I came across this article today, and I think it is important for everyone to be aware of it.  It says that SSDs (solid-state drives), which are becoming increasingly popular for computer storage due to their fast access times and ability to withstand being dropped, “need consistent access to a power source in order for them to not lose data over time. There are a number of factors that influence the non-powered retention period that an SSD has before potential data loss. These factors include amount of use the drive has already experienced, the temperature of the storage environment, and the materials that comprise the memory chips in the drive.”  Keep that risk in mind if computers are powered down during a legal hold.  The article gives details about how long the drives are supposed to retain data while powered down.