back to article Cache 'n' carry: What's the best config for your SSD?

The idea of using a low-capacity SSD to store the most frequently accessed files or parts of files in order to access them more quickly than a mechanical hard drive can serve them up - a technique called SSD caching - has been around for some time, but it wasn’t until the arrival of Intel’s Smart Response Technology with the …


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  1. jason 7

    So the lesson here is....

    ...just buy the Sandisk Extreme? That it?

    Well It's what I've done already.

  2. Richard Lloyd

    Not a single mention of Linux anywhere

    Sad to see that Linux isn't mentioned (or indeed benchmarked) here, even if it's just to suggest what the equivalent of Intel's SRT is for Linux. If you're building a new machine, I'd expect it to have SATA 3 because SATA 3 SSD prices are continuing to fall.

    The only sensible combo, IMHO, is a Sata 3 SSD with 500MB+/sec read/write and a fast multi-terabyte HDD (I use Seagate 3TB's myself at 225Mbytes/sec read). Throw in a fast multi-core CPU and you're not far off 10 seconds boot time, meaning that multi-boot isn't tiresome any more.

  3. Dave 126 Silver badge

    Re: Not a single mention of Linux anywhere

    ZFS can do this sort of thing (RAM > RAM disk > SSD > HDD), but I don't know its state of play with respect to Linux

  4. Anonymous Coward
    Anonymous Coward

    Re: Not a single mention of Linux anywhere

    ZFS is available via fuse, been using it for years.

  5. Bronek Kozicki Silver badge

    you forgot ...

    LSI CacheCade

  6. Inspector71
    Thumb Up

    Make your Own

    As far as the Fusion Drive is concerned. All the tools for rolling your own are built into the file systems in Lion and Mountain Lion. I built one for my Mac Pro ( which is only SATA 2 ) with a 256GB SSD and a 2TB WD Black. Very nice increase in performance and drops you straight into login after about 10-15 secs.


    Re: Make your Own

    I'm running an intel S3700 200GB SSD with a 2TB WD Red, setup as a Fusion drive in this late '09 iMac. It makes a huge improvement in speed and boots ~5 seconds after the logo. The SDD replaces the optical drive, which only has a SATA II interface on the MoBo.

    A month prior to the 'S3700 I installed an OCZ Vertex 4 - it was a disaster..... The OCZ was fast, but couldn't cope (at all) with our regular power outages. We're in the country and we're lucky if we can go for a week without copping an outage. Even after a re-install with a non-Fusion setup, with the SSD configured as the boot drive, after one outage the SSD completely lost its brain and the machine wouldn't boot! This is a machine that has survived countless power outages over its >3 year life (configured with a HD) with no known data corruption...

    Yes, a UPS would help, and I'm repairing some very nice sine-wave units rescued from a dumpster, but the OCZ SSD was so flaky that I couldn't risk kicking the power cord - I expect I'd lose data or down time (it's a business machine). Yes, it is backed up on the hour.

    I had a play with ZFS ( but it doesn't support time-machine and the can't boot from ZFS.

    My theory re OCZ power outage flakiness is that the relatively large RAM caches required in all SSDs (to extend service life and improve performance), combined with background wear-leveling and pretty ordinary firmware, means they're very susceptible to (unexpected) power loss. They probably fare much better in laptops than desktops, as the lappy battery provide a UPS-like function.

    It seems only the enterprise grade drives are designed to properly cope with power loss; they all have some form of hold-up capacitance, with power loss detection, to give the on-board controller enough time and energy to dump the RAM contents to flash, so they can recover gracefully next power on. The cost of the capacitors and associated circuitry is quite low. IMHO all >2.5" form factor drives with enough room for the circuitry.

    The model new iMac (with the damn screen held on with tape - ARGGHHHH) can be order with SSDs (Sammy 830 series apparently). Assuming these consumer level SSDs don't have on-board capacitors, it may be the MoBo, power supply and firmware support some form of early power-fail detect to allow orderly power-down of the SSD. If not, I can't see these imacs being too reliable..

    I realise the 'S700 may sound like complete overkill given the price, but it claims to have consistent performance (see and a good life expectancy, so I expect to able to transfer it to a new machine in a couple of years.

    FYI: After the OCA nonsense, I've hammered the intel SSD configuration; intentionally pulled the power numerous times and saw no data corruption whatsoever, well, according to disk util and the general imac happiness..

