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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  • jordanclock - Wednesday, May 11, 2011 - link

    You can use a drive for both, but you must set up your data partition AFTER you set up the cache partition. Reply
  • jorkolino - Wednesday, June 06, 2012 - link

    What do you mean by that? You partition the SSD drive, install the OS in the first partition, set-up the other partition as a cache, and then format your remaining HDD? Reply
  • jorkolino - Wednesday, June 06, 2012 - link

    I wonder, can you tell SRT to cache blocks only from the HDD onto the cache partition, because by default SRT may decide to cache system files that already reside onto a fast SSD partition... Reply
  • evilspoons - Wednesday, May 11, 2011 - link

    I know it's early on for Z68, but I'm curious how other SSDs will perform in SRT mode. I ask because the 40 GB X25-V is on sale here for half its usual price... Reply
  • evilspoons - Wednesday, May 11, 2011 - link

    To answer my own question, Tom's Hardware reviewed SRT with several SSDs and to put it bluntly, the X25-V sucks. Its very low write speed of 35 mb/sec actually drags the hard drive down in a few tests. Reply
  • Shadowmaster625 - Wednesday, May 11, 2011 - link

    Yeah that is a nice way of putting it. Talk about sugar coating. Here is a question for ya: was intel being "conservative" when they tried to shove rambus down everyone's throats? If it werent for AMD and DDR god knows how much memory would cost now. I still have one of those rambus P4 systems running in the lab right now. (intel 850 chipset with dual channel RDRAM). I did some memory benchmarking on it and was shocked to find that it was actually slower than any of the P4 DDR 266 machines we have running. (Yes we are slow to upgrade lol.) It runs at about DDR200 equivalent speeds. And we really paid out the wazoo for that system. Reply
  • Shinobisan - Wednesday, May 11, 2011 - link

    discrete graphics cards are limited - even though they often have three, four.. or more connectors these days, they can often only drive two monitors at a time. (unless you use a displayport connector... and monitors with DP don't really exist yet)
    I have two monitors driven by my HD6950 via the digital video out connectors. So the HDMI connector on that card is "dead" until I turn one of the monitors off.
    What I would like to be able to do... is have my dGPU drive my two monitors, and the iGPU drive my 1080p TV via HDMI.
    Can I do that? This discussion on virtu muddies the water some. unclear.
    Reply
  • Conficio - Wednesday, May 11, 2011 - link

    Well, so SRT is a good idea but again it is limited artificially in its use. Sounds to me like the P67/H67 stund all over again.

    Why is it limited?
    * For starters it is driver supported, and I believe that means Windows only (I could find no mention of what OS is supported). To be fully useful it belongs into the chipset/BIOS realm.
    * Next there is the artificial 64GB limit. As is obvious from even the tests that is not really the practical limit of its usefulness. It is simply a marketing limit to not compete with Intels own full SSD business. You got to ask yourself, why not use your aging SSD of 100GB or 256 GB (a couple years down the road) as an SRT drive?
    * "With the Z68 SATA controllers set to RAID (SRT won't work in AHCI or IDE modes) just install Windows 7 on your hard drive like you normally would." So only RAID setups are supported? Well you are testing with a single hard drive, so this might be a confusing statement. But if it is RAID only then that is ceratinly not what Joe Shmoe has in its desktop (let alone in its Laptop).
    Reply
  • A5 - Wednesday, May 11, 2011 - link

    If the AT Heavy Workload Storage Bench is a typical usage case for you, than you shouldn't be using SRT anyway - you'd have a RAID array of SSDs to maximize your performance. Reply
  • jordanclock - Wednesday, May 11, 2011 - link

    For caching purposes, I'm sure 64GB is a very reasonable limit. The more data you cache, the more data you have to pay attention to when it comes to kicking out old data.

    And it isn't a RAID set up, per se. You set the motherboard to RAID, but the entire system is handled in software. So Joe Shmoe wouldn't even have to know what a RAID is, though I don't see Joe Shmoe even knowing what a SSD is...
    Reply

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