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SATA or USB 2.0 speed?

Discussion in 'Hardware' started by Denise_M, Jan 14, 2009.

  1. Denise_M

    Denise_M MajorGeek


    I'm thinking about purchasing a Dual Bay SATA to USB 2.0 (SATA I and II) JBOD External Enclosure that contains 2 SATA II ext hdds. The case has only a USB 2.0 port. Will the drives run as fast as SATA or the speed of USB 2.0?
  2. Senlis

    Senlis Staff Sergeant

    SATA II will be faster than USB by a clear margin. I have seen the specs and experienced the speed difference myself. Doesn't the external HDD have an external SATA port?
  3. Denise_M

    Denise_M MajorGeek

    No, just a USB 2.0 port. I don't understand the reasoning behind putting SATA drives inside a case that has only a USB 2.0 port.

    I know that SATA hdds are much faster than USB 2.0 but I don't know how fast they'll run when connected to a USB 2.0 port.
  4. Senlis

    Senlis Staff Sergeant

    It really depends on which SATA, but SATA 3Gb/s (sometimes referred to as SATA II) runs at 300 Mb/s.

    USB2.0 is 480 Mb/s

    By this it looks like USB2.0 is faster, but in reality SATA and Firewire is faster because of the way the technology is implemented.
  5. jlphlp

    jlphlp Master Sergeant

    Hi All,

    HD speed is mostly set by the speed that the drive can read or write from a buffer. The device used to load the buffer can be many times faster than the drive so may have little effect on the overall drive speed. Data is moved to the buffer in blocks. Maybe someone has tested such a thing and can add more to this.

    Good Luck, Jim
  6. Denise_M

    Denise_M MajorGeek

    You have me a little lost here. Isn't the buffer in the drive itself and has nothing to do with the case? If that's so, connecting SATA drives via a USB 2.0 connection (which is faster but slower "because of the way the technology is implemented" as Senlis mentioned), would only slow down SATA drives?
  7. aidan80

    aidan80 Private First Class

    With an external SATAII Hard Drive connected to a USB 2.0 controller you'd get the maximum theoretical transfer speeds. SATAII tops out at 300mb.. that's as good as it gets. There's some more room in USB 2.0 up to 480mb at burst rate but the SATA controller won't make use of it.

    A buffer is just a small, fast chunk of cache RAM for example on a CPU or in this case hard disk. The cache is normally small, used to be just a few dozen kb, now a few mb in size acts a temporary storage area for information moving from the disk to the systems main memory - CPU normally carried out by DMA.

    When selecting a hard drive the five things I look out for are:

    RPM Speed: typical is 7,200 (Faster can be better but hotter!)
    Buffer Size: e.g. 2MB (bigger is better)
    Interface Type: e.g. IDE, SATA/SATAII 3.0Gb/s and the older SCSI interface.
    Size Matters: Least with Hard Drives it does!.. My first was just a massive 1GB, how things have changed! A GB is no longer a GB!
    Price: Don't forget the price, more isn't always more and less isn't less.. read some reviews!
  8. jlphlp

    jlphlp Master Sergeant

    Hi Denise,

    Aidan's info should have cleared up any questions you have about data movement to a hard drive.

    Luck, Jim
  9. Denise_M

    Denise_M MajorGeek

    I believe what you're saying is that a SATA II drive inside a USB case can use it's full speed since the USB 2.0 speed is faster than SATA.

    Why do USB 2.0 ext hdds move data slower than SATA ext hdds? I know this to be true because I transfer data often and my USB 2.0 ext hdds will take about 2 minutes to move a 750Mb file while a SATA hdd will take about 45 seconds to move a 750Mb file.

    Thanks for the explanations. I like to learn. Please keep them coming.
  10. aidan80

    aidan80 Private First Class

    Exactly, SATAII will allow up to 300MB per second and USB 2.0 up to 480MB per second in theory. Keep in mind there are a lot of variables that can either bog down or increase performance. e.g. disk fragmentation, other data moving along the bus, CPU type and speed, memory amount, type and speed.

    The reason the USB drive is moving data slower maybe down to a number of factors.

    • Drivers immediately spring to mind, keep them up to date and follow the manufactures instructions for installing the device.
    • Motherboard compatibility also springs to mind check the BIOS and check for updates relating to the SATA and/or USB bus
    • Windows (assuming your running windows) updates can also be critical
    • Slow/busy processor may slow things down
    • Memory/RAM type and speed will have a big impact
    • Disk fragmentation on the source and destination disks
    These are just some suggestions that might be causing the slow down. Best thing to do is make a list of possible causes to the symptoms then go through the list one at a time ruling each out till you either run of things to try (there will be more to try lol) or till you find the cause.