  8. onefastskater

    Re: Make your Own

    I had to purchase a 15" MacBook Pro before the latest refresh that included retina displays, my old one died. Initially I was upset, yet lucky me the new MacBooks are not easily modified. I replaced the 750GB 5400rpm drive with a 7200rpm drive. I removed the DVD drive and replaced it with a 512GB SSD. I used the diskutil core storage commands to bind them into a volume and the machine is really fast. Someone mentioned a 12-15 second boot time and I regularly get 12-13 second boot up form a cold start. ~8 seconds of that is hardware check. I fly a lot and not only is the machine faster, but the battery life is extended because I'm not spinning a drive all the time. Would like to have the ability to pin a file on the SSD.

  9. Alex Walsh

    Sandisk Extreme

    Where can I get one of these for around £75 then? Best I've found is £89 :)

  10. jason 7

    Re: Sandisk Extreme

    Ebuyer have them for £85.

    I have bought half a dozen of the Sandisks (Ultras and Extremes) all of them have worked fine.

  11. Nigel 11

    Missing - hybrid drive?

    I'd really have liked to see that review also compare a hybrid drive such as Seagate Momentus. Yes, it's a slow sleepy 2.5 inch laptop drive, but how much difference does that built-in flash cache make? And being out past the drive end of the SATA connector, it'll work with Linux or anything else you care to boot.

    With Linux it is trivially easy to put the operating system and your own small / heavily accessed files onto a small SSD. One can configure a completely useful Linux system in 30Gb (about 15Gb of system files, 15Gb /home). Unfortunately 30Gb SSDs are slower than 256Gb ones, but they share the same near-zero seek time. Again it would be nice to see that benchmarked.

  12. jason 7

    Re: Missing - hybrid drive?

    Yes its all in the access times really. Once you get over 150MBps with near instant access times then application opening etc. becomes moot.

  13. Matthew 17

    Re: Missing - hybrid drive?

    I have one of these, they're not slow, 7200RPM, large cache + 8GB of SSD.

    I love mine, they're made a huge difference to my MBP and still gives me 750GB of storage to play with. As the caching is at the block level it's invisible to the OS and there's no messing about having to decide what is cached and what isn't.

    You notice the difference when you install a service pack or new OS as the next couple of reboots are much slower as it updates the cache and the speed returns.

    The only thing I don't like about it is that there is supposed to be quite a difference performance-wise depending upon what firmware is installed on the drive, however there are no tools I've seen for OSX that enables the user to upgrade.

  14. DrAJS

    Re: Missing - hybrid drive?

    I've got the 4GB/500GB Momentus XT hybrid drive in my laptop and it transformed it. Before (500GB, 5400rpm HDD) startup took 2mins 20 secs. Now I can do a full restart in 26 secs... and I've still got 500GB of storage. Very much the best of both worlds.

    Vaio S, i5-2410, 4GB RAM.

  15. Captain Scarlet Silver badge
    Thumb Up

    Corsair Accelerator owner and Hybrid for lappie

    Love these products but the Dataplex software isnt 100% perfect, Windows updates and even upgrading Eset Nod 32 to the latest version meant it would sit at the Windows booting screen. So had to disable it and suffered the horror of slow booting and reinstalling the software (Come on Dataplex give me an easier way to re-enable caching over than uninstalling and reinstalling the software).

    The seagate hybrid is in a lappie has been spot on boots quickly and means it should last a few more years.

  16. Turtle_Fan

    Enquiring minds would like to know...

    Why is it that in all SSD-related discussions, PCI-E based versions are never mentioned.

    From what I could see (and have been using) PCI-E based SSD's tend to have the best performance compared to SATA III (6 Gbps) and due to the slot, they can accommodate sizeable capacities without any space limitations.

    And yet, reading the reg you'd think they don't yet exist.

    (It's not for lack of demo units, is it?)

  17. Chris Beach

    Re: Enquiring minds would like to know...

    urm cost probly! PCI-E are still in the realms of fantasy/extreme enterprise usage, for a typical consumer they aren't even close to being a viable option. Even if the cost came down the installation/usage isn't as straightforward either.

    Plus they are no use at all for laptops.

    tbh they are temporary stopgap until the next SATA protocol appears and fixes the 6Gb bandwidth limit. (SATA Express is the current forerunner)

  18. Steve Davies 3 Silver badge

    Re: Enquiring minds would like to know...

    simple really

    They are too frigging expensive when compared to SATA drives.

