Paisit Blog

We are hearing the story of Solid State Drive more and more. It's the flash memory that based on NAND gate (developed by Toshiba since 1989). Most of implementation today is in consumer electronic (thumb drive, MP3 player,digital camera card,etc). We can name it "Consumer Flash SSD". Since cost of  NAND gate drop very quick due to economic of scale, we start to see "Enterprise Flash SSD" in data storage system since last year. 

In the computer market, SSD is no doubt that potentially can reduce gap between speed of CPU/memory and HDD. Latency of HDD is in mili seconds v.s. DRAM is in nano seconds. Really Big gap there, that's why we have cache in storage as buffer to relief this gap. However, cache memory in storage is not cheap to acquire. So it's very exciting to see how SSD can play role in this area.

Although cost of SSD drop heavily in the last few years. But it still can not match up to HDD price($/GB) as well as its size (32GB to a few hundred GB). It's not really possible to replace HDD with SSD today due to mentioned reason. That lead to use concept of tier storage with SSD in the picture. It mean we will place some data on different tier based on several requirements i.e., latency, operation expense (OPEX), capital expense (CAPEX), retention time and so on

SSD is not only solve the storage performance with excellent response time but also in term of Eco-friendly. Without any mechanical movement, it reduce power consumption substantially as well as its weight compare to HDD, hence, less cost to build raise floor that can support heavyweight giant like disk array. 

Implementation of SSD

Due to SSD is faster than FC disk (usually classified as tier1), so the storage industry seem (by default) to define SSD in as tier 0. With solid-state storage at a higher cost vs. high-end disk drives, users are selectively deploying solid-state storage to increase app performance. As a general rule of thumb, solid-state storage is used in environments where disk drives are the limiting factor. Mission-critical apps like transaction processing and database systems linked directly to a firm's success (SLA) are prime examples of where solid-state storage is used today. Logs file area of  databases or whole database are other candidates for solid-state storage.

There are number of ways to implement SSD in the computing environment. for example, 

(1) Replace HDD with SSD in existing array. This may be seen as simplest way, however, since SSD performance is so fast which the current back-end of disk array may not be able to work with it effectively (back-pane too slow). User should add a few SSD and choose only volume they think it's a must to leverage SSD and leave other slots for HDD (tier storage within same array). 

(2) Put SSD as separate array, you may name it Flash Array or whatever (look like huge big iPOD). The whole array is all SSD. This is a very clean way of adding a Tier 0 , as it eliminates the need to tamper with disk-based arrays. 

(3) Replace SSD in server internal drive. This is another candidates. Since back-pane of server seem to be very fast and some server now have a lot of drive (48 HDD inside Sun X4540 server). Adding SSD in can improve performance while still comprising on back-pane performance.

There is a possibility that in the next two to three years, we can see Tier 0 solid-state storage become a standard array option and it will come at a bit premium price and users will deploy it selectively. In the longer term, as pricing for NAND flash decreases, SSD will begin to replace high-end disk drives due to power consumption, footprint, cost, performance, reliability.