LSI 9265-8i 6Gbps MegaRAID Card RAID 5 Tested! – RAID 0/5 Explained

Lets do a quick primer on the differences between RAID 0 and RAID 5.

RAID 0

RAID Level 0

RAID 0 is commonly referred to as ‘striping’ or a ‘striped array’ because its approach is striping data across multiple disks without any redundant information. An example of this in simple terms would be similar to taking a sentence, and placing each word on a separate disk.

For instance : “A man walked across the street”.  In a single disk scenario, all six words would be on the one disk. When you asked for the sentence to be repeated back the disk would access them and give them to you one at a time.

If you were to place the sentence on six disks, one word on each disk, when you went to access that information you would get all six words back, simultaneously. This in effect is the workings of RAID 0. By utilizing separate disks to reply simultaneously you gain a speed advantage.

Striping is the fastest type of RAID, but unfortunately there is absolutely no safety net. If you lose one disk, the entire set of drives is unusable. There is Zero Fault Tolerance. Also, a consideration is that the more devices that you add, the more your probability of failure goes up.

RAID 5

RAID Level 5

RAID 5 is commonly referred to as “Striping with Parity” because its approach is similar to RAID 0 in that it stripes data across several drives. However, it also adds a layer of Parity to the stripe. If a drive in the array fails, remaining data on the other drives can be combined with the parity data to reconstruct the missing data.  So, RAID 5 is Fault Tolerant. You can lose a disk, and the array will continue to function.

Unfortunately, the write performance of RAID 5 can be poor. This in part is where caching can come into play to ‘smooth’ out the writes. There is also the penalty of losing some of your capacity in a RAID 5 setup. You will lose some disk capacity to the parity information that must be stored. For all of the drawbacks of RAID 5, it is still very widely used. The speed of data retrieval is still very good, yet you also have a safety net. For the sake of data redundancy and security, RAID 5 is much more reliable than RAID 0.

LINKED INDEX

Introduction ~ Test Bench & Protocol ~ Card Settings

RAID 5 Explained ~ Initial Tests ~ AS SSD

HDTune ~ Win 7 & AIDA ~ IOMeter 08

Vantage and Final Thoughts

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