For customers considering our dedicated server options, one of the questions you'll need to answer about your server configuration is whether to utilize a RAID disk configuration or not.  The following article will provide you information to help you make that decision.

For our shared hosting customers, all of our shared server hardware utilizes a RAID disk configuration as a measure to help ensure maximum server uptime.  (a fact that might influence our dedicated server customers decisions on RAID!)

An Overview Of RAID

RAID stands for Redundant Array of Independent Disks.  The purpose of RAID is to provide redundancy for hard drives in the event that a hard drive is lost due to mechanical failure.  Hard drives are the most susceptible component in a server to fail, just by the nature of it's design.

RAID solves this problem by copying data from one drive to another in real time.  For every bit that is written to one drive, it's also written to it's "mirror" counterpart.  So, in the event that one drive is lost, the other drive is available to continue reading and writing data without any interruption to the server.

There are many types of RAID.   For the most part 3Essentials uses RAID 1 "mirror" and RAID 5 "striping with parity".

RAID 1 consists of TWO hard drives.  Data from one drive is copied in real time to the other hard drive.  In the event that one of the drives is lost, the other drive available to continue reading and writing data without any interruption to the server.

RAID 5 consists of THREE or more hard drives.  RAID 5 requires a minimum of at least THREE (3) drives.  Redundancy is provided by "striping the parity" across all drives.  This means that any one drive contains the "redundant" information.  If one drive is lost, the other two drives continue reading and writing data without any interruption to the server.

Do I Need RAID ?

The question you must ask yourself is, "can I risk losing my data ?".  If the answer is yes, then you do not need RAID.  There are many other components in a server that can fail that will cause downtime while the failed part is repaired.  CPU, Memory, Power Supplies...etc.  The failure of any of these parts does not result in loss of data.  RAID is not a guarantee that data will not be lost, but it dramatically reduces the chance of data loss due to a hard drive failure.  Again, hard drive failures are the most common failure in any server or computer.

What if a RAID drive fails ?

3Essentials will replace the drive with another drive.  Depending on the type of dedicated server plan you purchase, we may or may not have to shut the server down to replace the drive.

What if a drive fails and I don't have RAID ?

In the event your server has non-RAID drives, 3Essentials will replace the bad drive.  If your Operating System and/or applications reside on that drive then the server will be down and offline while the OS is re-installed and any applications are re-installed.  3Essentials does not provide any "guaranteed" times as to how long a re-build might take.

Is there any cost to me when a drive fails ?

For dedicated servers plans there are no costs involved for replacement of a drive failure.

A note about hard drive failures...

A study by Carnegie Mellon University, where the researchers took roughly 100,000 hard drives from a variety of manufacturers, concluded that hard drive manufacturers were exaggerating their mean-time before failure (MTBF) ratings on hard drives – failure rates were, on average, 15 times the rated MTBFs. The drives were tested in various operating conditions, including real world scenarios. Researchers found that drive operating temperatures had little to no effect on failure rates: a cool hard drive survived no longer than one running hot. The types of drives used in the study ranged from Serial ATA drives, SCSI and even high-end fiber-channel (FC) drives. Carnegie researchers found that high-end drives did not outlast their mainstream counterparts: “In our data sets, the replacement rates of SATA disks are not worse than the replacement rates of SCSI or FC disks. This may indicate that disk-independent factors, such as operating conditions, usage and environmental factors affect replacement rates more than component specific factors.”

The study also found that the number one cause of drive failures was age. Drives tended to start showing signs of failure after roughly five to seven years of service, after which there was a significant increase in average failure rates (AFR). The failure rates of drives that were in their first year of service or shorter was just as high as those after the seven year mark. The average replacement rate of drives ranged from 2-13% annually, indicating that there is a need for manufacturers to re-evaluate the way a MTBF rating is generated. Worst of all, these rates were for drives with MTBF ratings between 1 million and 1.5 million hours. Carnegie researchers concluded that backup measures are a necessity with critically important data, no matter what kind of hard drive is being used.