SanDisk Extreme II SSD: For desktops and notebooks, a strong competitor to hard drives

Solid State Drives have been trying to play catch-up with hard disk electromechanical drives for almost a decade now.  Price per GB of storage as well as performance was a challenge -- but it looks as if solid state  flash technology  has bridged the gap -- and let's face it -- gone beyond what hard drives  can do in certain areas.

SanDisk's Extreme II SSD  is a case in point. Let me try and illustrate  how SSD has allowed memory designers to innovate and offer enhanced read-write efficiencies:  The bulk of its storage is achieved  using  Multi Level Cell (MLC) NAND flash memory  -- but every unit of the Extreme II ( which comes in three sizes: 120 GB, 240 GB and 480 GB)   includes just under 1 GB  of a non-volatile flash  cache which  the makers call nCache.    This  relatively tiny capacity  kicks in when the operating system  accesses the storage in small access blocks of around 4 KB -- which is quite often. Since the minimum block size of the  bulk NAND storage is  1 MB or more,  it is clearly  wasteful to allocate  such blocks. The nCache  accumulates such  small write cycles or segments at high speed and then consolidates them to larger MLC sections of the NAND Flash memory array.

In fact the Extreme II SSD  offers three  layers of storage:  the  NAND flash which is the bulk storage; the nCache -- and  a small cache of DDR DRAM --  approximately 1 MB of DRAM for 1GB of NAND. 

It is this multi layered storage technology which enables an SSD like  SanDisk's to go beyond what was achievable with electromechanical  hard drives  when it comes to  read write speeds of 500 MBPS and beyond.... great for high speed apps like photo  and video storage.

The Extreme II SSD costs  Rs 14,750, Rs 26,100 and  Rs 49,500  respectively for 120 GB, 240GB and 480 GB. It is backward compatible with  2.5 inch and 3.5 inch SATA  drives and  you can order  it with the necessary hardware to mount in notebooks or desktop PCs..... what one might call a 'solid' advance on PC  storage  options... even if a  bit  pricey when compared to hard disks

Anand Parthasarathy Nov 17 2013