Are SSDs worth the extra cost?

Are SSDs worth the extra cost?

Summary: Whether solid-state drives are worth considering over disks will come down to cost calculations involving performance and the nature of your datasets.

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TOPICS: Storage
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Can SSDs be as cost-effective as rotating media? That's the question posed by a thought-provoking analysis from George Crump, senior analyst at Storage Switzerland.

Your first reaction may be, "Of course not." But many find it's justified to pay for the extra performance, typically just for the data that's worth speeding up. For example, in a datacentre, you might speed up just a database's working set or, on a personal machine, just the OS and applications. Having the OS or a complex application such as Photoshop pop up in seconds is worth the price of entry.

As Crump points out, most cost-justification in the enterprise for SSDs is done on a cost per IOPS, not cost per GB. That way, you compare it with the cost of short-stroked disks, of whose capacity you might only be using 50 percent. The rest of the disk space goes to waste, along with the cost of spinning and cooling the things. SSDs score here.

According to Crump, they also score when you front-end a spinning disk system with an SSD cache but the performance calculation is more complex. Flash-storage vendors like to talk about how many extra IOPS you get and the time you save when using SSDs as a cache but never, in my experience, point out that this technique only works when the proportion of cache hits reach a certain level.

If there's a cache miss, you're into negotiations between disk systems:

Have you got this bit of data?
No.
OK. Do you know where I can find it?
Try over there.

Not pretty or desirable. But throw in some deduping and compression and, with luck and a following wind, you might claw back some half-decent capacity savings, though nowhere near the volumes you save when backing up multiple VMs or client PCs. That might bring the justification of SSDs closer into line.

In the longer term, and as flash memory prices fall, I wonder if we might not see more systems using some form of execute-in-place technology, where the distinction between memory and storage becomes more blurred, in much the same way as it is in mobile phones. I appreciate that's more in the way that it's described and used, rather than in reality.

In the meantime, flash-memory vendors mostly sell systems that use a disk interface between the computer — that is, the CPU and memory subsystem — and storage. Not only does this practice add upfront cost, as Crump points out, but it also adds to your opex, as you have to house and power those disk controllers, as well as keep their drivers up to date.

Alternatives are emerging, such as that from the likes of Fusion-io, whose PCI-E-connected flash memory storage goes some way towards mitigating this problem.

But for most organisations, this approach is both way too expensive and potentially limiting — just a single vendor sells the product so you'll need a strong justification.

Instead, when considering SSDs to boost performance, ask if it really is cost-justified, and whether your datasets are suited to the kinds of usage that SSD vendors envisage when showering you with shiny PowerPoint presentations.

Topic: Storage

Manek Dubash

About Manek Dubash

Editor, journalist, analyst, presenter and blogger.


As well as blogging and writing news & features here on ZDNet, I work as a cloud analyst with STL Partners, and write for a number of other news and feature sites.


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An IT journalist for 25+ years, I worked for Ziff-Davis UK for almost 10 years on PC Magazine, reaching editor-in-chief. Before that, I worked for a number of other business & technology publications and was published in national and international titles.

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39 comments
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  • spinning disks vs SSD

    A big advantage that SSDs have over spinning disks is that spinning disks fail at an elevated altitude. This may be a problem if a laptop with a spinning disk is taken on an airplane without pressurization or the pressureization fails.
    douglasbrett
    • SSDs have a limited number of writes

      And are actually a hell of a lot less reliable than HDDs

      Worst, when an SDD dies, the data is usually unrecoverable (or very expensive to recover), while data in HDDs are easy to recover at very low cost.
      wackoae
      • Just restore from backup

        You do have a backup don't you?
        ye
        • Restore from backup

          I've had 3 SSD's fail on me, and yes, I have backups. But here's the hassle:

          Drive fails.
          Get RMA from manufacturer (1-2 days).
          Mail drive back. Wait 1-2 weeks.
          While waiting, restore data to "traditional" hard drive.
          Receive new drive. Install, restore data.

          Don't get me wrong, I love my SSD as my boot drive, but I've spent quite a bit of time recovering from the failures.
          Dauplat
          • Restore from Backup

            If you have had that many issues, perhaps you need a new vendor? By the same token, and I am not attempting humor or disdain, but I keep a USB mechanical drive on standby that is backed up by exemption every week for my laptop. The laptop is also connected to continuous back up through a wireless connection to my Airport Extreme. You may want to consider such a schema for your data given the issues you seem to be suffering.
            ExEC135CrewDog
      • Well with the cost of SSD's

        the size of SSD's drives that come with systems are quite small. The most efficient way to use them is basically for your OS. That will also extend the life sincew there will be less writes. I added a SSD to my laptop. My system cam with 1 750 GB HD and i moved that to the second bay and I went from 1 minute boot to 25 seconds. I do use it alittle for apps but most of my important stuff is on the HD.
        Orlbuckeye76
      • Once upon a time,

