Types of dynamic volumes
A volume created from free space on a single physical disk. It can consist of one region on the disk or several regions, virtually united by the Logical Disk Manager (LDM). It provides no additional reliability, no speed improvement, nor extra size.
A volume created from free disk space virtually linked together by the LDM from several physical disks. Up to 32 disks can be included into one volume, thus overcoming the hardware size limitations, but if at least one disk fails, all data will be lost, and no part of a spanned volume may be removed without destroying the entire volume. So, a spanned volume provides no additional reliability, nor a better I/O rate.
A volume, also sometimes called RAID 0, consisting of equal sized stripes of data, written across each disk in the volume; it means that to create a striped volume, a user will need two or more dynamic disks. The disks in a striped volume don’t have to be identical, but there must be unused space available on each disk that you want to include in the volume and the size of the volume will depend on the size of the smallest space. Access to the data on a striped volume is usually faster than access to the same data on a single physical disk, because the I/O is spread across more than one disk.
Striped volumes are created for improved performance, not for their better reliability – they do not contain redundant information.
A fault-tolerant volume, also sometimes called RAID 1, whose data is duplicated on two identical physical disks. All of the data on one disk is copied to another disk to provide data redundancy. Almost any volume can be mirrored, including the system and boot volumes, and if one of the disks fails, the data can still be accessed from the remaining disks. Unfortunately, the hardware limitations on size and performance are even more severe with the use of mirrored volumes.
A fault-tolerant volume, also sometimes called RAID 1+0, combining the advantage of the high I/O speed of the striped layout and redundancy of the mirror type. The evident disadvantage remains inherent with the mirror architecture – a low disk-to-volume size ratio.
A fault-tolerant volume whose data is striped across an array of three or more disks. The disks do not need to be identical, but there must be equally sized blocks of unallocated space available on each disk in the volume. Parity (a calculated value that can be used to reconstruct data in case of failure) is also striped across the disk array. And it is always stored on a different disk than the data itself. If a physical disk fails, the portion of the RAID-5 volume that was on that failed disk can be re-created from the remaining data and the parity. A RAID-5 volume provides reliability and is able to overcome the physical disk size limitations with a higher than mirrored disk-to-volume size ratio.