  19. Alan Brown Silver badge

    Re: Enquiring minds would like to know...

    "Why is it that in all SSD-related discussions, PCI-E based versions are never mentioned"

    Because they tend to be bloody expensive.

    Thumb Up

    Great stuff

    This review is both timely and relevant to me. I just powered up a new 3k USD machine last night. I put 256G SSD as the OS. The 'G' drive is a 128G SSD with a 1TB Seagate Black drive connected to the Marvell chipset that came on the ASUS P8Z77-V deluxe.

    It takes about 15 seconds to cold boot. The performance on Folding@home equals all the personal computing power of the previous 10 years running in 24 hours. Just amazing.

    So far I did a standard format on the 1TB 'G' drive and two standard 1TB drives but have yet to compare the performance. My plan is to install large programs to the 'G' drive. This writeup sure saves me the time in research, so thank you. I don't think the Marvell chipset has the same performance as the Intel but it is surely better than a plain old spinning drive.

  21. Joerg

    The best SSD config is SAS RAID controllers with SSD as cache

    Expensive ? Indeed.

    Needed ? Indeed.

    Whoever can afford buying such configurations absolutely should for getting maximum reliability and maximum performance.

    Adaptec Series 7Q with maxCache 3.0

    71605Q: 16 internal ports

    - caching writes to a redundant SSD cache pool (either RAID1E or RAID5)

    - Supports up to 8 SSDs with up to 2TB of SSD

    So a 12 SATA Enterprise class 1TB or 2TB hard disk drives in RAID-5 with 4 256MB SSD MLC as cache would give top-notch sustainted performance and good reliability with that controller. It means well above 1GByte/s both read and write with a such a config.

    Eight internal SATA+SAS ports

    SSD-Optimized Software included; CacheCade Pro 2.0 and Fast Path Ready

    MegaRAID® CacheVault flash cache protection (included)

    A $300-$400 SAS expander needs to be added for getting more than the 8 included ports. The LSI is more expensive anyway than the Adaptec but it's way faster. With a 12 SATA Enterprise class 1TB or 2TB hard disk drives in RAID-5 with 4 256MB SSD MLC as cache config the overall speed could go well beyond 1.5GByte/s

  22. Turtle_Fan

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    Save yourself all this complexity and cost.

    A good OCZ Z-Drive v4 is all you need: 2.8 GBps sounds like more than enough even for your needs.

    Screw shopping around, assembling, setting up and fine-tuning. Since money is no obstacle for you, slap one of these beauties on and away you go.

  23. Joerg

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    You have no clue what you are talking about.

    A single SSD is not reliable, way worse than a single hard disk.

    Reliability and fast performance must be both achieved for anyone that cares about protecting data either being a business or an average user.

    RAID configurations are needed to achieve that.

  24. Turtle_Fan

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    I don't know if you're being silly or purposefuly negative for no reason.

    Let's see...

    RAID: What do you think is the array on the OCZ if not a RAID array of user replace-able flash memory modules?

    LSI: What do you think binds everything together and keeps it going? An LSI SAS controller on top of everything.

    And if you cared to look at the specs you'd see that there's anything from 15% to 30% overprovision of flash versus the nominal capacity.

    So under which scenario is your combo any more resilient than the OCZ? If the controller card goes you're in trouble just as you'd be with OCZ (the data still gets preserved in both cases). If any of the disks packed up then you'd have resilience just as you'd have on the OCZ (well up to a point in both cases).

    And btw, I mention OCZ just as an example, I'm sure that there are other suppliers of similar kit.

    So, if anything, don't be so hasty with personal attacks :)

  25. Joerg

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    You are the silly one here that clearly doesn't have a clue what he is talking about.

    You clearly don't know know how RAID controllers work either.

    And no, if a controller fails you don't lose all your data, changing the controller with a new one getting back all the data is not only possible but it quite rarely happens in data centers.

  26. Bronek Kozicki Silver badge

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    FWIW, I use MegaRAID with few SSDs in RAID0 configuration and FastPath (I like it fast). Am I being careless with my data? Not really, I run backups every few hours apart, onto HDD, also rsynced to external machine. Few hours potential loss of data is not much of a problem for me. However, I might consider switching to CacheCade since I also have few unused 2TB drives. Would need to attach Chenbro or similar expander first, too lazy for it ATM ;)

  27. Turtle_Fan

    Re: The best SSD config is SAS RAID controllers with SSD as cache

    Oh learn to read man.

