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All You Need to Know About UASP


What is USB attached SCSI or UASP?

We have all experienced a profound paradigm shift in how various forms of content is now being created, made digitally available, and shared. We are capturing more and more of our lives today in a digital form.The challenge is not only to create and capture this content, but to aggregate, analyze, store, and share this copious amounts of data, both locally and globally. As this trend continues and technology improves, the quantity of data and the size of it continue to grow exponentially, the data needs to be stored and backed up. And so we all back up our data, right?

USB technology has improved a lot in the past 10 years, making it possible to transfer and backup bulk amounts of files faster than ever before. USB 3.0 currently supports speeds of up to 5.0 Gbps of bi-directional bandwidth. Next, in this natural progression is the USB 3.1 with a whopping 10Gpbs bandwidth.

The mainstay of mass storage for both USB 1.1 and USB 2.0 has been the Bulk-Only Transport (BOT) standard. This served the computing industry well with its modesty in affordability, efficiency, and simplicity. However, for some, this speed is not enough due to the sheer volume of data that require backing up. Good examples are pictures, videos or if you are an enterprise/business user, server and computer image backups. This is where UASP can be of great assistance to you.

What is UASP?

UASP stands for USB Attached SCSI Protocol. It allows for faster read/write data speeds to and from storage devices.

Compared to traditional USB 3.0 BOT, UASP performs up to 70% faster read speeds and 40% faster write speeds at peak performance.

This is made possible due to the way UASP functions in comparison to USB BOT. UASP processes transfers in parallel, delivering data signals (Commands, Status, and Data In & Out) in dedicated “pipes”. BOT on the other hand, requires each signal to travel on the same “pipe”, taking turns, thus slowing the file transfer process.

Another benefit to UASP is the reduction of required processor resources used by traditional USB when transferring data. At the same peak in testing, UASP shows an up to 80% savings in processor resources.

How do I know if I have UASP?

To take advantage of UASP-enabled devices you will need to be running Windows 8 or newer, or Mac OS X 10.8 or newer. Some versions of Linux running kernel 2.6.3 and higher can take advantage of UASP, but it is limited to a very small set of supported hardware.

Most USB 3.0 hard drive enclosures and docking stations support UASP. All supported UASP hard drives docks and enclosures include UASP in the product title as well as the technical specifications section.  And with the new USB 3.1 Gen 1 (5 Gbps) and USB 3.1 Gen 2 (10 Gbps) enclosures for 3.5” SATA drives, you will be able to get the speed and capacity you want in external data storage. Our single-drive enclosure for 3.5” SATA hard drives gives you Super-Speed Plus USB 3.1 Gen 2 (10 Gbps) performance with a large drive capacity of up to 6TB – twice the speed of Super-Speed USB 3.0 (USB 3.1 Gen 1) technology. It lets you leverage the high performance of the latest SSHDs and hard drives while alleviating bottlenecks in your data transfers.

Having a supported Operating System and hard drive enclosure/dock are not the only requirements for taking advantage of UASP. Your USB controller on your computer also needs to support UASP. Like enclosures and docks, most controller cards, including ones, are UASP supported but be sure to check the specifications before purchasing a new card.

Taking advantage of UASP will save you a lot of time when transferring large amounts data, enhance your PC’s performance and free you up sooner to get back to the daily grind.

Check out our lineup of UASP supported products:

UASP External Hard Drive Enclosures

UASP USB 3.0 Controller Cards

**We have been working hard to enable TRIM as a standard feature and offer firmware solutions for our newly released storage products but at this moment it is not fully supported with all products. We have a solution currently available for all of the enclosures listed below, and we are working to release a field upgradable version for our other USB 3.1 Gen 2 products. products that support TRIM.


If you have any questions regarding this issue, our Tech Support is always available to answer your questions: 


  1. Kurian Abraham 5 years ago

    Do your UASP enclosures support translating the SCSI UNMAP command to TRIM? Otherwise SSDs in the enclosures won’t receive TRIM commands.

    • Susan Mutterback 5 years ago

      Hi Kurian,
      Yes, all of our single bay enclosures support TRIM commands. If there is a particular product you are interested in knowing more about, we would be happy to look into it. Thanks!

