As we know that we have different type of RAID but all the raid type are not suitable for the all application. We select raid type depending on the application and IO load/Usages. Actually there are so many factor involved before you select suitable raid type for any application. I am trying to give brief idea in order to select best raid type for any application. You can select raid type depending on your environment.

When to Use RAID 5
RAID 5 is favored for messaging, data mining, medium-performance media serving, and RDBMS implementations in which the DBA is effectively using read-ahead and write-behind. If the host OS and HBA are capable of greater than 64 KB transfers, RAID 5 is a compelling choice.
These application types are ideal for RAID 5:
1) Random workloads with modest IOPS-per-gigabyte requirements
2) High performance random I/O where writes represent 30 percent or less of the workload
3) A DSS database in which access is sequential (performing statistical analysis on sales records)
4) Any RDBMS table space where record size is larger than 64 KB and access is random (personnel records with binary content, such as photographs)
5) RDBMS log activity
6) Messaging applications
7) Video/Media

When to Use RAID 1/0
RAID 1/0 can outperform RAID 5 in workloads that use very small, random, and write-intensive I/O—where more than 30 percent of the workload is random writes. Some examples of random, small I/O workloads are:
1) High-transaction-rate OLTP
2) Large messaging installations
3) Real-time data/brokerage records
4) RDBMS data tables containing small records that are updated frequently (account balances)
5) If random write performance is the paramount concern, RAID 1/0 should be used for these applications.

When to Use RAID 3
RAID 3 is a specialty solution. Only five-disk and nine-disk RAID group sizes are valid for CLARiiON RAID 3. The target profile for RAID 3 is large and/or sequential access.
Since Release 13, RAID 3 LUNs can use write cache. The restrictions previously made for RAID 3—single writer, perfect alignment with the RAID stripe—are no longer necessary, as the write cache will align the data. RAID 3 is now more effective with multiple writing streams, smaller I/O sizes (such as 64 KB) and misaligned data.
RAID 3 is particularly effective with ATA drives, bringing their bandwidth performance up to Fibre Channel levels.

When to Use RAID 1
With the advent of 1+1 RAID 1/0 sets in Release 16, there is no good reason to use RAID 1. RAID 1/0 1+1 sets are expandable, whereas RAID 1 sets are not.


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