Data Recovery on a 24 x 2TB disk RAID 6 Storage Array – What A Monster !!!
Have you ever wondered how organisations like the Ordanance Survey and applications like Google Earth get their data ?
Typically, these organisations will commission an aerial photography company to go up in a helicopter and take thousands of very high resolution photos of the area they want surveying. During the photography processes, the images are automatically tagged with GPS and meta data that allows each photo to be joined together to produce an overall photographic representation of the entire area. Using the meta information, these can then be further mapped and overlayed onto satellite images and other types of data.
As you’ll probably know if you own a decent digital camera, digital photographs create large files… for example, an 8 megapixel camera will create JPG images of roughly 1.4MB per picture. Aerial photographers will typically use a resolution of 18017 x 45801 – which creates a JPG of roughly 1.03GB in size – this is 1000 times larger than what an 8 megapixel camera produces !! – Now as you can imagine, the storage capacity necessary to hold thousands of these aerial images is immense, a 2TB disk will only hold approx 1600 images of this resolution.
We received an enquiry for data recovery from one such company. They had a storage array consisting of 24 x 2TB SATA HD’s containing hi-resolution aerial photographs of various parts of the UK landscape.
The RAID array was in a rack which was located underneath an air conditioning unit. Over a weekend the air conditioning unit developed a leak which spilt cooling fluid into the array taking 7 drives offline and the whole array down.
Once we were able to get data access restored to the drives we were able to work out the RAID configuration – which we found to be a 23 disk RAID 6 using Reed-Solomon error correction with 1 hot spare. This gave us a theoretical storage capacity of 42TB (21 x 2TB). The array was practically full with 41TB of data held on it – approximately 33,000 pictures, all of which we were able to recover successfully.