SSDs
SSDs are great. Their price has been lowered enormously over the last 10 years, and all evidence suggests that it will continue to do so. They have the ability to offer access times several orders of magnitude lower than rotating disks and consume less power.
One important concept to understand about SSDs is that, although their read and write latencies are typically measured in tens of microseconds, to overwrite existing data in a flash block, requires the entire flash block to be erased before the write can happen. A typical flash block size in an SSD may be 128k, and even a 4 KB write I/O would require the entire block to be read, erased, and then the existing data and new I/O to be finally written. The erase operation can take several ...
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