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Solve : Question - Scan a HDD as an external drive?? |
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Answer» Hi, Quote from above website.I personally have a USB 2.0 WD external 500GB HDD which takes around twice to thrice as long to complete file transfers when compared to my internal HDD, so.. I wouldn't be surprised at the statistics above. Note that the above statistics use external SATA. Here are a few professional links concerning SATA vs USB vs eSATA: http://www.wfu.edu/~yipcw/atg/disk/usb3/ http://blogs.gurulabs.com/dax/2009/07/esata-vs-sata-v.html http://www.rt.db.erau.edu/655s08/655webUSBSAT/index.htmYou might also try ClamWin Portable, which runs from a flash drive. If you GET it, update its virus definitions before running a virus scan. Ok, I will try it. So, If I run a scan of a HDD (That has an OS of another machine) as an external HDD on another machine, it's good ?Quote from: nasroo7 on December 24, 2011, 01:27:55 PM So, If I run a scan of a HDD (That has an OS of another machine) as an external HDD on another machine, it's good ?Well, running a scan in such a way may be necessary if the OS on the external HDD has already been seriously compromised by a virus to the extent where it is unusable.Quote from: Transfusion on December 23, 2011, 08:47:03 PM There is a difference between the transfer speed of direct SATA connection to the motherboard and connection via USB enclosure. Not really. Very few magnetic platter drives come very close to saturating ATA-6, which has a max speed of 133mbps. For SATA, while there is a higher maximum throughput, I doubt even a really fast SSD could fully saturate the 480mbps USB. The fact is, though, that the test you quote is somewhat stupidand not really a test. All it proves is that two drives from different manufacturers are likely to have different properties. A better test would be to use the same drive INTERNALLY and EXTERNALLY, rather than testing the speed difference between an external drive (which typically are built using 5200RPM drives) compared to a internal drive. Basically, the test isn't testing the bus speed the devices are connected to at all, merely the speeds of the devices. Quote I personally have a USB 2.0 WD external 500GB HDD which takes around twice to thrice as long to complete file transfers when compared to my internal HDDThat's because of the drives, not the bus (USB/SATA) being used. I have several IDE enclosures and I used to have a SATA enclosure and there was no marked difference in transfer speeds between when I used a drive in the enclosure or had them inside a computer (with the exception of when connected to a machine that only had USB 1.1, of course). A slow drive was slow regardless of whether it was plugged into the enclosure or not. And faster drives didn't seem affected by being connected via USB. Quote Here are a few professional links concerning SATA vs USB vs eSATA: Of course the ACTUAL Bus speeds between SATA and USB differ. But as far as I'm aware there aren't any drives made yet that can come close to saturating the USB bandwidth. As to the topic, though- it's usually better to scan outside the OS, which includes using the drive as an external in another machine. Primarily because if the system is infected you can't trust it for anything, including scans.I love you, BC, you keep continuing to supplement my knowledge and fill in the myriad of gaps that I have. I sincerely wish you a Merry Christmas! I do WONDER why http://techreport.com/articles.x/18077 claims that "Every hard drive we've tested saturates [USB 2.0's quoted 480Mbps.]" Even if I had a 5200 RPM external drive which presumably would never be able to saturate USB 2.0 it shouldn't spend twice as much time completing file transfers as my internal 5400 RPM drive...You got me thinking about USB 3.0 drives. That means... manufacturers claim that the transfer speed will be faster due to the fact that the enclosure supports USB 3.0(which BTW has a quoted max speed of 5Gbps, or 600MB/s) but in fact all they have to do is slip a 7200RPM drive in, which will clearly be an improvement over a 5200RPM one? And then charge an extreme premium for the USB 3.0 port? EDIT: I just realized 480 Mbps is 60 MegaBytes/second. USB 2.0 is half-duplex. So... only 30 MB/s max in both directions? Any 7200 RPM drive will easily saturate that...Quote Even if I had a 5200 RPM external drive which presumably would never be able to saturate USB 2.0 it shouldn't spend twice as much time completing file transfers as my internal 5400 RPM drive...It will if the external drive sucks. Quote You got me thinking about USB 3.0 drives. That means... manufacturers