SSD vs HDD - Hosting Perspective

SSD vs HDD – Hosting Perspective

There’s been a big transformation in the way data is stored by web hosting providers. In the past majority of the web hosting companies used hard disk drives (HDDs) as the core storage devices. Now servers are increasingly using solid state drives (SSDs) to take advantage of the performance improvement. However, hosting providers whether offering budget shared hosting, virtual private servers (VPS) or indeed offering dedicated servers still offer a mix of HDD and SSD.  What’s the difference, which should you choose, and should you migrate to SSD if you’re currently on HDD-based hosting? Read on to find out.

SSD vs HDD – the basics, and why it matters

It can be difficult to figure out whether a hosting company uses SSD or HDD storage, particularly when it comes to shared hosting. Web hosts do not always advertise clearly that the hosting on offer is based on hard drives or solid state drives. That said, because solid state drives are faster, hosts that do offer servers running on solid state tech will usually mention it on their websites.

Before we go any further we should discuss exactly what the difference is between solid state drives and hard drives. Why? Well, SSDs are generally still more expensive than HDDs so the associated hosting is more expensive too. Knowing what the performance differences are can help you justify the cost.

The main differences between SSD vs HDD

The basics of hard drives

The 1950s saw the invention of what is today’s hard drive storage technology. It’s based on magnetics and operates in a way rather similar to the way a vinyl record does. The data on a hard drive is stored on a metal disk which is mounted on a wheel that spins it. Each drive has a sensor called a drive head which moves along the disk to find data. The head reads the data and sends it to the computer.

Hard drives on their own have different speeds, it depends on the rotation speed of the disk (5400 or 7200 RPM, for example) and also the bus which connects the hard drive to the motherboard. There are a number of bus types, two centred around ATA technology – parallel ATA and serial ATA – plus the more server-orientated SCSI and of course Serially Attached SCSI. Another server standard is called Fibre Channel.

Interestingly, there is a similarity between hard drives and floppy drives, the soft magnetic disks that were broadly used for data transfer and storage in the past. However over the years hard drives evolved to store far more data, a typical modern hard drive stores several terabytes (TB) of data.

Introducing solid state drives

SSDs or solid state drives only came on the computing scene around 2009. There are no physically moving parts in a solid state drive, instead solid state drives contain memory chips – just the same memory chips used in random access memory or a USB storage drive. Why use memory chips for long-term storage? Well, solid state drives offer much faster throughput – in other words data transfer speeds – compared to hard drives. That said, it is the seek times – in other words, the amount of time it takes to locate data – which are dramatically faster than hard drives.

In other words, an SSD drive can locate data nearly instantly whereas most hard drives have seek times of 10ms or more. This is because SSD devices do not have moving parts, but make use of ICs (or integrated circuits) instead. Benchmarks can reveal this quite quickly, solid state drives are overall able to transfer up to 95% more data under situations that heavily load the device, compared to a hard drive.

Benchmarks also show that SSDs generally respond to input/output requests up to 20 times faster than a hard drive. Note that, just like hard drives, solid state drives also perform better depending on the bus the drive sits on. The fastest drives are directly linked to the computer by means of PCI-express, but in servers fast SSDs will be on Fibre Channel or Serially Attached SCSI as it is a practical way to connect a lot of drives in a redundant manner.

HDD vs SSD – the important distinctions you need to be aware of

Just like any new technology, SSD vs HDD cost was really high when solid state drives were first launched. Even SSD drives with little storage capacity were extremely expensive, matching large hard drive capacities was exorbitant. So for the first few years it was only elite hosting or high performance server hosting where providers would use solid state drives in their machines.

The slow shift is also in part due to the fact that servers are purchased in cycles, most hosts would only replace servers every few years and hosts were not interested in paying big amounts for solid state drives at the time.

SSD vs HDD: solid state costs rapidly dropped

But, solid state drives are becoming much cheaper. Consumers demanded the faster performance and SSD manufacturers managed to reduce the costs in their manufacturing processes. As a result SSDs have started to replace hard drives across the hosting spectrum. Hard drives are still significantly cheaper on a gigabyte for gigabyte basis nonetheless solid state drives have taken over with most cloud-based hosting now operating on solid state drives.

