WeRecoverData.com - When to use RAID 3 and why?

Unlike RAID 7, RAID 3 is rarely used among all levels. According to some users, RAID 5 is superior in terms of performance, reliability and compatibility than RAID level 3 or 7.

Some disadvantages like:

• Transaction rate is equal to that of a single disk drive at best
• Fairly complex design of controller system
• Quite difficult and resource intensive to do as a ‘software’ RAID

In spite of its drawbacks, some specialised areas and benefits are unavoidable like:

• Single dedicated parity disk,
• High read and write data rate,
• No performance degradation in single drive failure,
• Similar performance in best or worst case

RAID 3 is combination of striping as well as parity and it stores all the parity information is individual parity disk. The result is an array that is certainly poor not only at random writes but also at random read. So it is clear that RAID 3 is not suitable or effective especially for transactional applications. But, on the contrary, RAID 3 shines in sequential read and write. In fact, it has been proved that RAID 3 is faster than RAID 5 in sequential read and write that works as efficiently as RAID 0 with the greater advantage of data protection. However, it reveals that RAID 3 is very good choice for larger files with mass amount of data and with the all workload. In applications that needs heavy updating and large file usage like graphics, video editing, video publishing, image editing, pre press, and streaming media, RAID 3 has most commonly applied.

Apart from this, a RAID 3 array has the capacity to bear the loss of single drive, and the most modern RAID 3 system supports hot spares as well as automatic rebuilding.

WeRecoverData.com - How to choose the right RAID level

Different RAID levels are for different kinds of requirements; it could be for organization, business or personal use. For example, for high performance reads and writes, it is better to avoid RAID 6 and use some smaller disk drives; on the other hand, to store mass amount of data where rebuild is possible RAID 5 and 6 is recommended to be the best option to application needs.

The following issues should be kept in mind before deciding which RAID will be the right choice:

1. One should avoid using disk drives that have higher chances of failure, so selecting RAID level 1 would be solution to avoid the performance impact as it has capacity to store data across multiple disks simultaneously.
2. Queries like for a RAID controller how many rebuild can happen concurrently, does a subsequent rebuild, after the replacement of failed drive, need to occur to relocate the additional disk in its original location should be considered; otherwise one is quite likely to become the victim of the problem like frequent drive failure which negatively affect the overall performance.
3. What RAID levels are supported, what is the granularity of RAID levels to function simultaneously and over what number and kinds of disk drive all are important information to know. Also check what flexibility you are provided with for tuning RAID as well as automatic RAID tuning by the storage system or controller for hands off operation.
4. Recognize how RAID implementation is optimised for sequential input/output application compared to random I/O over reads as well as writes. For database updates and processing, one needs his system to be optimised small random I/Os, but for larger sequential video or audio files one requires RAID system independent to support large sequential I/O operation. For larger IOPs, then look for IOPs per second to go down while MB/sec goes up.
5. User should have knowledge about what should be done to alleviate performance impact on both write and read level and during rebuilding process for duel based RAID implementation.
6. Keeping requirement of various applications in mind, one needs to know what level of service is needed and why to use RAID to meet up daily challenges or odds. Users should also know the right RAID level to support sequential or random small or large I/O processing, reads compared to writes.
7. If a RAID offload or accelerator engine is used, one has to estimate what output is expected, and after using, what performance was actually achieved.
8. A common misconception is that more cache is always a better option and also that higher cache utilization means improved performance. The ground reality is, only a few systems need more cache to offset in order to move data quickly to or from hard disk. It is always advisable to go for a cache of high performance and make sure it is utilized effectively.

WeRecoverData.com - How to replace a failed drive in the array

Identifying which drive has failed before replacing is a crucial task; one wrong step or negligence may corrupt the entire array. It is strongly recommended to double check the whole work in order to trace the affected drive before attempting to change or even touch them.

While installing drive in the array, one should note down the serial number of the drive assigned to every Operating System identifier and keep all the valuable information up to date at the time of drive replacement. Further, the system needs to be rebooted; nothing to worry about, one can go ahead, reboot and check the controller’s RAID BIOS. The BIOS will recognize the serial number of the drive and give a clue which drive needs to be replaced. The serial number of the failed drive will simplify the process to further confirm the serial number of all drives in the array. One is required to be very careful about it as the original drive has the similar serial numbers, for one can recheck the entire procedures in order to ensure the right drive has been identified.

A number of enclosure vendors have warning LEDs on their racks, especially in hot swap system. An orange or red light will help to distinguish the failed drive. Moreover, some vendor management software can identify the failed drive by its location in the tray and some error-prone identification system will even draw the whole diagram that will help making out the exact drive rack or tray. After all these warnings still one can possibly make mistake, so professional help should be taken in this case.