Find out how SSDs stack up to hard disk drives and how they can benefit your data center.
The storage industry is at a major crossroad. Hard drives have been eclipsed in many areas by solid-state drives and the effects of this now mature technology are rippling across the storage industry, changing everything from software to appliance configurations.
A few urban myths have grown up during the rapid evolution of SSD storage. Some of these cast doubt on durability or pricing, and even the performance benefits of drives that run hundreds of times faster than hard drives. These misconceptions have slowed SSD adoption, to the financial detriment of IT operations that have bought many more servers and hard drive arrays than needed.
At the end-user level, who wouldn’t like a much faster PC, for instance? I installed an SSD and wouldn’t go back to HDDs! Every single user of IT systems sees improved system response and more productive as a result.
It’s time to step back, cut through all the hype and FUD and take a look at where solid-state drives and their associated storage are really at. We are going to take a peek at the key factors characterizing SSDs. We’ll address why they make sense, while covering the issues and myths that surround the technology.
SSDs are all much faster than HDDs. This is just physics: HDDs have mechanical head movement and rotational latency while SSDs do not. We are talking of 100X to more than 1000X the performance of HDDs, and this clearly positively impacts most use cases. An inexpensive SATA SSD can achieve 40,000 IOPS compared to the 150 IOPS of a typical SAS HDD, while streaming performance is around 5X for SATA SSDs.
High-end NVMe SSDs do even better, with millions of IOPS and gigabyte transfer rates as much as 20X the best HDD.
(Image: D3 Damon/iStockphoto)
As of 2016, the highest capacity drives are SSDs. Capacities of nearly 16 TB are available, and in a 2.5 inch form-factor. With HDD capacities essentially stalled around 10 TB until HAMR (laser-assisted writing) arrives, the SSD is well into the lead and, moreover, with 3D NAND flash, moving ahead at a fast pace. The industry expects to see 30 to 50 TB flash drives in 2020.
The high IOPS make such capacities usable. Until the SSD, any capacity increase reduced the IOPS/TB and this was becoming a major issue for access speed and RAID recovery.
(Image: Samsung 15.36 terabyte SSD)
Many people assume that SSDs cost more than HDDs, but the reality is very dependent on where you buy and what you buy. Most server and storage vendors added identification features to hard drives to prevent the use of commodity drives. This allowed huge markups on drives, as much as 20X in some cases.
The reality is that, in distribution, SATA SSDs are less than 50% of the price/TB of “enterprise” SAS HDDs. It’s been argued that SAS SSDs are faster and have dual-pathing through 2 SAS ports, but most apps written for HDDs won’t notice the difference, while dual-pathing is irrelevant in the new storage model of replicating data between servers or appliances.
We can expect substantial price drops in the next 18 months as 3D NAND matures, while advances in wear-life allow smaller die feature sizes and even 4-bit NAND cells (QLC) into mainstream use. I’ve reported in the past that Intel expects price parity with bulk SATA HDDs in 2017 and I think this is likely to be within reach.
Another common misconception about SSDs is that they wear out. Technology has really addressed this and SSDs will live long enough that they will be running when the server is scrapped. There are a few use cases where write wear is still an issue, but drives are available, at a premium, for high write-level situations.
It’s interesting that HDD vendors now specify a wear-life for HDDs. These are very comparable with SSD numbers, which means that this is a dead issue. As mentioned previously, new technology is increasing wear life on SSDs by large factors (as much as 100X), which will lead to denser and cheaper SSDs in a year or so.
Generally, having no moving parts makes the SSD inherently more reliable than an HDD. Spinning drives are prone to shock and vibration, as anyone who’s seen drives fail in hours due to rotational vibration from all the head positioners on other drives or from cooling fans in a system will tell you.
SATA SSDs typically use around 4 watts of power and idle at just a few milliwatts. HDDs use 12 to 20 W and idle at 8W. So SSDs are green! One bonus from the low power of SSDs is quiet servers, with both drives and cooling fans out of the picture.
Jobs run much faster with SSDs. That means getting more from fewer servers. The cost savings may be fast enough to justify moving to SSDs, especially if it obviates a server buy and allows the existing servers a longer life.
Even here, a little bit of analysis can save a lot more money, since often only some of the primary storage drives need to be replaced. Cold data can still be stored on the old HDDs