The Downside: Consistency

Initially it's very easy to get excited about Intel's SRT. If you only run a handful of applications, you'll likely get performance similar to that of a standalone SSD without all of the cost and size limitations. Unfortunately, at least when paired with Intel's SSD 311, it doesn't take much to kick some of that data out of the cache.

To put eviction to the test, I ran through three games—Portal 2, Starcraft 2 and World of Warcraft—then I installed the entire Adobe CS5.5 Master Collection, ran five of its applications and tried running Starcraft 2 again. All of Starcraft 2's data had been evicted from the SSD cache resulting in HDD-like performance:

Starcraft 2 Level Loading—Seagate Barracuda 3TB (Maximize Cache)
  Load Time Load Time After App Install/Launch
Game Launch 9.7 seconds 17.4 seconds
Level Load 15.0 seconds 23.3 seconds

I thought that may have been a bit excessive so I tried another test. This time I used the machine a bit more, browsed the web, did some file copies and scanned for viruses but I didn't install any new applications. Instead I launched five Adobe applications and then ran through all of our game loading tests. The result was a mixed bag with some games clearly being evicted from the cache and others not being touched at all:

Game Load Comparison
Intel SSD 311 20GB Cache Portal 2 (Game Launch) Portal 2 (Level Load) Starcraft 2 (Game Launch) Starcraft 2 (Level Load) World of Warcraft (Game Launch) World of Warcraft (Level Load)
Load Time 9.9 seconds 15.1 seconds 9.7 seconds 15.0 seconds 4.5 seconds 5.8 seconds
Load Time After Use 12.1 seconds 15.1 seconds 10.1 seconds 15.3 seconds 3.6 seconds 14.0 seconds

Even boot time was affected. For the most part performance didn't fall back down to HDD levels, but it wasn't as snappy as before when I was only running games.

Boot Time—Seagate Barracuda 3TB (Maximize Cache)
  Time
Boot Time 32.6 seconds
Boot Time After Use 37.3 seconds
Boot Time Without Cache 55.5 seconds

Although Intel felt that 20GB was the ideal size to balance price/performance and while SRT is supposed to filter out some IO operations from being cached, it's clear that if you frequently use ~10 applications that you will evict useful data from your cache on a 20GB SSD 311. For lighter usage models with only a few frequently used applications, a 20GB cache should be just fine.

There's also the bigger problem of the initial run of anything taking a long time since the data isn't cached. The best way to illustrate this is a quick comparison of how long it takes to install Adobe's CS5.5 Master Collection:

Install Adobe CS5.5 Master Collection
  Time
Seagate Barracuda 3TB (No cache) 13.3 minutes
Seagate Barracuda 3TB (Maximize Cache) 13.3 minutes
OCZ Vertex 3 240GB (6Gbps) 5.5 minutes

A pure SSD setup is going to give you predictable performance across the board regardless of what you do, whereas Intel's SRT is more useful in improving performance in more limited, repetitive usage models. Admittedly most users probably fall into the latter category.

In my use I've only noticed two reliability issues with Intel's SRT. The first issue was with an early BIOS/driver combination where I rebooted my system (SSD cache was set to maximized) and my bootloader had disappeared. The other issue was a corrupt portion of my Portal 2 install, which only appeared after I disabled by SSD cache. I haven't been able to replicate either issue and I can't say for sure that they are even caused by SRT, but I felt compelled to report them nevertheless. As with any new technology, I'd approach SRT with caution—and lots of backups.

 

Application & Game Launch Performance: Virtually Indistinguishable from an SSD AnandTech Storage Bench 2011 - Heavy Workload
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  • µBits - Monday, July 11, 2011 - link

    http://download.intel.com/support/motherboards/des...

