Enterprise Flash Storage over the past 3 years has emerged as the leading type of storage for improving performance of applications and systems. Today Enterprise Flash Storage is being used in more applications and environments than ever before and is now the No 1 choice for tier 1 storage.
There are many types of Flash Storage to consider:
- All Flash Storage - The whole storage array is comprised of Flash
- Hybrid Flash - This uses a combination of Flash & Spinning Disk
- PCIe Flash - The Flash memory resides on a plugin PCIe card for your server or workstation
- Flash Cache - A few SSD drives are used as a cache for spinning disk
- Hybrid Drives - These are disk drives with a portion of flash which holds the most recently accessed files
Most of today's storage arrays use Non-volatile NAND flash memory which is supplied as SSD drives. There are three types of NAND and these are single-level cell (SLC), multi-level cell (MLC) or triple-level cell (TLC) technology. SLC stores one-bit-per cell, has longer endurance, but is significantly more costly to produce with higher capacities. MLC uses two bits per cell and TLC uses three bits per cell. These flash technologies have lower endurance, but hold larger capacities and can be produced at lower costs.
Flash stores data by use an electrical current to etch into Silicon a data bit and this causes Wear Levelling, whereby after so many programme erase / write cycles the Flash wears out and this could be 10,000, 100,00 or 1,000,000 writes depending on the type of Flash Storage used. Manufacturers overcome this problem in a number of ways by using sophisticated algorithms to work out how many times each cell has been used and then automatically re-map those blocks to another portion of Flash Storage.
There are three types of Wear Levelling:
- No Wear Levelling - Nothing is done with the cells and it wears out
- Dynamic Wear Levelling - Data is written evenly across the whole of the Flash
- Static Wear Levelling - Works out how many times a cell has been written and dynamically moves it.
If you want to know more about Flash Wear, please visit this site http://www.radio-electronics.com/info/data/semicond/memory/flash-wear-reliability-lifetime.php
The most common type of Enterprise Flash Storage uses SSD NAND today is MLC and this provides a high capacity and a far lower cost point than SLC. Whilst this does not have the highest Write Cycle the more sophisticated Enterprise Flash Storage vendors take this into consideration and employ Static Wear Levelling to ensure the maximum data lifecycle is attained and reliability remains intact.
Enterprise Flash Storage performance is a key criteria for replacing spinning disks, typically the fastest SSD drives can read/write at over 500MB/s with an IOP figure of 80,000. This is far better than spinning disk as Flash has no moving parts, whereas a disk drive needs to move an actuator arm with a read/write head across a spinning disk platter. Many of the applications which run today require Enterprise Flash Storage to deliver the high I/O required by businesses in order to save time and display the results instantaneously.