    Give us a bit more information on your machine that may help and if you've used any or both devices on different machines. The more information we have the easier it'll be to figure out what’s wrong.
  11. aidan80

    aidan80 Private First Class

    I forgot to mention two different disks may also have different sized buffers which will have an impact on transfer rate they may also have different RPM speeds which again can have an impact as can seek/read or access times.

    Don't forget just because the hard drive has a USB connection if it's external it may well be an IDE drive bridged onto a USB controller then connected via USB. Standard IDE or EIDE (also known now as PATA formerly ATA or UDMA mode 5) interface speeds are rated at burst speeds of 100mb and 133mb e.g. IDE 133/ATA133 or IDE 100/ATA100. There are older versions of this ATA 33 and ATA 66.

    Burst speed is the speed at which the processor can pickup information from the cache (there's that cache again) on the hard disk controller and pull it in. When the cache runs empty it need to take it directly off the disk. With IDE this is where things take a nose dive and speeds go from 100mb - 133mb per second right down to 30mb - 50mb per second or there abouts. The larger the cache the more it can hold and in theory as long as the cache has what the processor wants then the longer you can run at "top speed".

    Also the processor has it's own "cache" which can store information for very brief periods of time and can help in those transfers. e.g. copying files on an Celeron 3.0Ghz and on a PentiumD 3.0Ghz may be very different and it can very easily come down to the buffers or cache memory that is assuming they are both running at the same bus frequency as well as internal frequency.

    I know this all gets very big and confusing very quickly... All you want to do is transfer some files but there really is a "lot" of other factors.
  12. Denise_M

    Denise_M MajorGeek

    - All of my drivers are up-to-date (know for a fact)
    - The ext hdds are connected to USB 2.0 HUBs. I have 4 of them. Two are connected to a USB 2.0 port on my pc and the other 2 are daisy-chained from each
    - My BIOS is up-to-date. ASUS hasn't updated it in a few years.
    - I don't know what a SATA and a USB bus is
    - I'm having problems with a certain update. SP2 installed a wups file and it's associated in the registry. One of the updates removes the association in the registry but leaves the wups file, which causes havoc, and I mean real havoc. I did 2 Repairs and a format. Since the format, I've been downloading and installing one update a day until I find the one that's causing the problem, but I used to have Automatic Updates turned on. To tell the truth though, it seems that my computer runs slower since a number of updates have been installed.
    - I have a pretty good processor . . . AMD Athlon Gforce 8400 64 X2 4200+. Whenever I look in Task Manager, Process Idle Tasks is between 97 to 99.
    - My RAM is pretty good too . . . Ballistix 2x1G RAM, 184-pin DIMM, 128MX64 DDR PC3200, Unbuffered. This was the middle speed. I should have purchased the fastest speed, though.
    - My drives are defragmented often. I use Disk Defragmenter GUI and then Windows Defragmenter. I also use Advanced Windows care. It's like CCleaner for a 64-bit os. It keeps my pc pretty clean and I run it once a day. I also run AdAware once a day and MBAM and SuperAntiSpyware once or twice a week and Avast! in full, in-depth mode about once a month. I don't have any trojans or viruses. The scans usually just show some cookies and AdAware will find an MUI object or two.
    -I only buy ext hdds that have 7200rpm, 16mb buffer. My internal hdd is a Seagate Barracuda 7200.10 SATA 3.0 Gb/s 320Gb.

    I built this computer with the help of a bunch of great people here. It was one heck of a thread . . . I think it had over 800 posts. http://forums.majorgeeks.com/showthread.php?t=116772
    I learned a lot about computers hardware at the time and I've learned a lot more since then, and about software/firmware/driver updates since then.
  13. rmyere

    rmyere Private E-2

    OK WHOA WHOA WHOA!!! Slow down here!!! There has been quite a bit of a mixup of data speeds concerning SATA and USB here. Let me explain. First in the short run-

    A SATA (one or two) drive in a USB 2.0 external enclosure WILL ALWAYS run at USB 2.0 speeds, as it is slower.

    Now for a bit more detail-

    1. SATA l runs as 1.5 Gbit/s. This is the same as 150 MBytes/s

    2. SATA ll runs at 3.0 Gbit/s or 300 MBytes/s

    3. USB 2.0 runs at 480 Mbit/s or only 60 MBytes/s

    Now keep in mind, these are ALL theoretical numbers, especially the USB ones. In real life, USB runs at a bit less than half of its rated speed. You must understand the difference between 1 Mb and one MB. The first is a MegaBIT and the second is a MegaBYTE. A MegaBYTE is much larger than a MegaBIT. In Fact, it is eight times larger. So USB 2.0 is way, way slower than either version of SATA.

