These days, if you ask any system administrator something like “what should I do to boost the performance of my I/O-hungry applications?” probably, the most common answer will be “go and get some SSDs”. No wonder, as flash memory becomes more and more affordable while delivering benefits that in the majority of cases outweigh Hard Disk Drives, such as significantly higher performance and better reliability. However, when choosing SSDs, you have to keep a few things in mind since performance, durability, and price vary from model to model.
So what should you ask yourself or a vendor when choosing SSDs?
How much IOPS can it squeeze?
The number one question on my list will be performed. The number of Input/Output operations per second (IOPS) shows how often an SSD can perform a data transfer every second. However, the trick is that various devices have different read/write characteristics. Therefore, check your system’s workload. Is it write- or read-intensive? Only having the full knowledge of your environment can you choose a proper SSD that will really provide your applications with higher performance. In other cases, you risk spending money on flash storage without fully experiencing its benefits or achieving its goods but for a price much higher than it could actually be.
How long will it last?
The next thing I’d recommend taking into account is SSD’s durability, longevity, endurance or simply stamina. The matter is, that the stamina of flash memory cells is defined by the number of times it can be erased and re-written (program-erase cycles). There are two measurements to look at: number of drive writes per day (DWPD) and the total amount of terabytes that can be written (TBW) to the media during its whole lifespan. What’s the difference? Well, DWPD depends on the drive size whereas TBW does not. For example, you have an SSD with 100GB which can take 1,000 TB of writes for its warranty period, say 5 years. So: 1,000TB/ (100GB x 365 days x 5 years) = 5.5 DWPD. Now, let’s take a 200GB SSD: 1,000/ (200GB x 365 days x 5 years) = 2.7 DWPD. As we can see, the 400 GB SSD, in fact, will have lower stamina than the drive with lower capacity. Sure, if workloads are equal for both devices, TBW can be taken into account. However, a larger drive will probably serve storage for more workloads, thus it will have just a half endurance of the smaller one. If you ask me, I’d recommend keeping your eye on DWPD. The more the better.
How much does it cost?
It’s not all that simple here. The price of SSD is not just a calculation of $/GB. Actually, you have to take much more factors into account. First of all, the two major indicators are $/IOPS and $/GB. Also, in some cases, it may be more cost efficient to purchase a less expensive SSD with shorter durability and then replace it with the new one (indeed prices for SSDs are slowly getting lower) than paying more for a longer lasting enterprise-grade device. Also, it’s worth mentioning that you can take advantage of data optimization technologies such as data deduplication and compression. This will help you in reducing the final solution cost as you can fit in more data into the same physical capacity.
As you can see, the price is not the only factor in choosing an SSD. You really need to know what you’re paying for, and it’s not just IOPS or storage size itself. SSD’s read/write characteristics should match those of your workloads or you’ll be paying for nothing. Also take a look at its longevity, especially DWPD, it’s a more precise criterion than TBW. Hope this article was useful, and perhaps, it comes in handy when you’ll be shopping for SSDs one day.