        there was a memory technology that paired a 1T DRAM cell with a fairly standard 1T Flash cell, one above the other and a single transistor transfer switch. This puppy copied the Flash cell contents to the DRAM cells on power up, then ran like a DRAM as long as power was applied. It could do a complete DRAM to Flash cell transfer, on a block by block basis, as quickly as it could do a 5 DRAM cell refresh cycles and only did that on command. This was technology that just cried out to be used as SSD memory. I used it to make a data logger that had to be ultra reliable and it was fantastic for its time. Ordinary flash for SSDs is not a very good choice, IMO. Hybrid DRAM/Flash has unlimited write cycles (You only need to do writes when power is removed or files are closed for writes), is just as fast as Flash alone and due to its 3D structure, could be just as small. It would save a lot on complex algorithms to keep aggregate writes to a minimum as Flash cells wear out.
        RyuDarragh
      • Conjecture vs research

        @wackoae
        "[SSDs] are actually a hell of a lot less reliable than HDDs."

        You keep reiterating this based on a (presumably) bad experience you had but this has yet to be proven.

        You also never provide empirical proof of this assertion, other than anecdotally. Do you have any studies to offer up that indicate this clearly? For example, ones done by the Center for Magnetic Recording Research consistently claim otherwise.

        The best point you make is that data loss is often catastrophic and can be unrecoverable, and there are less "head's up" warnings given for pending failures by comparison to HDDs.
        klumper
      • Data Recovery; low cost?

        At very low cost? Obviously you have never had to have a mechanical disk recovered at your own expense. The cost for data recovery is NOT insignifigant.
        ExEC135CrewDog
    • HDDs and altitude

      Having spent a large portion of my time in the Air Force, and having been through several Rapid Decompressions, I assure you that you have greater issues over which to be concerned if you suddenly lose cabin pressure than a data burp.
      ExEC135CrewDog
  • The answer is: It depends.

    Just like everything else in life. There is no one answer to this question...at least not until the price / capacity comes more inline with non-SSD disks.
    ye
    • It depends simpified

      It really depends on something more basic: are you willing to physically split your computer workload + data between a system drive (SSD) and a storage/backup drive (HDD)? For any power user, and really, any modern, up to speed consumer, that amounts to the ideal setup currently.

      If one insists on a single disk drive at this late point, or simply cannot afford a secondary drive, a 120GB SSD will almost always do the trick. I say this because it would be quite doubtful that any given user in that restrictive boat would qualify as a "power user."

      Needless to say, there are always external HDDs one can hook up by means as simple and basic as USB or FW to provide the requisite storage space to meet one's needs if internal installation proves daunting. IMO, there's little to no reason to be without a SSD - for sheer performance gains alone - circa 2012. It amounts to what RAM bump-ups used to accomplish.
      klumper
  • And....

    No fragmentation issues to worry about. I haven't used a SSD in a computer, yet. But there might be less data corruption as well. Just a hunch. Fragmentation is a nightmare I don't want to deal with. Same thing with data corruption. If those two things either don't exist or not as big of a deal, then it is worth money, I (everyone) else would love it if SSD memory went down as fast as other chip prices. But it's a matter of these mfg processes to improve so they can get the yields up and meet demand. Plus, there are also speed and density improvements always coming down the road.
    RichDavis1
    • They are coming down in price.

      I don't foresee them matching the cost / capacity point of traditional hard disks anytime soon. But a usable (I don't consider 64/120GB usable) disk is going to affordable soon.
      ye
      • What are you storing?

        How is 120GB not usable? Windows is ~25GB, then add another 40GB for applications and some games. What else do you need? If you actually want to store large amounts of data that's what traditional hard drives are for. Even 80GB is usable.
        Bonesnap
        • Best use of consumer SSD = basic system drive

          64GB, 96GB and 120GB are perfectly suitable for XP, W7 and W8 system drives, the capacity range varying based on individual user needs. Anything more than this is overkill for 99% of the desktop computing population, to include power users.
          klumper
          • gamers maybe

            I believe there are games around that need huge amounts of space and if an SSD improves gaming speed then a larger one would be needed. Personally I have windows and all my programmes (not data) on my 120GB SSD and it has loads of space left
            cymru999
        • Basic system drive PS

          Basic system drive (SSD) = operating system, programs (applications + utilities). Optionally: favorite games. Optionally: personal data like Documents.

          Storage drive (HDD) = common backups, drive images, games, personal data like Music, Videos, etc. Optionally: personal data like Documents.

          Bonesnap is on the mark.
          klumper
    • Fragmentation is not caused by the drives

      The drive is just a storage device. Fragmentation is cause by the poor way the OS allocates memory spaces compounded by the poor programming habits of the developer.
      wackoae
      • Fragmentation is also

        caused by saving and deleting files. If you delete a file and then save another file thats bigger the file gets saved in non consecutive blocks. Thats affects retieving the data later.
        Orlbuckeye76