Solid State Disks under the covers

SSDs are one of the hottest technologies in storage. Made with nonvolatile flash memory, they are unencumbered by seek time and rotational latencies. From a storage administrator’s perspective, they are simply a lot faster than disk drives. However, they are far from being a “bunch of memory chips” that act like a disk drive. The challenge with flash is that individual memory cells can wear out over time, particularly if they are used for low-latency transaction processing applications. To alleviate this challenge, SSD engineers design a number of safeguards, including metadata tracking for all cells and data, compressing data to use fewer cells, parity striping to protect against cell failures, wear-leveling to use cells uniformly, “garbage collecting“ to remove obsolete data, trimming to remove deleted data, and metering to indicate when the device will stop being usable. SSDs manage everything that needs to be managed internally. Users are advised not to use defrag or other utilities that reorganize data on SSDs. They won’t perform faster, but they will wear out faster.

Source of Information : Rethinking Enterprise Storage

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