Speed ​​orientation: an overview of the "elite" corporate SSD and HDD

Building a corporate storage system is not an easy task, and to solve it, first of all, you need to decide what data you plan to store and, more importantly, how fast the access should be. Best of all, the separation of corporate data warehouses by tasks is illustrated by such a pyramid.

Today we will talk about the elite of storage systems - hard drives and solid-state drives that serve the most demanding systems, where the speed of obtaining information (of course, with the highest reliability) is one of the most important factors. This post is the first in a series of review materials on HGST products. In the near future we will talk about other corporate HDD companies, as well as hard drives for regular users.

Dollars, gigabytes and watts
Choosing a hard drive for corporate storage begins with defining tasks for that system itself. Everything is simple: the faster this data needs to be given, the more productive each element of the system should be. The simplest system is the one in which you need to store a lot of data, and the speed of their retrieval is not that important. For this task, the most capacious 4-terabyte hard drive HGST, which we have already written, is perfect. Next, in order of increasing data storage bandwidth requirements, are web servers and cloud systems. Well, at the top - data analysis systems, as well as, for example, services for conducting banking transactions. Here they require everything to the maximum: the speed of reading data, the number of IOPS per second, and the minimum access time.

The obvious solution to all performance problems are solid state drives. Indeed, even the fastest HDDs lag behind the SSD in speed, well, not by an order of magnitude, but significantly. But there are also problems with SSDs. First, the price exceeding the cost of fast HDD, and significantly. Secondly, smaller volumes (HGST has a maximum of 400 GB in SSD versus 1.2 terabytes in HDD 10K RPM). Thirdly - a small resource of memory cells, although this is partly solved (of course, at extra charge!) By using more resistant flash modules of the Single-Level Cell type.
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Returning to the subtitle: in addition to the data transfer rate determined by a specific task, there are three main criteria for choosing a drive: initial investment (how much it costs), volume (how many gigabytes we get for the money) and power consumption and the total cost of ownership (how much we will pay each month for maintaining our storage system in working condition). The combination of these parameters leads us to the conclusion that although in the long term SSD will replace hard disks in the most heavily loaded tasks, so far there is an approximate parity between these types of drives in this area.

And now, more about the models.

15K RPM
Most recently, HDD manufacturers have experimented with high-speed hard drives, even in the consumer market: before the advent of affordable SSDs, this was the only way to dramatically speed up a powerful home computer. Now such models remain only in the corporate series, incorporating the most advanced technology for storing data on magnetic media.
An example of such a drive is a 3.5-inch HGST Ultrastar C15K600 . Available in versions with a capacity of 300, 450 and 600 gigabytes, it provides high speed data exchange (up to 198 megabytes per second), and supports SAS and Fiber Channel Arbitrated Loop (FCAL) interfaces. All modifications are equipped with a capacious buffer for 64MB data.

A slightly less high-speed, but more economical model from the high-speed series is the 2.5-inch Ultrastar C15K147 . Typical power consumption under load for this 147-gigabyte model is 7.3 watts, versus 16.6 watts for the older model C15K600. This is comparable to the indicators of HGST SSD (from 5 W). Both models, by the way, are provided with a five-year warranty and have an MBTF of 1.6 million hours (compared to 2 million for corporate SSDs and slower Ultrastar 7200 RPM HDDs).

Corporate SSD
As you know, the main problem of SSD is a relatively small number of rewriting cycles that can be sustained by SSD cells. There are technologies that allow this limitation to be circumvented, but in conditions of high-loaded corporate storage, where SSDs are used "to the full" all day and night, this factor cannot be ignored. Therefore, HGST produces two main modifications of solid-state drives, different technology - available as a relatively inexpensive Multi-Level Cell model ( SSD400M ), and more durable Single-Level Cell ( SSD400S with flash memory modules made using 34 nm technology and SSD400S.B with more modern 25 nanometer technology). In all options, drives are available in volumes of 100, 200 and 400 GB.

It is noteworthy that HGST drives provide better numbers of rewriting cycles than the industry average. For MLC drives, this is 30,000 cycles (versus standard 10,000), for SLC it is 200,000 cycles (versus 100,000). Typical power consumption for the SSD400M model is 6.5 watts, for the SLC versions - 5.5 watts. Data exchange rates are also “above the market”. For SLC models, the linear read and write speed is 516 and 458 megabytes per second, respectively. The typical number of I / O operations per second (IOPS) is 42,000 for reading and 21,000 for recording (slightly higher for MLC versions), which is almost a hundred times higher than the fastest HDDs.
In the next article we will talk about corporate HDD with a spindle speed of 10 thousand revolutions per minute, providing comparable to SSD power consumption indicators - 5.8 watts for the most capacious drive of 1.2 terabytes.