S vs. HDD – choosing on the basis of data recoverability

12 February 2013 by Robert Winter

SSD chipSolid-state drives (SSD) continue to grow in popularity- especially as a solution for enterprise storage.  The benefits SSDs bring are impressive- particularly from a capacity and durability perspective- but they often eclipse any consideration regarding data loss and recovery.  For example, one of the great advantages that attract users to SSDs is that compared to hard drive disks (HDD) they are robust and less susceptible to shock and damage.  But even though data is well protected it doesn’t mean that data cannot be lost.

When considering which storage disk to choose, companies should be aware of how it can affect the ease of retrieving data when something wrong happens to it or the backup data. Understanding this requires a look at how data from a RAID (redundant array of independent disks) array is written to the media.

RAID is a technology that can store the same data on multiple disks to improve overall storage performance.  With solid state disks, the data is passed through various complex layers of controls. When the data reaches the individual drives, it goes via another controller called a wear-leveling controller. This controller decides which NAND chip and block inside that chip the data is electronically written. The location of the data on the NAND chips is always changing to prevent the NAND chips from wearing out.

With mechanical disks, the data is passed from the RAID controller to the individual disks and magnetically written in the drives as bits on a platter. The data can then be read from the platter by going back to the same location on the platter and by reading the magnetic orientation of the bit stored there. Knowing where the data is stored makes it far easier to recover it when a problem occurs, whereas with SSDs it’s hard to know where the data is located because the NAND chip is always changing.

SSD is a new technology and very few people have learned enough about it to expertly navigate through its RAID and the SSD layers and to successfully find data when there’s a failure.  Before choosing to use solid state over traditional hard disks, it is advisable to consider the impact of this technology in the event of data loss and subsequent data recovery.