      • Kurian Abraham 5 years ago

        I have this particular one which uses the ASMedia ASM1351 USB to SATA bridge:

        I believe the ASM1351 chipset does not support UNMAP to TRIM command mapping at all. Look at this post that tests the TRIM capability of USB enclosures:

        • Susan Mutterback 5 years ago

          We looked into this further for you and discovered a some commands are not being passed on to the drive. If you like, we can arrange for firmware that will enable the functions you need. Let me know and I can email you directly to get you the proper firmware. Thanks!

          • Tom Yan 5 years ago

            I’ve got the aforementioned adapter as well. Could you email me the firmware with UNMAP support? It would be best if you could also email me the original firmware without the support enabled, just in case the feature does not work well.

          • Susan Mutterback 5 years ago

            Hi Tom, I’ll look into this as well for you!

          • Susan Mutterback 5 years ago

            Hi Tom,
            Our Tech Support team will be able to help you with the update. Please contact them:

      • Dominic 5 years ago

        I used a trim check tool to see if my ASMedia 2115 was trimming my mSATA 840 EVO and it was not. I bought an mSATA to SATA III adapter and I trim my SSDs every once in a while

  2. Manzur Fahim 5 years ago

    Hello Susan,

    I have the same adapter USB312SAT3CB and also USB31CSAT3CB. And they also do not have TRIM support. Would it be possible to have a firmware upgrade for the adapters so I can have TRIM support. I use many SSDs with these adapters and they are slowing down as TRIM as it is isn’t working.

    Many thanks.

    • Susan Mutterback 5 years ago

      Hi Manzur, I’ll look into this for you!

    • Susan Mutterback 5 years ago

      Hi Manzur,
      Our Tech Support team will be able to help you with the update. Please contact them:

  3. Steve 5 years ago

    I had an Acer R11 convertible notebook and I used this with four different UASP enclosures containing a Samsung SSD on the USB 3 ports. I had lots of problems with all four enclosures both under Windows 8 and 10 (hanging, corrupted filesystem ,ect.) and when booting directly from the USB drive via the BIOS. I had no problem on other systems. So the Acer R11 clearly has some ‘issues’ with USB 3.
    I have 2 Q’s
    1. Is it likely that the BIOS/firmware would use UASP when booting from the USB 3 enclosures?
    2. If I connect the USB 3 enclosure to the USB 3 port on the laptop using a USB 2 extension cable – will it still use UASP or is that a USB 3 feature only?

    • Susan Mutterback 5 years ago

      Hi Steve, Are you using products? If so, we would be able to provide more in-depth information but I have some answers to your questions below.

      1. This is possible and could be confirmed with your motherboard manufacturer.
      2. UAS and UASP were introduced as part of the USB 3.0 standard, but can also be used with devices complying with the slower USB 2.0 standard, assuming the cable supports it.

      Let us know if you have any other questions.


  4. Ramon 5 years ago

    Hi Susan,

    I would like to know if the following products could support TRIM if I would buy them at this time

    Kind regards,


    • Susan Mutterback 5 years ago

      Hi Ramon,

      Unfortunately, the products you listed do not have TRIM. We are still working on the auto/self-installer for the S251BMU313 and the firmware to enable TRIM for the S2510BMU33CB. Please contact our technical support team if you have any other questions:


  5. Rob E 5 years ago

    Hi Susan.
    Can you please tell me if either of these enclosures currently support TRIM and SMART attribute passthrough:
    Thanks, Rob

  6. Eduard 5 years ago

    Hi Susan,
    Does this enclosure support TRIM or it will be soon with a firmware update?

    • Eduard 5 years ago

      Sorry, I forgot the enclosure name… S251BPU313
      Thanks again!

  7. Jason 5 years ago

    I have just brought the S251BMU313 but found that it doesn’t support trim.
    I see the posts that you have been working on the firmware update.
    What is the progress so far? Will it be available soon?
    I’m considering to return it before the returning window closes.

    • Susan Mutterback 5 years ago

      Hi Jason,

      Check in with our Technical Support team, they will have the most up-to-date status on the firmware: They can help you figure it out or help you return it if you need to.

