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Business Metrics

SSD 102: The Ins And Outs Of Solid State Storage
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Let’s look at these metrics for a moment. If you've never studied the differences between SSDs and hard disk drives (HDDs) before, the comparisons can be striking. Although this data comes from a Samsung presentation on green SSDs and their benefits, the numbers correspond with our test results in prior articles.

We don’t want to comment on the gigabyte per watt section, as capacities are usually least relevant in this context. Yet we’d like to point out that SSDs of up to 512 GB per drive are available, basically matching 2.5” enterprise hard drives at 300 GB and 600 GB peak capacity points. In maximum I/O scenarios, where capacity hardly counts, a 64 GB SSD can even be cheaper than a comparable 73 GB enterprise HDD. As a result, SSDs are more relevant for I/O-intensive business applications than client PCs given their cost and performance attributes.

Capacities aside, you can’t really argue with SSDs' I/Os per dollar and I/Os per watt, as SSDs are typically much faster than hard drives while consuming a fraction of the power. Hard drives generally deliver between 100 and 400 I/O operations per second, depending on block size and random/sequential access. SSDs can hit five-digit I/O operations per second results.

In other words, SSD cost per gigabyte is comparable to HDDs while SSD cost per I/O trounces its magnetic competition, yielding a break-even on total cost of ownership. Effectively, you could deploy a single SSD to replace the I/O performance of dozens of hard drives or replace a certain amount of hard drives with SSDs, multiplying performance while still lowering power consumption. Also think about power and cooling requirements, which might decrease significantly thanks to a few SSDs potentially replacing an entire server rack.

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  • 2 Hide
    LaloFG , September 11, 2010 10:05 AM
    Very good article; times of most affordable capacity in SSD units is coming...
  • 1 Hide
    Lewis57 , September 11, 2010 11:03 AM
    A very good article. I love these articles explaining everything. I'm planning on buying two OCZ Vertex 2E 60GB for RAID-0 when I get enough money. Can't wait, should be one hell of an upgrade from a single 5400rpm WD green drive.
  • 0 Hide
    ares1214 , September 11, 2010 12:32 PM
    Memristors might make SSD's sorter lived than people thought, but who knows. Great article btw.
  • 0 Hide
    JoeSchmuck , September 11, 2010 3:18 PM
    From what I understand, TRIM is supported under IDE mode using Win7 as well so you do not need AHCI. I have a Samsung’s VBM19C1Q firmware device and running IDE mode.
  • 0 Hide
    hemburger , September 12, 2010 12:17 AM
    Great article!! :D 
  • 0 Hide
    Anonymous , September 13, 2010 2:04 PM
    Earlier this year we deployed a 5 node failover cluster with iSCSI backend. Each of the VM Host servers utilize a pair of solid state drives for booting and operating, with VM's running off of iSCSI shared cluster volumes. The servers are unbelievably fast and stable - 6 months of 100% uptime on Windows 2008R2. We only use magnetic HDD's now for transporting backups off site.
  • 0 Hide
    Anonymous , September 13, 2010 7:47 PM
    One thing that I'm very curious, if we follow Tomshardware's advice to turn off disk defragmentation, the files on SSD would be defragmented over time.

    Upon SSD data loss, can we recover the data files if it's defragmented, especially on a SSD that has never been defragmented as Tomshardware had recommended?
  • 0 Hide
    randomizer , September 14, 2010 7:25 AM
    Defragmentation of an SSD is not entirely unnecessary. It's important to distinguish between file fragmentation and free space fragmentation. The former is not an issue with SSDs because all parts of an SSD can be read at the same rate (the same is true for writing if the blocks are clean). But fragmentation of free space, whereby free space is largely distributed across partially-filled blocks, can severely reduce the performance of an SSD. Any time a file of <512kB is written to an SSD, it will take up only part of a block. However, the SSD will eventually run out of clean blocks and will need to re-arrange the data by erasing partially-filled blocks and consolidating them to free up more blocks for further writing. Running a free space defragmentation on the drive will aggressively consolidate the data on-demand so that you don't have the problem occurring when you didn't plan for it.

    Most SSDs will perform this process themselves when idle for extended periods, but it happens at a slow rate. This is what most manufacturers refer to when they talk about Garbage Collection.
  • 0 Hide
    Alvin Smith , September 14, 2010 7:31 AM

    Please send me the four fastest 256GB SSDs on the market, so that I might perform my own comparison ... I'll just sit by the door and wait for UPS to arrive.

    Thanks, in advance !!