claim that the transfer speed will be faster due to the fact that the enclosure supports USB 3.0(which BTW has a quoted max speed of 5Gbps, or 600MB/s) but in fact all they have to do is slip a 7200RPM drive in, which will clearly be an improvement over a 5200RPM one? And then charge an extreme premium for the USB 3.0 port?Not really. While it seems that some drives can in fact saturate USB2 (though I'm not clear what my test with an external enclosure and a EIDE drive shows), it's more likely they can stick with the same internal drive and get a speed boost anyway. I think the RPM speed of the drive influences access time more than speed, also. Quote EDIT: I just realized 480 Mbps is 60 MegaBytes/second. USB 2.0 is half-duplex. So... only 30 MB/s max in both directions? Any 7200 RPM drive will easily saturate that...USB has a number of modes, which includes changing the upstream/downstream bandwidth. However even in that light there are a number of drives that come close to and even exceed USB's quoted maximum as a result of that. I've never actually seen these drives, though, and my only sources are the same types of sites that I tend to avoid (such as the one you linked). here are the results of some of the tests I did myself just now. using my C: (internal) drive versus one of my external drives. My internal drive had a average transfer rate of around 80MB (Megabytes) a second. This would definitely saturate USB2, so I was wrong about that. testing a external USB enclosed drive, it seemed to max out at around 30MB/s. Though it's hard to say what that means, since like the quoted test, my "test" is tainted since my external drive is a different brand, model, and even interface (my external is EIDE whereas the internal drive is SATA). Maxing out at 30 though seems to work with your theory, and it looks like Drives now do exceed USB2. Also, further research sort of clears of a confusion I had, the ATA-6 speed is in fact not 133 Megabits per second, but rather megabytes per second, so PATA is truly a 1-gigabit speed. That said, we have to wonder how it would apply in this sort of scenario. Obviously for tasks like transferring files and copying files it will be slower, but the fact is the OP is discussing performing a virus scan on the drive. This will almost always be slower when you run it on the system drive since there are any number of programs hooking drive accesses, such as anti-virus programs, which will slow down any and all disk access in that manner. Also, if the drive is infected you've got the issue that malware can be doing the same thing (much like virut, which will infect files as they are accessed) That's a good info here! Thank you a lot ! and Merry Christmas to all of you Quote Obviously for tasks like transferring files and copying files it will be slower, but the fact is the OP is discussing performing a virus scan on the drive. This will almost always be slower when you run it on the system drive since there are any number of programs hooking drive accesses, such as anti-virus programs, which will slow down any and all disk access in that manner. Also, if the drive is infected you've got the issue that malware can be doing the same thing (much like virut, which will infect files as they are accessed) Ok... So actually that answers my question on why it takes longer when the HDD is scanned internally, than when it's scanned externally. It makes sense to me now And it means also that it's better to scan an infected HDD externally? (More effective?) Quote My internal drive had a average transfer rate of around 80MB (Megabytes) a second. This would definitely saturate USB2, so I was wrong about that. testing a external USB enclosed drive, it seemed to max out at around 30MB/s. Though it's hard to say what that means, since like the quoted test, my "test" is tainted since my external drive is a different brand, model, and even interface (my external is EIDE whereas the internal drive is SATA). Maxing out at 30 though seems to work with your theory, and it looks like Drives now do exceed USB2. Quote There is a difference between the transfer speed of direct SATA connection to the motherboard and connection via USB enclosure. Actually, If I manage to transfer data from an internal HDD (diskAlpha) to a second internal HDD (DiskBeta), and then transfer the same data between the same disks, but from an internal HDD (DiskAlpha) to an EXternal HDD (diskBeta) The time difference would mean that the SPEED transfer data between SATA to SATA and between SATA to USB2.0 would be the reason? since the data was transferred between the two same HDDs, but with a different road? |
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