What is special about enterprise-class SSD storage? Not only focus on IOPS, but also pay more attention to QoS.

Source:   Editor: admin Update Time :2019-07-05

What is special about enterprise-class SSD storage? Not only focus on IOPS, but also pay more attention to QoS.

One of the big selling points of NVMe SSDs is the superb IOPS parameter, which is the number of reading and writing operations that the hard disk can perform per second, but this is only a surface. Enterprise-class SSDs have a very high IOPS random read and write performance, but also have some more important capabilities to really play its power.


SSDs, like mechanical hard drives, have some cases where they can only work "single-threaded". For example, when a die of a NAND flash is writing, it cannot respond to a read request at the same time. In Toshiba's BiCS3 flash memory, a flash die has a capacity of 256Gb or 512Gb. Each die is the smallest independent unit in the flash that executes commands or returns its state.


Ordinary applications focus on average IOPS, enterprise-level pays more attention to QoS
The performance of mechanical hard disk is relatively easy to expect, while the solid-state hard disk with NAND flash memory is more powerful, but it may be read in flash memory because the writing speed is slower than reading and needs to be erased before writing.
The performance of mechanical hard disk is relatively easy to expect, but solid-state drives that run on NAND flash, while more powerful, can cause some unusual extra latency in flash reads due to features such as slower write times than reads and needing to be erased before writing. There are some unusual extra delays in the process. The following picture shows Joe Dedrick, vice president and general manager of Toshiba Storage's KumoScale Accerelated Storage Group, introducing the abnormal read latency of flash memory when interviewed by the Swiss Storage Home website.

There are a lot of judgment loop structures in the application, and additional storage delays will affect the program execution efficiency. For traditional enterprise applications, you can rely on average latency to assess operational efficiency.

Under the cloud architecture, the efficiency of distributed cloud applications depends on the slowest link in the entire architecture, which means higher requirements for storage performance consistency. The effect of a small probability of an abnormal flash read latency will be magnified many times in the application.

Toshiba has made a lot of efforts to meet the stringent demands of enterprise-class cloud architecture applications for consistent storage performance.

KumoScale Accelerated Storage
KumoScale implements read-write separation from the host side, reducing the impact of write operations on flash read latency. To put it simply, Toshiba's KumoScale Accelerated Storage technology divides the SSD storage pool into two groups, one of which can handle simultaneous write requests while another group reads, avoiding a flash die in the SSD because of reading and writing cannot be made at the same time and create additional access delays.

Relatively speaking, the use of home SSDs is much smaller, so there is usually no optimization for QoS. In fact, even the original entry-level SATA solid state is enough to support 99% of home applications. General online video and gaming entertainment needs are fully met.

In terms of flash durability, Toshiba uses the same BiCS 3D stacked flash memory as the enterprise-class SSD products on the entry-level TR200, except that their erase and write cycles are slightly different: the enterprise-class eTLC flash erasing and writing life is 7000 times to 10,000 times, the original quality TLC erasing and writing life of the TR200 is about 3,000 times.

As for non-original SSDs, it is possible to reduce the cost by using an ordinary physical TLC of 1000 erasing and writing life. The flash memory used by USB flash drives and memory cards is usually a life of 300 times or less.


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