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slecting the RAID Type is based on the needed function and purpose, like if you need more high availability so mirror is your best choice (RAID1) etc... but any way If you really don't know what RAID level to choose, go with RAID50 if capacity is more important than performance (unless you're talking mostly sequential reads, in which case RAID50 is awesome) or RAID10 if both random and sequential read/write performance trumps capacity. If data protection is your primary concern, RAID6/60 should be at the top of your list.
Basm Alah Alrahman Alrahim
Striping - Mirroing - Parity
If you have a file (e.g video file ) with big size and you want to edit faster , note this file is saved at the hard disk and when you make editing you make it at ram then save it at this hard , so if you divide this file into two hards ( i.e striping or RAID0 ) it will be transfeard faster , with more division ( more hards ) that give you more speed for transfare
If you make a copy of one file into two hards or more (i.e mean you are mirroring or RAID1) so if one of the hards failed you will find another copy of it
If you get three hards and make two copy of one file at two hards and make the theard hard for some thing to check or test between the two copies if thay are the same or test if thay are wronge or right ( all the time ) that mean parity or RAID2 ( RAID5 is another way to RAID2 but with some thing called distributed Parity )
Selecting the RAID level is a tricky job. Following factors are needed to be kept in mind while selection of RAID.1-Redundancy2-Capacity3-Read I/O4-Write I/O5- Spare drives6-Maximum and Minimum No of drives etc...
as brief as possible.. my criteria is based on data access and redundnacy
on small scale, depending on the number of drives,Fast Data Access / Read-Write Speeds , you usually have two choices ,
either it's RAID0 that works on Data Striping Method, no redundancy, one disk fails and you lost everything
or Higher Levels of RAID that uses both Striping and Mirroring at the same time, gaining both Redundancy and Fast Data Access, such as RAID10,50 and60.
The most Common Practice for Small Scale Servers, they use RAID5, it has a moderate Data Access Speed and reliability compared to other types of RAID
if we are speaking of Storage, RAID5 is the least RAID level you can think of but still depends on the storage type, usually customers whom are concerned with Data integrity , usually uses RAID60, but you need alot of Disks for such deployment so as not to loose alot in reserved space.
you need to provide a typical scenario for a best practice recommendation
RAID level considerations
When choosing a RAID level for a new array, there are a number of important points that you need to take into consideration, including:
Application performance needs: Not every application is created equal. Some applications are light on I/O needs, while others thrash the storage system all day long. Make sure you choose a RAID level that matches the workload.
Capacity needs: Different RAID levels all result in different amounts of net usable space remaining after accounting for RAID overhead. If capacity is your primary driver that will affect your choice of RAID.
Cost: Performance costs money, and capacity costs money -- achieving the necessary balance between cost and performance is your job. Choosing the right RAID level can play a big part in achieving this balance.
Availability needs: Every business is different. Perhaps your business is willing to pay a little more to ensure less downtime than another business. In these cases, you need to pick a RAID level that matches the system's availability needs demanded by your organization
Please see below the best RAID in each points of consideration:
Application performance
* RAID0. From a performance perspective, RAID0 beats the rest since there is no RAID overhead, and the disk system is able to aggregate all of the disks into a single, high performance storage pool.
* RAID1/10. In most cases, RAID10 provides excellent performance since data can be read from multiple disks at the same time, suffering a little only when the workload calls for a whole lot of small sequential writes. For general raw performance for pretty much any kind of workload, RAID1 and10 are excellent choices. RAID1 by itself is a two disk system that doesn't get a huge performance boost, but it wouldn't likely be used in a large array, anyway.
Capacity
* RAID0. Since no parity information is stored and there is no mirroring, RAID0 provides excellent capacity. You get full use of all of the disks in the array --100% utilization.
RAID1/10. With RAID1/10, you take a full50% capacity hit due to the need to retain a mirrored copy of the data. RAID1/10 carries the largest capacity penalty, but this is often offset by its very good read/write
Performance
* RAID5/50. One reason RAID5 remains so popular is because of its capacity overhead, which results in the loss of only one disk worth of capacity. Under RAID5/50, you will lose up to33% of total raw capacity (three disk RAID5 configuration), depending on how you create your volumes.
Cost
* RAID0. From a capacity and a performance standpoint, RAID0 carries by far the lowest price tag. With no RAID overhead and maximized performance, the $/TB or $/IOPS metrics are fantastic under RAID0.
* RAID5/50. RAID5/50 has become an almost de facto standard when one needs to add RAID and doesn't really care about the characteristics. All RAID controllers support RAID5, and the RAID5 capacity overhead isn't too bad, especially as more disks are added to the array. From a performance perspective, you do lose a lot of IOPS on write workloads, making RAID5 a bit more expensive than RAID0,1, and10 when it comes to supporting write workloads.
Availability
* RAID1/10. RAID1/10 - mirroring - is a highly available configuration. All data are written to two disks in the array, so you can lose multiple disks -- as long as you lose the "right" ones -- and remain functional on a single copy of the data.
* RAID6/60. RAID6/60 provide very high levels of availability since you can lose two disks in each RAID6 array and remain functional.
If you really don't know what RAID level to choose, go with RAID50 if capacity is more important than performance (unless you're talking mostly sequential reads, in which case RAID50 is awesome) or RAID10 if both random and sequential read/write performance trumps capacity. If data protection is your primary concern, RAID6/60 should be at the top of your list.
Choosing a RAID Level is basically a tradeoff between, Performance, Reliability & Capacity.
RAID0 --> Provides Best performance, but no fault tolerance.RAID1 --> Good Read performance with100% fault tolerance, but high disk overhead.RAID2 --> Highly Reliable, Error fixing happens spontenously, But requires an entire disk for correction.RAID3 --> High Data Transfer Rates, but slower performance RAID4 --> Overlaped IO for Reading, but not for WritingRAID5 --> Better Read Performance, But difficult to overcome disk failure.