      Our Support team is available via chat, email or phone (and are available 24×5, Sunday 9pm to Friday 9pm (ET)).


  8. JLum 5 years ago

    I was on chat about this and they said this S251BMU313 was being worked on but no ETA. I’ll put in my vote for updating it to support Trim (I have a S251BMU313 and am trying to decide to hold until new firmware or return it) because of the Trim+SSD problem.

  9. Paolo 5 years ago

    Hi Susan, i was wondering if startech offers a usb3.1 to SATA adapter that is not fully vulcanized into rubber, but that can be opened.
    I’m asking this because i experience severe faults with usb3 to sata adapters due to the bridge chip insanely overheating.
    I’m looking for something simpler than the akitio neutrino, just sata to usb3.1, but not in a fully vulcanized cable, or in an enclosure that can’t be dismounted


    • Susan Mutterback 5 years ago

      Hi Paolo,

      If you are looking for a product suggestion or have questions about our products, please get in touch with our Technical Support Team. They would more than happy to help you out!


  10. peter 5 years ago

    hi susan. Any update for trim support on s251bmu313? I emailed, but they couldn’t provide any update. I am curious though, as it has the same chipset as other external enclosures that you have enabled trim but not for this one which also happens to be one of the most expensive you have for 2.5 inch.

    • Rob 5 years ago

      I’m also disappointed by the omission of TRIM support for the aluminum version of the USB 3.1 enclosure (as listed in the FAQ linked below). So the choice seems to be either settling for plastic or buying an enclosure from another manufacturer.

  11. john 5 years ago

    Observed Standards, you guys might be able to explain whats going on.
    What I have seen is that if you use a Sata drive in one dock, it can appear to not be formatted in another dock.

    For example i have 1 dock which supports firewire 800 and usb2 this is ideal for my mac’s as firewire800 is at least twice the speed of USB2. Now if i want to read that drive on another computer with USB3 and not firewire If i put the drive in a USB3 compatible dock then the drive format isn’t recognised. Ok if it is returned to the first dock.

    So it seems there is a difference in the way that the 2 docks communicate with a SATA drive. Is it just a protocol issue or is it worse than that. If it is a matter of protocol how do i figure out which protocol is being used by which dock. Naturally I would prefer to find a USB Dock that is compatible with drives that have been formatted in the Firewire Dock.

    If anybody knows, it has to be you guys, thank you

  12. Robert 5 years ago

    This blog post is high in google results for people interested in whether StarTech enclosures support ATA TRIM to SCSI UNMAP translation, and I suggest you take advantage of it. Right now, most external USB 3.0 enclosures with UASP support still don’t do ATA TRIM to SCSI UNMAP translation, so you have an opportunity to stand out in the market. Just having this page being so visible is a nice start, but the main question still isn’t answered here after all of this time.

    Rather than individually redirect people offline to your tech support team (where who knows what happens and if anything gets resolved), why not openly help everyone else who finds this page by simply publishing a list of your current USB enclosures with UASP support that do ATA TRIM to SCSI UNMAP translation? This is an important stand-out feature, and finding solid information is still annoyingly difficult at the moment.

    Thanks in advance!

    • Susan Mutterback 5 years ago

      Hi Robert,

      We now have all of our products that support TRIM listed here:

      • R00KIE 4 years ago

        I believe that what Robert was talking about is something more specific than just having trim work under windows, which as far as I can tell (from searching google) uses ata passthrough to issue trim commands.

        What Robert would like, and I would also be interested in is having the controller map SCSI UNMAP to ATA TRIM, which would in theory allow current linux versions to issue trim commands to an ssd inside the enclosure.

        I own a S251BPU313 enclosure, trim does work under windows but fails on linux. I agree with Robert that if trim worked well both on windows and linux it would be a differentiating feature and might be the deciding factor of buying one of your enclosures.

  13. cat1092 5 years ago

    What about that very popular (& often on promo) SATA to USB adaptor with cable I use to clone/backup drives with, usually around $10 to $13? As long as I’m using WinPE media (Windows 8.1 or 10) created by Macrium Reflect, shouldn’t the USAP function still work, even if using to image an XP/7 partition or drive, since it’s running outside of the Windows environment?