    Anyway, the maximum speed of SATA has not even been achieved, as HDDs cannot even go as fast as SATA l. They transfer Data at about 80-100 MBytes/s. This is a very rough estimate as there are many different types of hard drives. I would recommend getting a hard drive enclosure with a firewire, or even eSATA port to connect to your computer if you are looking for speed of data transfer. Otherwise, your limiting factor will most assuredly be the REAL USB 2.0 speed of about 20-30 MB/s.
  14. Denise_M

    Denise_M MajorGeek

    So there's no way that a SATA drive in a USB enclosure can run as fast as a SATA drive connected using a SATA cable?
  15. rmyere

    rmyere Private E-2

    Absolutely no Way. Best Case, about one-third the speed
  16. aidan80

    aidan80 Private First Class

    Excellent advice.. I can't believe I forgot about the real speed!.. That's what I get for staying up too late!
  17. Denise_M

    Denise_M MajorGeek

    Thanks, rmyere, for clearning that up. Whenever one of my externals fails, I buy a SATA to replace it. I have a lot of drives so I'm looking into buying multi-enclosures and I found a few SATAs to choose from. They're expensive but they'll be worth it.

    I copied and pasted the info you gave into a Word Doc so I can refer to it.
  18. dsalsa

    dsalsa Private E-2

    Great info about SATA and USB.
    Can you give me information about using a SATA drive in an external enclosure and connected to your computer via a PCMCIA 2 Port Serial ATA (SATA). This is the description about the PCMCIA card: "Up to 1.5 Gb/s data transfer rate for SATA 32-bit 33 Mhz Host interface compliant to PC Card Standard Compliant with Serial ATA 1.0 specifications Supports two independent Serial ATA (SATA) channels"
    The drive I'm thinking of using is a: SERIAL ATA/300 INTERFACE, 7200RPM, 8MB Buffer.
    One more thing I would have to use a power adapter serial ATA (Connect your high speed Serial ATA drive to your power chain with our 4 Pin Molex to 15 Pin Serial power adapter. This power connector can be used with both 3.5 " and 2.5 " Serial ATA devices).
    Is this just a crazy idea or what?
  19. Denise_M

    Denise_M MajorGeek

    I'm not sure if this will answer your question. If it doesn't and no one else responds, it would be best to start your own topic because adding to someone else's topic is not looked on favorably because it confuses the original topic.

    I purchased a NORCO-4618 PCI-X / PCI eSATA / SATA II / SATA I Controller Card that has 4 external SATA ports. I had to install the Silicon Image SiI3124 driver for it. http://www.newegg.com/Product/Product.aspx?Item=N82E16816133002

    I also purchased a 5-port SATA hub http://www.cooldrives.com/sahub5muussi.html

    I connected the cable into one of the ports on the Norco controller card.

    All my SATA drives worked with no problems when they were connected to the SATA controller card and the SATA hub.

    Hope this helps.
  20. jlphlp

    jlphlp Master Sergeant

    Hi All,

    I don't believe that anyone has mentioned the most important thing here. All Hard Drives are basically SERIAL devices. Data is read and written serially. With IDE drives the serial data must be converted to Parallel. With SATA Drives no conversion is needed.

  21. collinsl

    collinsl MajorGeek

    The idea is perfectly logical and sound and it would work perfectly. However, the drive would only operate at SATA1 speeds, which is 1.5Gb/s

    Are you sure you would need a power adapter inside an external enclosure? If the enclosure supports SATA drives it should be fitted with a SATA power connector as standard, as the external caddy will not draw power from the computer.
  22. theefool

    theefool Geekified

    Where do you get this information?
  23. dsalsa

    dsalsa Private E-2

    Thanks for your reply's. I understand that the drive would only operate at SATA 1 speeds and that is because the PCMCIA card only works up to 1.5Gb/s.

    Unfortunately I would need the power adapter inside my external enclosure because the enclosure I have is not for a SATA drive it's for a PATA drive in fact I hope the PCMCIA card comes with a data cable or I will have to buy that too. My enclosure is not only for a PATA drive but it's for USB 2.0 Maybe I'm better off just buying a new enclosure that suppors SATA drives.
  24. collinsl

    collinsl MajorGeek

    I do not see how you could get a USB 2.0 PATA caddy to operate with a SATA link and a SATA hard drive. You would be better off buying a suitable caddy.

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