Hey, There’s an Elephant in the Room

When the first X25-M reviews went live a few people discovered something very important, something many of us (myself included) missed and should’ve addressed: the drive got slower the more you filled it up. It’s no great mystery why this happened, but it seemed odd at the time because it went against conventional thinking.


LegitReviews was one of the first to spot the SSD slowdown phenomenon, good work Nate.

It’s worth mentioning that hard drives suffer from the same problem; just for a different reason.

Hard drives store data on platters; the platters rotate while an arm with read/write heads on it hovers over the surface of the platter and reads data while the platter spins. The diameter of the platter is greater the further out on the platter you go, that’s just how circles work. The side effect is that for the same amount of rotation, the heads can cover more area on the outside of the platter than on the inside.

The result is that transfer speeds are greater on the outer sectors of the platter than on the inner ones. OSes thus try to write as much data to the outer sectors as possible, but like beachfront property - there’s only a limited amount of space. Eventually you have to write to the slower parts of the drive and thus the more full your drive is, the slower your transfer rates will be for data stored in the innermost sectors.

Fragmentation also hurts hard drive performance. While modern day hard drives have gotten pretty quick at transferring large amounts of data stored sequentially, spread the data out all around the platter and things get real slow, real fast.

Randomness is the enemy of rotational storage.

Solid state drives aren’t supposed to have these issues. Data is stored in flash, so it doesn’t matter where it’s located, you get to it at the same speed. SSDs have +5 armor immunity to random access latency (that’s got to be the single most geeky-sounding thing I’ve ever written, and I use words like latency a lot).

So why is it that when you fill up a SSD like Intel’s X25-M that its performance goes down? Even more worrisome, why is it that when you delete data from the drive that its performance doesn’t go back up?

While SSDs are truly immune to the same problems that plague HDDs, they do also get slower over time. How can both be true? It’s time for another lesson in flash.

Why You Should Want an SSD The Anatomy of an SSD
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  • FishTankX - Wednesday, March 18, 2009 - link

    Also, I think the velociraptor vs X-25 figures are swapped. 6 odd ms for the intel drive and 0.11ms for the velociraptor.. Reply
  • Natfly - Wednesday, March 18, 2009 - link

    Reply
  • DangerMouse4269 - Tuesday, April 13, 2010 - link

    Nicely written. Even a very out of practice Comp Eng understood that. Reply
  • geekforhire - Monday, June 14, 2010 - link

    I have just replaced the hard drive in this 3 year old Dell Inspiron 9400 notebook computer with a new and very quick OCZ SSD, manually configured the partition with a 1024 offset, freshly installed the OS, freshly downloaded all of the latest and greatest drivers from Dell, and applied all currently available OS updates from Msft.

    The problem is that when the machine resumes from Standby, it will /reliably/ (4 out of 4 attempts) produce a BSOD 0xF4 after the power button is pressed to resume the machine from standby.

    Here's the sequence to recreate the problem:

    0) Machine is booted normally into Windows, and log in to an account which has administrative privs.
    1) Click on Start -> Shut Down -> Standby.
    2) See display turn black, disk I/O light flashes then stops, then the power indicator light begins to flash on and off slowly.
    3) Wait until the power light has made 2 slow flashes.
    4) Press the power button.
    5) See the Dell Bios splash screen, then disappear
    6) Boom: See the BSOD 0xF4

    The values reported after the STOP are:
    (0x00000003, 0x865b3020, 0x865b3194, 0x805d2954)

    Note that I've been in contact with OCZ before about this SSD+computer, because the previous BSOD that was produced was 0x77. Their recommendation was to create the partition with an offset with a 64 interval, and to reflash the SSD with their modern firmware. This was done, the OS was reinstalled as described, and now I'm getting a different BSOD code. Another mention was a question whether the notebook computer uses a SATA2 controller (definitely compatible) or SATA1 (which may have troubles).

    I've run Spinrite on the SSD, and there are lots of ECC errors being reported. I've been in contact with Spinrite, and they chalk this up to the SSD being chatty (which they like), but since SSD's are new and magnetic disks are common, they want to stay focussed on magnetic disks.

    When the machine boots back up, the OS reports that a serious error has occurred, and asks that a problem report be submitted, which I do. Then an attractive but somewhat generic page is displayed with common causes (Aging or failing hard disks, large file transfers from secondary media to local hd, loss of power to a hard drive, hard disk intensive processes (eg: antivirus scanners), recently installed hardware that might have compatibility and performance problems)

    Has anyone else encountered this kind of problem, and do you have any suggestions?
    Reply
  • angavar - Thursday, September 09, 2010 - link

    As a medical student I can appreciate a well researched and analytical article when I see it. This is by far the best computer hardware review I have ever read! Thank-you for your time and effort in producing what is clearly a thoroughly researched and detailed analysis. Reply
  • mac021 - Wednesday, October 17, 2012 - link

    Thank you for the lesson and helping me understand SSD drives. May I just ask for your advice...

    For everyday use designing and generating prototypes for websites and running typical office s/w like word and excel for long documentations while listening to music or just having some video play in the background, then the occasional gaming of, say Star Craft 2 and Dead Space 3, and lets assume I do this on a 5 hours a day average for 365 days in a year, how long before I need to replace an OCZ Vertex/Summit SSD? And does format/reinstall help in prolonging the life of an SSD just as it does for my old hard drives (from a computer that's 6 years old and counting)? Or there's no stopping the SSD's death after reaching 10,000 times of being erased and rewritten on? I'm not one who keeps upgrading or buying new computer systems for every new thing that comes out, i'm more of a keeper and maintainer for as long as the system servers my needs... but when I make a purchase, I make sure it will be enough to last me another 6-12 years IF possible! Which is why I'm still considering SATA for my next purchase late this year or early next year (and I'm only buying a new PC just because I made a mistake buying a foxconn motherboard that can't support anything higher than XP, not even Vista... weird, anyway I found that out too late).

    Also, would you know of a motherboard that supports SSD, Windows 8, Nvidea, third gen i5/i7, and up to 64GB ram?

    Thanks so much!
    Reply

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