RAID Subsystem – Very important topics when you implement Dynamics AX

With an Enterprise Resource Planning (ERP) system such as Microsoft Dynamics AX 2012, the database server generally stores a very large amount of important data for the business. If this data is unavailable for any length of time, the business could experience significant financial losses. Using a Redundant Array of Independent Disks (RAID) can help reduce the possibility of this loss from occurring. Another important aspect for a database server is fine tuning for optimal performance. A RAID disk subsystem can also be used to help achieve this goal.

RAID refers to a group of two or more disks managed as a single unit to store the data together with additional, or redundant, information to provide recovery if
there is a disk failure. Usually a failed disk in a RAID system can be replaced while the server is still running. This is one benefit of RAID.

NOTE: More Information on RAID can be found on the Microsoft MSDN web site.

Read/Write Performance:

Hardware RAID controllers divide read/writes of all data from Windows and applications such as Microsoft SQL Server into slices (usually 16 KB - 128 KB) that are spread across all disks participating in the
RAID array. Splitting data across physical drives distributes the read/write Input/Output (I/O) workload evenly across all physical hard disk drives participating in the RAID array. This increases disk I/O performance because the
disks participating in the RAID array are all kept equally busy, instead of some disks becoming a bottleneck because of irregular distribution of I/O requests.

Fault Tolerance: RAID provides protection from hard disk failure and accompanying data loss with two methods: mirroring and parity. There are many types of RAID configurations; each is called a RAID level, but only some RAID
levels are typically used with Microsoft Dynamics AX 2012.

RAID 0, which is not recommended for use with Microsoft Dynamics AX 2012, is typically defined as a group of striped disk drives, without parity or data redundancy. RAID 0 arrays deliver the best data storage efficiency and
performance of any array type.


RAID 1 is also known as disk mirroring. This is a pair of disk drives that store duplicate data, but appear to the computer as a single drive. All writes move to both drives of a mirrored pair so that the information on the drives is kept
identical. However, each drive can perform concurrent, independent read operations. Mirroring therefore doubles the read performance of a single nonmirrored drive, while the write performance is unchanged. RAID 1 delivers the
best performance of any redundant array type.


RAID 5 is also known as a Rotating Parity Array. RAID 5 works by striping data and parity across all the drives. Typically RAID 5 arrays offer similar read performance as pure striping, although writes are slower because the parity
information is updated every time. If one hard disk fails, it must be replaced with a new one of equal or larger size and it rebuilds from the parity on the remaining drives.


RAID 0+1
RAID 0+1, is a dual-level RAID and achieves a balance between the increased data availability of RAID 1, mirroring, and the increased read performance of RAID 0, striping. Do not to confuse RAID 0+1 with RAID 10, they work
differently and RAID 0+1 is what is recommended.


For maximum performance configure the database server shown in the following example:
• Two disk RAID 1 for the operating system and database software
• A small, four disk RAID 0+1, or two disk RAID 1 for database logs
• A larger RAID 0+1 for the main database files
o To reduce cost, swap out the RAID 0+1 for a RAID 5. However, this will result in slower performance.

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