Featured Article

RAID 5 Data Recovery

HP PROLIANT 580 SERVER RAID 5:

I have an HP ProLiant 580 server on which I run a small client-based business. I have arranged the hard drives so that there are two 16gb hard drives running on RAID 1, and 5 hard disks running on RAID 5. I have more than a hundred users of my server as their point of entry for websites and mail systems. Most of these clients are business people who don’t want to wait while I solve server or array problems. The main difficulty I am having is that the server has lost one of the drives, and this means that it has lost a lot of the data which my clients store on the server. Many of them are still able to see their websites or mail drops, but they might not be able to see content, other pages, or even payment buttons. Only one of the drives is missing from the server, but it is certainly causing a lot of problems.

DELL POWEREDGE 6400 RAID 5:

I am using a Dell PowerEdge 6400 server which is running 2 SCSI drives to power the OS on my computer, plus another 6 SCSI drives which are arranged in a RAID 5 configuration and are being used for data storage. I have saved a lot of information to this drive, and it was working fine until just recently. The computer crashed, and it suddenly did an enormous data dump, including the blue screen of death, and now I cannot get the server to do anything. When I try to boot, I get an error message saying that No SCSI Chips Found, Firmware failed, Initialisation error 4001. I am not able to view the files on the RAID 5 array, and in fact the drives have been missing since that error occurred, and this means that I can’t find the information that I need, and which would allow me to save my data to another place and rebuild the server. I am really only concerned about the data on the drives, as I know that I can recover the disks by doing a rebuild.

RAID 5 Data Recovery

RAID 5 is unique because it’s able to rebuild itself if a single disk failure occurs. Although RAID 5 generally means a lower level of performance and overall capacity, it has become one of the most popular RAID configurations because of its ability to rebuild itself.

RAID 5 is typically ideal for situations where there is a high level of reading versus writing, such as within warehouses or on web servers. RAID 5 is also the go-to solution for many e-mail and news servers, Intranet servers and for private and home-based use. RAID 1, in general, offers better performance on writes, making RAID 5 a less than optimal solution for environments that require a high amount of writing.

Unlike RAID 1, RAID 5 does not create redundancy through the duplication of data. Instead, RAID 5 stores data through a process of striping across all of the drives found in an array. This technique of data storage is what makes RAID 5 a great option for reading, but not as beneficial for writing. With RAID 5, writing requires the re-caulculation of parity data.

RAID 5 does provide fault-tolerance, and although the capacity of the array is one less than the number of available drives because of the parity factor, it still offers more storage than RAID 1, which is at 50% of the available drives. In fact, the excellent level of fault tolerance provided by RAID 5, along with the fairly minimal loss of performance and efficiency are what make this well-balanced RAID option optimal for a wide variety of uses.

When a single drive of a RAID 5 array fails, the information can be regenerated from the information found on the parity, and if even a single drive failure is detected by the system, the whole RAID array will operate in a degraded mode. When a RAID 5 array notifies the user it is operating in degraded mode, the redundancy capabilities are no longer functioning and a rebuild process is a necessity in order to ensure the safety of all data is maintained. This is the most common reason users of RAID 5 arrays seek professional assistance. If a second array fails during the rebuild process, the entire array stops operating, rather than continuing to function in degraded mode.

There is a range of reasons that a RAID 5 array could fail, including bad sectors, corrupted files, missing partitions, overwritten files, firmware failure, drive failure and virus. When there is a potential problem experienced with the use of RAID 5, attempting to correct the problem on your own can lead to more problems and the potential for permanent loss of data. By trying to correct the problem without the help of a professional, parity data could be overwritten, which increases the difficulty level of recovery data.

If a problem begins to occur, the first step to take is to turn off the RAID server immediately. If the server continues to operate more data could be written to the array, which can result in data being overwritten. It’s also a good idea to record the events that led up to the RAID failure, and then immediately contact a data recovery professional company like ourselves that has 14 years experience in working with RAID 5 arrays.