Adaptec 3805和越来越多的卡开始支持 RAID1E 和 RAID5EE 及 RAID6
1，RAID 1E
RAID 1E是RAID 1的增强版本，它并不是我们通常所说的RAID 0+1的组合。RAID 1E的工作原理与RAID1基本上是一样的，只是RAID 1E至少需要3块硬盘才能实现。RAID 1E和RAID 1的工作原理图如下：
 可以把RAID1理解成盘与盘之间的镜像，而RAID1E是条带与条带之间的镜像，明显的好处是3块盘也可以做array了，他们都只允许坏一块盘，而RAID1E性能要好点（实际情况还要取决卡的优劣）。
2,RAID 5EE
RAID 5EE是在每个磁盘中预留一部分空间作为分布的热备盘，当一个硬盘出现故障时，这个磁盘上的数据将被压缩到分布的热备盘中，达到数据的保护作用。不过与RAID 5E不同的是RAID 5EE内增加了一些优化技术，使RAID 5EE的工作效率更高，压缩数据的速度也更快。RAID 5EE允许两个磁盘出错，最少需要4个磁盘实现。
RAID 5EE，可以理解成原先的RAID5+SPARE盘模式，只是把SPARE盘的空间条带化并且分布在每块硬盘上，这样一来，SPARE盘也参与读写，性能比RAID5要提高一点，而且在坏了一块盘时恢复也比RAID5快。RAID5有compact和expand模式，expand模式坏掉一块硬盘后，RAID5EE会自动转变为compact模式，在compact模式还可以允许一块盘故障。
 RAID 5EE Disk Array
需要注意的是，RAID5EE不能同时坏两块盘；
坏一块盘以后，RAID5EE会自动修复到compact模式，
相当于RAID5；自动修复完成后，才可以再坏一块，
这样一共可以坏两块，但不能同时坏。
如RAID5EE坏了1块盘，自动修复到compact模式以后又坏了一块，
修复方式如下：
先手工添加一块spare盘进行修复到compact模式，
再手工添加一块spare盘继续修复到expand模式。
3,RAID 6
RAID 6是由一些大型企业提出来的私有RAID级别标准，它的全称叫“Independent Data disks with two independent distributed parity schemes（带有两个独立分布式校验方案的独立数据磁盘）”。这种RAID级别是在RAID 5的基础上发展而成，因此它的工作模式与RAID 5有异曲同工之妙，不同的是RAID 5将校验码写入到一个驱动器里面，而RAID 6将校验码写入到两个驱动器里面，这样就增强了磁盘的容错能力，同时RAID 6阵列中允许出现故障的磁盘也就达到了两个，但相应的阵列磁盘数量最少也要4个。
每个磁盘中都具有两个校验值，而RAID 5里面只能为每一个磁盘提供一个校验值，由于校验值的使用可以达到恢复数据的目的，因此多增加一位校验位，数据恢复的能力就越强。不过在增加一位校验位后，就需要一个比较复杂的控制器来进行控制，同时也使磁盘的写能力降低，并且还需要占用一定的磁盘空间。因此，这种RAID级别应用还比较少，相信随着RAID 6技术的不断完善，RAID 6将得到广泛应用。RAID 6的磁盘数量为N+2个。
RAID 6 Disk Array
需要注意的是，Adaptec3805 RAID6可以同时坏两块硬盘，在修复的时候，是一块一块的修复的。RAID6的性能和RAID5EE相当。
4,RAID 60 (Striping and striping with dual party)
Combines multiple RAID 6 sets with RAID 0 (striping). Dual parity allows the failure of two disks in each RAID 6 array. Striping helps to increase capacity and performance without adding disks to each RAID 6 array (which would decrease data availability and could impact performance in degraded mode).
 RAID 60 Disk Array
|
Features |
RAID 0 |
RAID 1 |
RAID 1E |
RAID 5 |
RAID 5EE |
|
Minimum # Drives |
2 |
2 |
3 |
3 |
4 |
|
Data Protection |
No Protection |
Single-drive failure |
Single-drive failure |
Single-drive failure |
Single-drive failure |
|
Read Performance |
High |
High |
High |
High |
High |
|
Write Performance |
High |
Medium |
Medium |
Low |
Low |
|
Read Performance (degraded) |
N/A |
Medium |
High |
Low |
Low |
|
Write Performance (degraded) |
N/A |
High |
High |
Low |
Low |
|
Capacity Utilization |
100% |
50% |
50% |
67% - 94% |
50% - 88% |
|
Typical Applications |
High End Workstations, data logging, real-time rendering, very transitory data |
Operating System, transaction databases |
Operating system, transaction databases |
Data warehousing, web serving, archiving |
Data warehousing, web serving, archiving |
|
Features |
RAID 6 |
RAID 10 |
RAID 50 |
RAID 60 |
|
Minimum # Drives |
4 |
4 |
6 |
8 |
|
Data Protection |
Two-drive failure |
Up to one disk failure in each sub-array |
Up to one disk failure in each sub-array |
Up to two disk failure in each sub-array |
|
Read Performance |
High |
High |
High |
High |
|
Write Performance |
Low |
Medium |
Medium |
Medium |
|
Read Performance (degraded) |
Low |
High |
Medium |
Medium |
|
Write Performance (degraded) |
Low |
High |
Medium |
Low |
|
Capacity Utilization |
50% - 88% |
50% |
67% - 94% |
50% - 88% |
|
Typical Applications |
Data archive, backup to disk, high availability solutions, servers with large capacity requirements |
Fast databases, application servers |
Large databases, file servers, application servers |
Data archive, backup to disk, high availability solutions, servers with large capacity requirements |
Types of RAID
|
Types of RAID |
Software-Based |
Hardware-Based |
External Hardware |
|
Description |
Best used for large block applications such as data warehousing or video streaming. Also where servers have the available CPU cycles to manage the I/O intensive operations certain RAID levels require.
Included in the OS, such as Windows®, Netware, and Linux. All RAID functions are handled by the host CPU which can severely tax its ability to perform other computations. |
Best used for small block applications such as transaction oriented databases and web servers.
Processor-intensive RAID operations are off-loaded from the host CPU to enhance performance.
Battery-back write back cache can dramatically increase performance without adding risk of data loss. |
Connects to the server via a standard controller. RAID functions are performed on a microprocessor located on the external RAID controller independent of the host. |
|
Advantages |
Low price
Only requires a standard controller |
Data protection and performance benefits of RAID
More robust fault-tolerant features and increased performance versus software-based RAID |
OS independent
Build high-capacity storage systems for highend servers |
|
解决方案
