Storage Tiering

This is another topic I’ve been reading a lot about lately.  Storage tiering uses expensive faster access drives for frequently used data and slower less expensive  access drives for older archive type data. 

Typical fastest level tiers in a data center will use an optically connected fiber channel disk array, followed by Small Computer System Interface (SCSI) attached drives, followed by Serial Advanced Technology Attachment (SATA) drives followed sometime even by tape drives. Tape drives – I know – but yes they are still used - typically to take content completely offline and store.

Mechanical drives have been historically used for the fastest tier but as prices drop and operating systems include better support , we’re seeing a lot of much faster solid state memory devices (solid-state drives (SSDs) and I/O accelerator cards (sometimes referred to as solid-state accelerators [SSAs]) used for the faster level  tiers now.

What’s the difference between a SSD and an SSA? They both basically do the same thing – the only difference is the data interface. 

• SSD’s look like a mechanical hard drive and the server operating system uses standard BIOS calls to access. 
• SSA’s are a little different and use a PCI Express (PCIe) interface. The operating system must use a unique set of software drivers specific to the SSA device being used. 

Because SSA’s use drivers that have been tuned specific to the device, they tend to be a little faster. Both SSD and SSA devices can work together on the same server.