When does Random / Sequential Reading and Writing come into Play?

Discussion in 'Storage Devices and Memory' started by TheFocusElf, May 3, 2010.

  1. TheFocusElf

    TheFocusElf Obliviot

    Mar 1, 2005
    SSD comparisons can be fun. Building a new system for my boss this time, I might be inclined to swap a few of my SSDs for hers!

    Namely my boot drive - Crucial's RealSSD 300. Great at sequential, apparenlty awful at random.

    This made me wonder, and google couldn't help me - when do these two come into play? When does it matter?

    Listening to MP3s
    Playing a single player not online game like Bioshock 2
    Playing a MMO (WOW, KoTR [so awesome!])
    Rendering AVCHD content of the 3 week old into a quicktime HD Movie to pop on the wife's iPad

    What kind of operations, in lay-man's terms, depend on sequential and which on randoms?

    I did spend a while googling after replying on the DRM thread, and to be honest, nothing answered my question directly!

    If you want to go for extra credit, in the SSD world, where these new SandForce controllers are concerned, how can an SSD like the Crucial listed above perform so drastically different than a Corsair Force 200 for instance (the drive that is captivating my interest at the moment for a boot/os/programs drive).

    Much love to the TG community as always.

    Edit : Someone emailed me asking about Star Wars Old Republic online... no I am not playing it, I am sure Rob knows some folks too in early alpha tests - I am just very excited for it an NO I am not a SW nerd and never even played galaxies once.
    Last edited: May 4, 2010
  2. Kougar

    Kougar Techgage Staff Staff Member

    Mar 6, 2008
    The RealSSD performs very well with random writes... if you use any OS other than XP. It is second only to Sandforce drives. It also offers the highest random reads so far. Link

    The problem is... the drive suffers from a risk of unrecoverable performance degradation just like Intel's X25-M G1 did. And just like Intel, the firmware fix is bricking drives and was pulled. Anand has even managed to induce one into a "comatose" state, not dead but not very unresponsive.

    Right now I wouldn't trust one with my data... but I'm not sure about Sandforce yet either as the drive technology is unique and the controller unproven. I have already had one review SSD fail on me, so Anandtech isn't the only one capable of finding ways to brick SSDs during everyday use. ;)

    Random reads would mostly be Anti-virus, Search indexing service, and programs of that nature.

    Sequential can be thought of as file transfers, high definition video file creation, or even large music file creation. Sequential reads could count as loading your mp3 into memory for playback. The most clear example would be file transfers... say moving a file from one disk to another, or from your drive to a networked location. Working with large 1-50mb files in Photoshop, or other large file sizes for any other application, etc.

    The OS is going to be more random reads/writes because it has files scattered all over the place, some being read, others open in memory and being periodically updated, or writing new files such as logs, browser cache, search history, etc.

    The performance is not that different. In fact the Sandforce drives's largest competitor is the RealSSD drives. Those are the two highest performing controllers available right now.

    That said, the Sandforce SF-1200 operates completely differently than the customized Marvel controller that powers the RealSSD. Keep in mind for an SSD the bottleneck is always going to be the NAND flash.

    The Marvel controller is like Intel's G2 and Indilinx's Barefoot controller in that they all use somewhere around 4-10 channels, each channel has dedicated NAND flash chips, and the controller uses some advanced logic to figure out which flash channels to utilize simultaneously to get the highest performance. It needs to organize the data to write into clumps and then distribute it to one or more flash channels, it requires a powerful controller with advanced algorithms and logic... and generally the more flash channels the more room for performance. The more operations it can carry out at the same time, the higher the performance you are going to see.

    Sandforce mixes things up by turning the problem the other way around. Their controller compresses all data... it looks for data that can be compressed (not all data is compressible, say for example any already compressed media file, jpg, or a zip or rar file sitting on your desktop). The act of compressing a file works by removing duplicate information from it... which makes the file size smaller. Their controller needs a different sort of advanced logic and must be powerful to compress data in real time on the fly.

    So, when all is said and done lets say the controller compressed a 50MB file into 20MB, it would only have to write 20MB to the flash. Intel's G2 or Indilinx's Barefoot would have to write the full 50MB by comparison. Sandforce, by compressing data means it has less data to write and hence it completes the same task "faster" as it were. It's a really novel, if overtly complex method of working around the NAND bottleneck. But many file types are already compressed and can't be compressed further, which means the sandforce controller won't always perform at its best.
  3. TheFocusElf

    TheFocusElf Obliviot

    Mar 1, 2005
    Very thorough and informative Kougar, thank you very much - as mentioned most of the resources I found either made the concept extremely abstract (I didn't do well in Calc 2 at Syracuse...) or just didn't do anything to answer the question. I am keeping one of the RealSSDs for myself!

    So given that you are the SSD Guru around here let me lay out my drive situation and my proposed drive allocation:

    [A] Crucial Real SSD
    [B] Corsair P256
    [C] Corsair X128
    [D] WD 300GB Raptor
    [E] WD 300GB Raptor
    [F] Toshiba 320GB 7200RPM - Factory Laptop Drive
    i7 965 System
    [A] For OS Boot, Programs and Games? Do SSDs respond well to partitions? Does that help with Stability? in other words, I don't really do a lot of file modification on a boot or program drive except when a program is initially installed. I typically disable automatic updates universally, in favor of a periodic search for major patches.
    [E] System Documents, Downloads and work Files
    [F] iTunes and Photo and Video Media

    Asus Laptop
    [C] For Boot, Programs and maybe a game or two
    [F] For files and storage

    What the blazes do I do with the P256 short of build a new system or use exclusively for games and just waste a ton of the drive...

    When you went in to describing searching, and virus scanning, I will tell you point blank that I disabled windows search indexing process. Additionally, I rarely and by rarely I mean never virus scan. I really only run programs, and do video and audio encoding. I use After Effects - A LOT.
    Last edited: May 5, 2010
  4. Kougar

    Kougar Techgage Staff Staff Member

    Mar 6, 2008
    There isn't any reason to mess with partitions, unless you wish to have clearly defined segments of the drive for temporary file storage, scratch disks for program use (Photoshop has a scratch disk option if you work with extremely large files), etc. There isn't much reason to do so for security anymore, and except for benchmarking I don't use partitions at all anymore. Most SSDs are too small anyway for it to be worth it. :)

    I rely on indexing for quick searching, especially from the start menu, but it's a matter of personal preference really. Full scans might take a long time given it would scan all drives, but after a full system scan MSE only performs a quick scan as part of it's weekly routine. Even with a HDD it takes less than a minute to complete.

    As for what to do with your P256, ya can sell it to recoup the costs, keep it as a backup drive, or whatever. Personally I'd put my games on the Crucial drive, especially if it is the 256GB version, but you could very easily put them on the P256. Depending on the work you do, you could even use it as a scratch disk for the content creation programs you use.

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