It is only budget hosts that will offer hosting that is based on hard disk drives exclusively – think cheap shared hosting plans and so on. There is also another concern with hard drive: they fail more frequently, however hosts will usually have redundancy in place to prevent data loss and service disruption. Because hard drives are so cheap it is easy to implement redundancy, but it erodes some of the cost advantage of hard drives. HDDs are still very effective for offsite storage, archival purposes and general backup duties.

Device reliability

Equipment with moving parts fail, and this is the case with hard drives too. Mechanical devices rarely function forever across the board, device by device. Different variables can contribute to failure rates, including heat and load factors. As much as rack mounted machines are not subject to movement and vibration the way desktops and laptops are, heat and high server loads plus the round-the-clock requirements of servers can mean that hard drives fail fairly frequently in server scenarios.

SSD vs HDD: solid state is more reliable, but not infallible

We know the solid state drives do not have a problem with moving parts. Another reason why SSDs perform better than hard drives in terms of reliability is the fact that SSDs respond to requests faster, like we said – up to 20 times faster. This means a solid state drive is less likely to be overloaded by requests. Equipment that is frequently strained can eventually lead to mechanical failure.

However SSDs have a different, unique problem not faced by hard drives. An SSD can deliver missed writes and bit errors if a specific sector of an SSD is read into frequently. This is due to something called electron tunnelling, but this problem can be mitigated by the firmware on an SSD. In fact, SSDs have come a long way as various SSD-specific issues have slowly been eliminated in large part due to firmware.

What do the benchmarks say?

Well the best way to judge HDD vs SSD in terms of reliability is to look at the benchmarks. Hard drives would typically fail at a rate of 3.5 out of 100 throughout the lifetime of the device. SSD’s would fail at a rate of 0.5 out of 100. That’s a seven-fold difference.

The high failure rates of HDDs are the reason why RAID (Redundant Array of Independent Disks) storage has become so important over time. With RAID data is mirrored across drives so that if a single drive fails the data is not lost, instead the data can be rebuilt on a new drive.

Compensating for device failure – necessary for both SSDs and HDDs

Almost every virtual host will use RAID on their machines to ensure that their customer data is safe if a physical drive fails. RAID quickly becomes complicated and can be expensive to implement where a company has multiple data centres distributed around the country, and where data is stored offsite.

However for most hosting plans that are sold retail RAID will not be something the customer needs to worry about. The host will take care of RAID concerns. It is only clients who make use of private cloud or cluster service that are elastic who will need to be concerned about which RAID regime they will implement. This also goes for managing the overall backup strategy as dedicated hosting and private cloud solutions require real disaster planning to mitigate system crashes and hardware failures.

Devices speeds and the impact on hosting

Easily the primary factor for choosing an SSD over an HDD in the hosting scenario is speed, and that’s the case especially where web hosting is concerned. The reason for this is the high transaction volume and hence high number of disk access requests generated by web hosting. However, from a practical perspective, it is only websites which experience high loads or where hosts try to pack a lot of websites into a shared hosting environment. Here website owners will really lose out if they sign up with a hosting plan that puts high server loads on hard drives, this will put their sites at a competitive disadvantage.

Mitigating the problems with hard drive speeds

Of course, web hosts can do a lot to mitigate problems around hard drive performance and they often do so to enable the ongoing use of hard drives, which in turn reduces the costs associated with hosting. For example, a host can choose to store data-intensive applications like MySQL on hardware with solid state drives, while serving media files from a hard drive-based machine.

Using file caching based on reverse-proxy is another option, alongside load balancing to take the load off a single machine and its individual hard drives. With multiple copies of the same website running a host can manage demand in a way that hard drives can cope with. Thanks to load balancing traffic is routed to machines with a lower load so legacy hard drive-based servers can provide reasonable response times.

There are more factors, of course. A content delivery network or can also bypass hard drive performance shortcomings, and so can the use of caching and virtual RAM. Web hosts usually manage domain services for companies so they can run DNS requests, which require fast responses, through a machine that uses SSDs. On the flipside the host can put websites with little traffic on legacy machines that makes use of hard drives.

In fact, many hosting plans include CDN as an option because it is so effective at mitigating slow hosting speeds where hard drives are the culprit. That said, nowadays hosts also offer solid state hosting as a benefit above CDN, even if this is more expensive and effectively premium-priced. All that said, it’s not uncommon that a basic shared hosting solution will be relegated to hard drive-based servers.