    Where did I ever say that a controller failure results in data loss?

    And spare the storage101 lecture for those who need it.

  28. ncbill

    No need for any cache - just go pure SSD

    Already, 512GB SSDs have dropped to around US$300 (Samsung 840, street price)

    Shave at least another US$100 off the above by Xmas.

    Just wait a bit and buy one SSD, forget the traditional rotating hard drive for most of us.

  29. Joerg

    Re: No need for any cache - just go pure SSD

    And a 512GB SSD would be enough for what exactly ?

    Booting the OS maybe and just that.

    Nowadays a PC can't have less than 2TB.

    It's quite common having 6 or more 3.5" 2TB hard drives in a mid-tower or full-tower case.

    Try buying 12TB of SSD ... if you can afford that.

  30. jason 7

    Re: No need for any cache - just go pure SSD

    "And a 512GB SSD would be enough for what exactly ?

    Booting the OS maybe and just that blah blah blah."

    My goodness you build some shitty computers! I wouldnt ask you to run my IT dept!

  31. Joerg

    Re: No need for any cache - just go pure SSD

    Little kid you need to grow up and learn a lot of things before ever being able of even thinking about running an IT dept.

  32. jason 7

    Re: No need for any cache - just go pure SSD

    No your point was just totally over the top. Try a little less testosterone in your posts maybe?

  33. Alan Edwards

    Re: No need for any cache - just go pure SSD

    Nah, OSs aren't that big. I've got a 60Gb SSD (OCZ Vertex 2, if anyone cares...) as the boot drive in my PC, and there's still 25Gb left on it. There's also a 250Gb conventional drive for random junk, most of my data is on a 6Tb NAS.

    512Gb probably isn't enough if that's absolutely all you have, but it depends what you do with it. My mum survives on a 120Gb netbook.

  34. DRendar

    Re: No need for any cache - just go pure SSD

    "And a 512GB SSD would be enough for what exactly ?

    Booting the OS maybe and just that.

    Nowadays a PC can't have less than 2TB."

    The VAST majority of users don't need anything approaching 2TB - My Gaming machine for example has a 250Gig Samsumg 830, running Win7Pro, Libre Office, a few other apps, Steam and about a Dozen Games installed, and there's room to spare.

    Granted I'm not storing Gigs and gigs of Videos, and if I want to install a new game I need to install another, but where's the problem with that?

    The overwhelming majority of users run Windows with some antivirus, Office apps and everything else they do is through their browser - that would all fit in a 64Gig drive without any issues at all.

    And your comment about building 12TB of storage using SSDs only is argumentative and distinctly trollish. This article is about devices which are aimed at home/laptop use - no-one is suggesting using hybrid / cache drives for enterprise storage where 19" racks of dozens of disks are the norm.

    Go and crawl back under your bridge.

  35. KroSha

    Backup needed

    The one downside of a SSD is its lifespan. And once it goes, all the data is gone. Traditional platter recovery methods don't work and anyone who has a single SSD, perhaps in a laptop, has to have a regular backup strategy. Otherwise, one day, they are going to get a nasty shock.

  36. Steve Davies 3 Silver badge
    Thumb Up

    Re: Backup needed

    Totally agree with you there. I have a 480Gb OCZ SSD in my laptop. I run several Server 2008 VM's from it. Just recently, sleeping windows with some VM's open has resulted in the SSD drive not being mounted at system restart.

    So far hibernating the system seems to work but to be safe I have taken to closing down the VM's before travelling.

    I also backup said VM's to a 2TB USB3 drive every day. I take regular backups of the codebase I am working on and copy it to another USB3 drive.

    The speed difference that the SSD gives the VM's is huge. Booting an 8GB VM with SQLServer takes less than 10 seconds.

  37. jason 7

    Re: Backup needed

    Sleep mode and SSDs are a tricky mix. I tend to switch off most of those options when using SSDs.

  38. Stuart Halliday
    Thumb Up

    Be nice if my C: SSD would cache my image system thumbnail files off my USB Harddrive?

    This would speed up my opening of image directories...

  39. psychonaut

    Dont understand. Just buy a 64 or 128 gb ssd for system and docs and then if you need tonnes of storage for pics and music that wont benefit from being on the ssd use the existing massive sata disk you allready have as a slave. Total cost 80 quid.

  40. psychonaut

    And screw raid in non enterprise applications. Acronis or carbonite.

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