Solid State SAS, Value SAS and SATA Drives: Fast storage medium for random IO
10K & 15K SAS Hard Drives: Performance and availability for performance optimized applications
7.2K SAS & SATA Hard Drives: High capacity and exceptional $/GB for capacity optimized applications
Entry Drives: Least expensive drives used in applications where low usage and limited total number of drives are applicable. Due to restrictions on use, these drives are available in a small number of systems and configurations.
HDD RecommendationsHard Disk Drives for Dell Enterprise server and storage products are available in several different types, including Mission Critical (10K & 15K) Performance Optimized, Business Critical (7.2K) Capacity Optimized.
Generally speaking, the Mission Critical (MC) or Performance Optimized drives (10K and 15K SAS) are used in those application requiring the highest reliability and performance and are only available in the 2.5” small form factor. Business Critical (BC) or Capacity Optimized drives (7.2K Nearline SAS and SATA) may provide much higher capacities, but lower reliability and performance when compared to Mission Critical. They are available in both 2.5” small form factor and 3.5” large form factor. There is a fundamental transition occurring in the HDD industry. The standard size of a basic unit of data (a sector on the drive) is changing from 512 bytes to 4K bytes. Fortunately there are ways to maintain the 512 byte sector size, so that both are available into the future. Below is information on that addition and what a user should consider:
- Beginning in late 2009, accelerating in 2010, and hitting mainstream in 2011 for client-based HDDs, hard drive companies began migrating away from the legacy sector size of 512 bytes to a larger, more efficient sector size of 4,096 bytes, generally referred to as 4K sectors, and now referenced as Advanced Format by IDEMA (The International Disk Drive Equipment and Materials Association). Enterprise HDDs are also moving to embrace this format, but will be slower to adopt. The first Advanced Format enterprise HDD became available in 2012, with a limited set in 2013 and a more general distribution in 2014 and beyond.
- Customers have been using applications and operating systems / file systems built on 512 bytes (512n) for decades. This move to 4K byte sector size will impact those software stacks and will result in additional validation work as well as possible structural changes to software as the transition is made. New, higher capacity drives will need to be created in this 4K format. Recognizing that customers may be reluctant to make a change like this quickly, an emulation model of these drives has been created – the drive is built from 4K technology, but allows for 512 byte addressing and transfer at the interface. These drives are known as 512e.
- Below is a table describing these concepts:
|Format type||Bytes per sector value||Bytes per physical sector value|
- There are many aspects of modern computing systems that continue to assume that sectors are always 512 bytes. The Dell HDD offering contains 512n drives, 512e drives, and drives in the 4Kn format. The 512n format is available for customers interested in maintaining the same drive type they have used over time. The 512e drives provide a 512 byte sector size for those capacities not available in 512n. The 4Kn formatted drives are for those customers interested in adopting the latest, highest capacity HDDs and for those getting prepared for the future direction of the HDD industry. Note that 512 byte/sector addressing will continue as a recognized and supported format for many years into the future. The share of drives formatted as 4Kn could continue to remain small and the newest, highest capacity HDDs now and on the roadmap will also be available in 512e sector format.