    I have two of these & performs backups faster than my USB 3.0 docking station, as well as my eSATA to USB cable, the latter of which is used mainly for the secure erasing of SSD’s.

    • Susan Mutterback 5 years ago


      Our Technical Support will be able to explain the technicalities and if the UASP would still work in your setup. They are available via chat, phone or email.

  14. Herbert 4 years ago

    Hi there,
    TRIM is important, what about power save features? Will USB attached storage allow DIPM (SATA Device Initiated Power Management), HIPM (HOST Initiated Power Management) and LPM (SATA Link Power Management)?

  15. Jim 4 years ago

    I’ve Googled this to no avail: how do I disconnect an external USB hard drive (either UASP or not)? Do I simply “hot unplug it” so to say, when the drive still possibly spins? there is no eject button for USB hard drives such as for USB flash drives. It’s confusing and does not feel right. Thanks!

  16. Anonymous 4 years ago

    Is there such a thing as an mSATA enclosure with UASP? One “answer” I saw made it seem like these were like oil and water (that is, not to be blended together) but other (M.2, 2.5″ SSD) enclosures both should and do have UASP.

  17. Raffaele 4 years ago

    Hello, is there any update on TRIM support for the S251BMU313 USB 3.1 enclosure? I ended up on this page while searching and I read that you were working on something for that.

    • Barry Weston 4 years ago

      Hello Raffaelle,

      Thanks for getting in touch.

      We have updated this device to support TRIM. Please head over to to get in touch with one of our advisors (phone or live chat) and they will assist with replacing your enclosure with an updated TRIM ready version.

  18. Anom 3 years ago

    Do you have a list, where we can look which products will support all those needed commands (TRIM and others)?

  19. Kevin 2 years ago

    I have this adapter:

    I tried to update the firmware by running this:
    (I’m on windows 7 x64. An ssd was connected through the adapter.)

    I then ran trim check:

    which reported that trim was not working.

    Am I missing something. Please advise!

    • Danielle 2 years ago

      Hi Kevin!

      While TRIM support is listed on our tech specs for our USB312SAT3CB adapter cable, it also needs to be enabled on the SSD that you’re using. Our team will need to know the makes & models of your drives to confirm if TRIM support is enabled. They’ll be able to help you troubleshoot via live chat ( or phone: 1-800-265-1844.

      We hope that helps!

  20. 2 years ago

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    Please ⅼeet mе know if this ok wth you. Thankѕ!

    • Danielle 2 years ago

      Hi there! We’re glad our articles are providing you with information that interests you. As long as you source/link back to our articles, we’d be happy for you to share the content you find beneficial!

  21. jere burbank 2 years ago

    will this work with windows 10?

    • Danielle 2 years ago

      Thanks for your interest in our products. UASP is a protocol built into USB technology and is supported in most modern operating systems including Windows 10. If you have questions about a specific product’s compatibility we’d be happy to help you further. Feel free to contact us at where our Technical Advisors are available 24 hours a day, Monday to Friday.

  22. Doug 8 months ago

    What about your SD card readers? A TRIM-like function is available in the SD spec, and I would guess that UASP-based devices could support it. But there are no SD card readers listed in your TRIM-support devices link.

    • Danielle at 8 months ago

      Hi Doug! Unfortunately, none of our current SD Card readers are specifically designed to support TRIM.


  1. […] from another location near to 540 MB/s, your computer system has to support USB 3.1 Gen 2 and have UASP mode (which makes it possible for quicker information read/write speeds) […]

  2. […] sides of the USB connection as well as the operating system (Linux 3.15, Windows 8 or OS X 10.8). StarTech claims that read and write performances can be up to 70% and 40% faster respectively, with a significant […]

  3. […] USB 3.0 with UASP protocol for enhanced read speeds, and is compatible with 2.5inch SATA III drives which can be installed […]

  4. […] with Windows OS, Linux, and Mac OS. You just make sure any device you want to use it supports the UASP […]

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