See also: ZFS § ZFS's approach: RAID-Z and mirroring
#Softraid raid 6 software
Linux software RAID (Linux kernel's md driver) also supports creation of standard RAID 0, 1, 4, 5, and 6 configurations. In the examples above, k is the number of drives, while n#, f#, and o# are given as parameters to mdadm's -layout option. It is also possible to combine "near" and "offset" layouts (but not "far" and "offset"). For example, o2 layouts on two-, three-, and four-drive arrays are laid out as: 2 drives 3 drives 4 drives
#Softraid raid 6 driver
The md driver also supports an "offset" layout, in which each stripe is repeated o times and offset by f (far) devices. For a comparison, regular RAID 1 as provided by Linux software RAID, does not stripe reads, but can perform reads in parallel. "Far" layout performs well for systems in which reads are more frequent than writes, which is a common case. Random reads are somewhat faster, while sequential and random writes offer about equal speed to other mirrored RAID configurations. "Far" layout is designed for offering striping performance on a mirrored array sequential reads can be striped, as in RAID 0 configurations. For example, f2 layouts on two-, three-, and four-drive arrays would look like this: 2 drives 3 drives 4 drives All the chunks are repeated in each section but are switched in groups (for example, in pairs). The driver also supports a "far" layout, in which all the drives are divided into f sections. The two-drive example is equivalent to RAID 1. The four-drive example is identical to a standard RAID 1+0 array, while the three-drive example is a software implementation of RAID 1E. For example, an n2 layout on two, three, and four drives would look like: 2 drives 3 drives 4 drives
The standard "near" layout, in which each chunk is repeated n times in a k-way stripe array, is equivalent to the standard RAID 10 arrangement, but it does not require that n evenly divides k. The software RAID subsystem provided by the Linux kernel, called md, supports the creation of both classic (nested) RAID 1+0 arrays, and non-standard RAID arrays that use a single-level RAID layout with some additional features. A practical instance of this would use a small RAID 0 (stripe) volume for the operating system, program, and paging files second larger RAID 1 (mirror) volume would store critical data. Īs such, a Matrix RAID array can improve both performance and data integrity. The distinguishing feature of Matrix RAID is that it allows any assortment of RAID 0, 1, 5, or 10 volumes in the array, to which a controllable (and identical) portion of each disk is allocated. Matrix RAID supports as few as two physical disks or as many as the controller supports. Intel Matrix RAID (a feature of Intel Rapid Storage Technology) is a feature (not a RAID level) present in the ICH6R and subsequent Southbridge chipsets from Intel, accessible and configurable via the RAID BIOS setup utility. It does, however, prevent sharing the spare drive among multiple arrays, which is occasionally desirable. This spreads I/O across all drives, including the spare, thus reducing the load on each drive, increasing performance. RAID 5E, RAID 5EE, and RAID 6E (with the added E standing for Enhanced) generally refer to variants of RAID 5 or 6 with an integrated hot-spare drive, where the spare drive is an active part of the block rotation scheme. The performance penalty of RAID-DP is typically under 2% when compared to a similar RAID 4 configuration. RAID DP implements RAID 4, except with an additional disk that is used for a second parity, so it has the same failure characteristics of a RAID 6. RAID-DP is proprietary NetApp RAID implementation available only in ONTAP systems. However, it is fairly easy to calculate parity against multiple groups of blocks, one can calculate all A blocks and a permuted group of blocks. For example, in our graph both RAID 5 and 6 consider all A-labeled blocks to produce one or more parity blocks. Rather, double parity calculates the extra parity against a different group of blocks. Differently, the second set is not another set of points in the over-defined polynomial which characterizes the data. Now part of RAID 6, double parity (sometimes known as row diagonal parity ) features two sets of parity checks, like traditional RAID 6.
Diagram of a RAID-DP (double parity) setup
0 kommentar(er)