    System Requirements:
    For a system to support Intel Smart Response Technology it must have the following:
    • Intel® Z68 Express Chipset-based desktop board
    • Intel® Core™ Processor in the LGA 1155 package
    • System BIOS with SATA mode set to RAID
    • Intel Rapid Storage Technology software 10.5 version release or later
    • Single Hard Disk Drive (HDD) or multiple HDD’s in a single RAID volume
    • Solid State Drive (SSD) with a minimum capacity of 18.6GB
    • Operating system: Microsoft Windows Vista 32-bit Edition and 64-bit Edition, Microsoft Windows 7 32-bit Edition and 64-bit
    Reply
  • codedivine - Wednesday, May 11, 2011 - link

    I am interested in using Linux and I am wondering about various things:
    1. Will it work under Linux? Can I configure it from Linux?
    2. Is it file system dependant? I guess it is not.
    3. Whether it will work on multi-OS machines. For example, what happens if I dual boot Windows and Linux?

    Unrelated to Linux is, does this scheme get confused by say using lots of VMs?
    Reply
  • Penti - Wednesday, May 11, 2011 - link

    No, so called fake raid (software raid) that the chipset/drivers supports do never work in Linux. RST do not work under other OS's then Windows. Mac and Linux will have to use the built in software raid rather then the none existing driversbased one. And will lack all support for SSD caching.

    VMs usually write to a virtual hard drive (file) that saves the data to the disk. That should be absolutely fine.
    Reply
  • Mulberry - Saturday, May 21, 2011 - link

    but to the question on dual booting:

    Can you dual boot eg. Win XP and Win 7?
    Reply
  • headhunter00 - Sunday, August 07, 2011 - link

    well, you can always set the root partition on the ssd, by creating custom partitions during installation, and set the resource hogging partitions such as /var and /home on your hdd. this way, all the binaries and libraries load from the hdd. if you don't have enough space on your hdd to do that either, then you are out of luck. thats the closest you can get to ssd caching in linux. ofcourse there is a patch for the kernel to do ssd caching natively, but its pretty outdated and probably not compatible with your hardware. to do ssd-caching in windows with linux, you have to preserve some space on ssd to do so. Reply
  • MonkeyPaw - Wednesday, May 11, 2011 - link

    The virtue interface is awful. Looks like the ugly tree fell on that android girl. Reply
  • sunbear - Wednesday, May 11, 2011 - link

    Consumer nases (readynas, qnap, etc) could really benefit from this. Flashcache (http://planet.admon.org/flashcache-caching-data-in... released by facebook also looks interesting. Reply
  • fitten - Wednesday, May 11, 2011 - link

    Can you have an SSD as your boot drive, then a large HDD (typical configuration... OS/apps on SSD, data/etc on HDD) and then have yet-another SSD enabled with SRT for caching the HDD? Seems like the best of both worlds (other than cost). Reply
  • swhitton - Wednesday, May 11, 2011 - link

    I reckon that setup would almost certainly work fine.

    What I'm wondering is whether you could use a single SSD partitioned so that part of it was a boot drive and the other part was a cache for a HDD. Such a setup would solve the problem of the 120gb SSD not being quite the right size for any particular purpose.

    A 60-80gb partition with Windows and apps on it and the remaining space used as a cache. This would avoid the problem of having to symbolic link Steam games and so forth, while also not requiring you to buy two SSDs in order to have a boot drive and a cache drive.

    Anand did mention that a cache drive could be partitioned so that only part of it needed to be used as a cache. Just not sure if there would be any issues that might arise with using the remaining partition as a boot drive.

    Thoughts anyone?
    Reply
  • y2kBug - Wednesday, May 11, 2011 - link

    Here is a quote from vr-zone.com’s review (http://vr-zone.com/articles/first-look-msi-z68a-gd... ) on SRT: “All existing partitions on the SSD must be deleted before it can be used as a cache”. This makes me believe that using oneSSD for dual purposes (boot drive and SRT at the same time) is not possible. I really want to hear Anand’s last word on this. Reply

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