SSDs count for overall performance

Particularly where virtual RAM solutions are used in shared hosting accounts to boost RAM available to content management system (CMS)-driven sites, hosts must make SSDs available to customers in their hardware to ensure the CMS systems run fast. Hard drives can result in slow response times. Many hosting companies have opted to offer cloud virtual hosting plans which are based on SSD hardware to ensure customers get better performance, but these would come at a higher cost than the host’s equivalent HDD-based hosting solution.

SSD vs HDD power consumption

Web servers consume a lot of power and according to the IEEE up to 35% of the power consumption of a server is due to storing data. It adds up to large numbers, $20bn is spent annually on electricity by data centres around the world.

SSDs save the day

Solid state drives consume a lot less power and for this reason stand to bring environmental benefits to the hosting and data centre fields. The reduced electricity use associated with SSDs can save a lot of money. Benchmarks suggest that a solid state drive will use 0.38w for every hour it idles, 0.68w for every hour it performs read operations, 2w for every hour it performs a database processing function and 3.01w for every hour that the drive is writing at its maximum speed.

How do hard drives compare? A normal HDD would consume fifteen times the power of an SSD while idle. The power usage difference is less under load, but still significant with HDDs using about 2.5 to 7 times more power under heavy server load compared to SSD drives.

According to a study performed by one of the world’s biggest hosting providers, Rackspace, the difference in power consumption when comparing HDD vs SSD is not large enough to recover the difference in cost, even over a period of up to five years. However there is still a degree of savings involved where companies run major data centres as SSDs also require less cooling. In contrast HDDs can generate a lot of heat.

Points to note around durability

Overall when looking at SSDs vs HDDs it is clear that a hard drive is more likely to fail. Statistically hard drives fail at a rate of 3.5 out of 100 across a three to five year usage period, while solid state drives will fail at a rate of 0.5 out of 100 over a period of three to five years. Interestingly the failure rates for hard drives vary across their lifetime. In year one, the failure rate is about 5 in every 100, dropping to 1.4 out of 100 in year two, jumping to almost 12 out of 100 in year three.

Why hard drives fail more frequently

The reasons are myriad but are mostly due to issues during manufacturing or problems with the hard drive firmware. Of course the ongoing use in a strenuous environment such as web hosting will lead to failure rates too which is why hard drives start seeing increasing problems in year 3. Other factors that influence hard drive failure include the manufacturer as some are more reliable than others while spin speeds and bus types can also have an effect.

How SSDs compare to HDDs

The reason for SSD failure is however very different. In the case of solid state drives the reason for failure is mostly because a specific block is written across far too frequently. Good drives will include an algorithm in the drive’s firmware that levels out the wear on the drive so that the strain on the NAND chips are lessened under demanding scenarios.

Though solid state drives are slowly replacing hard drives in the server environment there is not yet enough data to understand how SSDs perform in the live environment, and whether SSDs are statistically less likely to fail than hard drives under the strenuous demands of web hosting. However, the expectation is that SSDs will have a longer production use than hard drives, outlasting the five to six-year lifespan of HDDs.

Overall estimates suggest a ten to twenty-year lifespan for solid state server storage hardware which more or less means the drives will last as long as the equipment is used for. Most hosts will upgrade servers far faster than a ten- or twenty-year interval so it’s likely that solid state drives will never see the need for more than just the odd replacement in a server scenario.

HDD vs SSD costs

SSDs are clearly much faster than hard drives and are also more reliable. The only reason SSDs are not adopted more widely is that they are so much more expensive than HDDs. This is why SSD implementation has been held back over the last decade. How much different are the costs exactly? Well estimates suggest that solid state drives are about four times as expensive as hard drives on a per-gigabyte basis.

Of course, in high-performance server environments the extra cost can easily be justified due to the up to twenty-times faster server performance. This huge performance difference can be massively beneficial for web hosting and mobile apps that need to scale to serve large audiences.

But for web hosting and low-demand server scenarios the benefits of solid state drives are not always that clear. Under these scenarios hosts can often operate at extremely small margins which means that there is not much room to splurge on hardware. For these hosts the HDD to SSD switch has been very slow. Even in 2018 many shared environments are still driven by what is now relatively slow hard drive technology.

