The securityType parameter is valid for physical disks that are capable of self encrypting disk (SED). With SED, the RAID controller module firmware can create a key and activate the physical disk security feature. The physical disk security feature encrypts data as the data is written to the physical disk and decrypts the data as the data is read from the physical disk. Without the key created by the RAID controller module, the data written to the physical disk is inaccessible. Before you can set the securityType parameter to capable or enabled, you must create a storage array security key. Use the create storageArray securityKey command to create a storage array security key. The following commands are related to the securtiy key: • create storageArray securityKey • set storageArray securityKey Script Commands 127