File System
VOS supports a number of unique file types:
- Stream files: a stream of binary data, corresponding directly with the concept of a file on other operating systems.
- Fixed files: a sequence of records of a fixed size.
- Relative files: a sequence of records of a fixed file supporting random access
- Sequential files: a sequence of records of variable size
- Queue files: file-system based backup for message queues
- Pipes: named pipes for inter-process communication
- Transaction files: these provide support for journal based rollback
The VOS API allows the creation of multiple indexes per file, sorting according to the contents of a record, or an external key, or an internal key, or a well-defined set of multiple keys. A VOS file with one or more indexes can be used as a C-ISAM database table.
VOS uses a proprietary file naming syntax which includes the system name, module name, disk number, and directory, with components separated by the ">" symbol. Typically the system disk will be housed in the same module as the CPU, #m1, so a system file for a VOS cluster would be referenced as
VOS disk allocation and memory is organised in "blocks", each block being 4,096 bytes. Memory takes the form of RAM or paging. VOS systems support paging partitions and paging files. In modern versions of VOS, paging files can be created dynamically by the SysAdmin (but not removed without a reboot). These paging files can in theory consist of more than one extent (which is viewed by the kernel as a mini-paging partition) which may or may not be contiguous. However, non-contiguous extents are NOT recommended as they greatly increase disk activity. Admin should create the largest possible extent for the paging files as early as possible after the system has been booted.
Read more about this topic: Stratus VOS
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