    = Alvin =
  • 0 Hide
    gordonaus , September 14, 2010 1:02 PM
    I put an SSD in my new computer and it was good but after i got the firmware update and changed to AHCI it was AMAZING (OZC Vertex 2 60gb). I would say tho that 60 gb is not enough, i installed windows photoshop and a few other design programs and i only have 20GB left
  • 0 Hide
    compton , September 14, 2010 5:38 PM
    Great article. I'm happy to see it in the mix. I'm sticking with my Intel x25-V and OCZ Agility 60 for a little while, but who knows what the future will bring.
  • 0 Hide
    cadder , September 14, 2010 6:31 PM
    I haven't seen this addressed before- how does the reliability and data safety of an SSD compare to a mechanical hard drive?
  • -2 Hide
    Anonymous , September 15, 2010 1:25 AM
    It is much cheaper to buy 2 Hitachi 7200K disks which are quite reliable and compact RAID enclosure like Jou Jye. And you can have same SSD performance with 1TB drive for the price of one 256GB SSD. I have to mention that I can have up to 2,5Gbps max transfer rate which is not far from SATA II limit.
    I am using same configuration on desktop. What I have noticed is that performance is actually much better than I expected. That is probably because of cache memory. If you have drives with big cache then in RAID stripe configuration those caches logically combine. In case of good desktop drive you can easily have 64MB cache. BTW I looked at the SSD drives caches - wow I know where performance comes from. :)  Actually not from SSD technology as such.

    I think SSD is overrated right now. They have to be 4x cheaper. Otherwise it makes no sense. Next year they will be 2x cheaper and after one more year they will 2x more cheaper. So actually technology still needs two years to be usable.

    My recommendation: stick to SATA and RAID - save the money. If you need little storage and max comfort then use SSD.
  • 0 Hide
    d1rtyju1c3 , September 16, 2010 12:06 AM
    This was a great article. I learned alot of new thing I never knew about SSD's. Now I will be able to make a better selection when I add a SSD.
  • 0 Hide
    Keeper , September 16, 2010 1:24 PM
    dvdeo,

    You save a lot of money with SSDs, simply because their watt consumption is really low. So, in long term (say 1y) you will be saving enough money to probably buy those Hitachi 7200K for free.

    Energy efficiency is the key factor with SSDs.
  • 0 Hide
    JoeSchmuck , September 16, 2010 9:59 PM
    I understand data reliability for SSD cells that may have reached thier maximum writing number, that the cells can still be read making the data at least available which is much better than a mechanical hard drive since when they fail, ut's usually not good.
  • 0 Hide
    bitterman0 , September 21, 2010 8:14 PM
    Keeper... So, in long term (say 1y) you will be saving enough money to probably buy those Hitachi 7200K for free...

    The power consumption difference of a single drive is negligible for the purposes of generating any tangible savings on the electric bill. Let's assume the average power consumption difference between HDD and SSD is 5W, and the system that employs the drive is up 24/7/365. Also, let's assume that your electricity cost is 14 cents per kWh (that's what I'm paying on average, your mileage may vary). Thus 0.005kW * 24h * 365d * $0.14 = $6.132 - that's your annual savings (to be clear, that's six dollars and some change, not six thousand). Surely, if you employ hundreds upon hundreds of drives, the savings will add up, but in the end the up-front investment into SSD's higher cost is not likely to pay off within the SSD lifetime, not to mention to get you any savings.

    On a separate note, I do believe that longevity of drives is one of the major factors that affects the purchase decision. For enterprise use, if the drive is constantly hammered by writes (say, a database file is stored on it), the rate of wearing out re-writable flash is likely to be higher than the rate of failure of magnetic drives (certain 10K RPM IDE drives notwithstanding).

    ... if only SSD were more affordable! But, perhaps, the rumored adoption of 2Xnm technology for NAND by Intel by the end of this year will finally put enough pressure on the market to bring down prices to the realm of affordability. One can only hope.
  • 0 Hide
    doorspawn , September 27, 2010 10:17 AM
    Can someone shed some light on a query I'm sure many of us have here:

    Why is the block size so large?
    What makes a 4KB or even 256B block a bad idea?
    Is it there's a large per-block component that can't be shrunk?
    Is it that blocks need to be insulated from each other so that high-voltage instructions (perhaps clear) don't leak?
    Those are purely guesses.
  • 0 Hide
    Anonymous , September 28, 2010 5:09 AM
    Good overview article, error on last graph:
    5.5 watts to 1.7 watts is not "1/3 Reduced" as per label - it is "2/3 reduced" or "Reduced to a 1/3"
  • 0 Hide
    dEAne , October 4, 2010 9:55 AM
    thanks for this article.
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