Editing RAM drive (section)

== Performance ==
The performance of a RAM drive is generally [[order of magnitude|orders of magnitude]] faster than other forms of digital storage, such as [[SSD]], [[tape drive|tape]], [[optical disk drive|optical]], [[hard disk]], and [[Floppy disk|floppy]] drives.<ref>{{cite web |url=http://fiehnlab.ucdavis.edu/downloads/staff/kind/Collector/Benchmark/RamDisk/ramdisk-benchmarks.pdf |title=RAMDISK Benchmarks |publisher=University of California |author=Kind, Tobias |access-date=2019-03-21}}</ref>  This performance gain is due to multiple factors, including access time, [[throughput|maximum throughput]], and [[file system]] characteristics.

File access time is greatly reduced since a RAM drive is [[solid state (electronics)|solid state]] (no moving parts).  A physical hard drive, [[Optical disc|optical]] (e.g, [[CD-ROM]], [[DVD]], and [[Blu-ray]]) or other media (e.g. [[Bubble memory|magnetic bubble]], [[Delay-line memory|acoustic storage]], [[Magnetic tape data storage|magnetic tape]]) must move the information to a particular position before reading or writing can occur.  RAM drives can access data with only the address, eliminating this [[Latency (engineering)|latency]].

Second, the [[throughput|maximum throughput]] of a RAM drive is limited by the speed of the RAM, the [[Bus (computing)|data bus]], and the [[central processing unit|CPU]] of the computer.  Other forms of storage media are further limited by the speed of the storage bus, such as [[Integrated Drive Electronics|IDE]] (PATA), [[SATA]], [[USB]] or [[FireWire]].  Compounding this limitation is the speed of the actual mechanics of the drive motors, heads, or eyes.

Third, the [[file system]] in use, such as [[NTFS]], [[Hierarchical File System (Apple)|HFS]], [[Unix File System|UFS]], ext2, etc., uses extra accesses, reads and writes to the drive, which although small, can add up quickly, especially in the event of many small files vs. few larger files (temporary internet folders, web caches, etc.).

Because the storage is in RAM, it is [[volatile memory]], which means it will be lost in the event of power loss, whether intentional (computer reboot or shutdown) or accidental (power failure or system crash).  This is, in general, a weakness (the data must periodically be backed up to a persistent-storage medium to avoid loss), but is sometimes desirable: for example, when working with a decrypted copy of an [[encrypted]] file, or using the RAM drive to store the system's [[temporary file]]s.

In many cases, the data stored on the RAM drive is created from data permanently stored elsewhere, for [[Cache (computing)|faster access]], and is re-created on the RAM drive when the system reboots.

Apart from the risk of data loss, the major limitation of RAM drives is capacity, which is constrained by the amount of installed RAM. Multi-terabyte SSD storage has become common, but RAM is still measured in gigabytes.

RAM drives use normal system memory as if it were a partition on a physical hard drive rather than accessing the data bus normally used for secondary storage. Though RAM drives can often be supported directly in the operating system via special mechanisms in the OS [[kernel (operating system)|kernel]], it is generally simpler to access a RAM drive through a [[virtual device]] driver. This makes the non-disk nature of RAM drives invisible to both the OS and applications.

Usually no battery backup is needed due to the temporary nature of the information stored in the RAM drive, but an [[uninterruptible power supply]] can keep the system running during a short power outage.

Some RAM drives use a compressed file system such as [[cramfs]] to allow compressed data to be accessed on the fly, without decompressing it first. This is convenient because RAM drives are often small due to the higher price per byte than conventional hard drive storage.