Unlimited storage keeps SSDs out of shared hosting

Cheap hard drives has made the provision of “unlimited” hosting plans which puts no caps on storage consumed by clients possible. However, it is difficult to offer a hosting plan with no caps on storage when SSDs are in use by the hosting provider. This has stopped SSDs from being adopted in this sector of the market.

On the flipside clients who pay for dedicated servers or virtual private servers have come accustomed to premium pricing and are generally willing to fork out for SSDs in return for the better performance. With Google now evaluating search engine rankings in part on page load speeds many website operators are opting for hosting on solid state drives thanks to the faster performance.

SSDs are appearing in budget options

Yet with budget hosting where fees are only a couple of dollars a month solid state drives are starting to make an appearance; though SSDs are not yet widely available in budget hosting. Shopping around can be a good idea, you may be surprised to find that some affordable shared hosting providers offer hosting plans with solid state drives. Importantly, don’t get locked into a plan which forces you to stick with hard-drive based hosting in the long run, particularly if you are buying a plan for dedicated server provision or a virtual private server.

How you should decide between SSD vs HDD hosting

Solid state drives are changing the hosting environment for the better and have been doing so for almost ten years. SSDs allow much faster transactions for databases and improves web site loads speeds tremendously. That said the hardware investment cycle has hampered SSD adoption, while hosting providers are also waiting for costs to go down.

When choosing you should look at your own hosting requirements. If you need high performance in 2019 you should not even consider a hosting plan which depends on hard drives for storage. You have a lot of options when it comes to Windows or Linux shared hosting as most providers can now provide a solid-state drive option.

Yes, you can obtain a discount by choosing a hard-drive based dedicated server or virtual private server but you are looking at a huge drop in speeds, with hard drives up to twenty times slower than solid state drives. For most clients the huge drop in performance is not worth the small savings, and this is particularly true where a content management system is used to drive a website.

Is it worth moving your hosting to an SSD-based server?

Purchasing a new hosting solution is one question, but another question surrounds whether you should move from HDD-based hosting to SSD-based hosting. If you’re on shared hosting you are probably getting about 0.5GB to 1GB in RAM alongside unlimited bandwidth and storage, and unlimited domain names. Some hosts will provide a virtual RAM allocation that is based on a disk.

Most website operators should consider moving to SSD-based hosting if they are currently making use of a hosting plan that is based on HDDs, and can probably do so on a plan that costs more or less the same. In particular, any solution that uses virtual RAM is not really well-placed to run a website driven by a content management system. However, if this virtual RAM is based on a solid state drive the performance becomes similar to real RAM.

In practice it is worth paying just a bit for SSD vs. HDD hosting for any website that runs PHP or a database such as MySQL. That said if you are really on a budget you could consider a basic hard drive-based solution that is backup up by a content delivery network or another type of website cache; these can bridge the performance gap between solid state and hard drive-based hosting.

When is it worth choosing HDD-powered servers in the HDD vs SSD debate?

Budget website hosting providers have been very innovative when it comes to fixing the performance problems of hard-drive based hosting. For example, load balancing can help hosting companies that still use hard drives compete with their peers who have switched to solid state drives.

Some sites do not need solid state drives for high performance: a website which is based on static HTML files do not draw on server resources very much in won’t see much benefit from solid state drives in the HDD vs SSD comparison.

Where large files are handled, such as archival tasks, or where hosts are operating a download or file storage service the need for solid state drives are reduced because of the low rate of file access. Here you can save a fair amount of money by opting for hosting solutions based on hard drives.

Likewise, a blog site with a single user and perhaps up to 2,000 page views a day can make use of content delivery networks and caching to manage demand, and to remain on affordable hard-drive based hosting servers. Here hosting can be just a few dollars a month, easily, which can be very attractive for some website owners.

Finally, where you own several website that are currently operating at sufficient speeds it may not be worth the time and effort involved to change to another host to enjoy solid state-based hosting, as long as the existing hosting solution is providing adequate performance – and particularly where you are already locked into a discounted hosting plan that is in place for the long term

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Elvis Plesky
Our fun and curious team mascot's always plugged into the latest trends. He's here to share his knowledge and help you solve your tech problems.

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