How does the performance of an external SSD drive compare to an internal?

I'm assuming the connection would be USB 2.0 - would that be the limiting factor in speed? Is it a waste of money?

EDIT - To Clarify; what I really want to do is to decrease build time in Visual Studio. I've been told that SSD is the answer to all my problems; but it's a work machine and I'm not sure of the internals and I'd prefer not to have to crack it open.

I currently have a ST3250310AS Barracuda drive.

Also - how do flash drives compare to SSD?

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    using eSATA as connection would be equal to internal, unsure about USB2 but it will surely not be optimal – Joakim Elofsson Feb 17 '10 at 17:02
  • As to flash drives, here's a link: superuser.com/questions/104524/… – Xavierjazz Feb 17 '10 at 17:14
  • "what I really want to do is to decrease build time in Visual Studio." then anything USB 2.0 will only add to your woes. :) – Molly7244 Feb 17 '10 at 17:16

We have easily updated some Lenovo Thinkpad T61P and Dell Precision M4400 at work with an internal SSD. In both case you just need a screwdriver and in 5 minutes you can substitute your HDD.

I can say that the performance are stunning compared to the previous disk. The boot is really fast and also the launch time Visual Studio 2008, SQL Management Tools and office applications like Lotus Notes, Word, Excel is reduced.

I did some benchmark on build times, but we don't have a big project with thousand files, only many small projects with hundred of files. In any case I measured a performance increase by 25%.

I did some benchmark on some queries on a local database and in this case I found an increase of 50%.

Pay attention that with XP the performance with SSD decreased in time, you need to wipe the cell with a program from the manufacturer, time to time.

Buying an SSD for external USB 2.0 drive is a waste of money. With USB 3.0 things are going to be interesting.

  • "Buying an SSD for external USB 2.0 drive is a waste of money" - do you have any data to back this up? – Nicholaz Feb 17 '10 at 17:26
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    USB 2.0 has a limit of 60MB/s. Current SSD drives can maintain up to ~250MB/s. Also, USB was not designed for high performance, but for simplicity and low cost. References to Wikipedia's article on USB might be a good starting point to look for information. – liori Feb 17 '10 at 18:20
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    USB 2.0 has a theoretical limit of 60MB/sec, but in the real world you're lucky to get much more than 30MB/sec. In my experience with a number of external USB 2.0 drives, you don't often see much more than 20MB/sec. tomshardware.com/reviews/usb-firewire-esata,2534-5.html – John Rose Feb 18 '10 at 15:08

Yes and no.

SSD over USB 2.0 is a waste. With SSDs capable of pushing up to 200MB/sec and beyond, why limit them to USB which can't push more than 30MB/sec in the real world? http://www.tomshardware.com/reviews/usb-firewire-esata,2534-5.html

If you're going to spend the money on a SSD, get it installed internally. Then drop your old internal drive into an inexpensive enclosure and use it for backup or aux storage.

However, it must also be said that much of the "real world" benefit of SSDs comes from their decreased latency and excellent performance on small, random file accesses -- which is what your OS and applications are doing most of the time. And that kind of file access will not be bumping against the 30MB/sec limits of USB 2.0.

Sequential throughput speeds (those gaudy 200MB/sec numbers) are only seen when you're reading or writing large files.

Here's what Joel Sposky wrote about SSD's impact on his team's software build performance. http://www.joelonsoftware.com/items/2009/03/27.html In a nutshell, it didn't speed up their build times. However it does make everything launch more quickly and feel more responsive and from personal experience I can tell you this will make you a bit more productive (or at least less frustrated :P)


USB 2.0 claims to support data transfer rates up to 480Mbps, and SATA II (Let's say you want to compare with Internal SATA II) claims to support data transfer up to 3.0Gbps (using 10/8 bitstuffing – actual “throughput” is lower). Sata III is 6.0Gbps....

If it's an external HDD for backup or storage, USB 2.0 is way ok.

  • The question was whether an external SSD over USB 2.0 would be usefully faster for programming builds than a HDD. I don't see how "an external HDD for backup or storage" is relevant, nor how reeling off stats about different protocols helps when the question is about the merits of different types of drive on the same protocol. – underscore_d Jul 9 '16 at 12:52

On an internal SSD (Intel X25M) I have decrease of build time by almost 50% (22sec vs. 40sec) on an i5 machine (VS2005). The throughput of the SSD is about 190MB/s per sequential read, nonsequential is slower, which does not even nearly take the full bandwidth of the SATA bus.

I have no hard data to back this up, but I believe that with raw (CPU) compile time the disk throughput will not hit the limit that USB will impose. Especially if the VS installation remains on the internal disk so that the read of the VS program/build tools and project is decoupled.

Just because USB2.0 is slower than SATA does not necessarily mean that using an SSD through USB2.0 is a waste of money.


Have a look at this, it shows the difference between E-Sata and USB. I know its not exactly what you're asking but does demonstrate the differnce in speeds between Sata and USB connections. (I know the connection is E-Sata but for comparisons sake)


An external drive using USB is always going to be a slower transfer speed than an internal Sata connected drive.

EDIT: To Use E-sata you would more than likely have to install an E-sata Card such as this: http://www.amazon.co.uk/gp/product/B001FB6WK0/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=103612307&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B000X432D0&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=04T3YRAMKMZNVYRFQYVJ

I didn't realise it was a work machine sorry. If you're looking at improving speeds from an internal HDD then an external USB2 SSD drive is not the way to go.

  • When slower than the internal SATA, the question is, is it still faster than the SSD – Nicholaz Feb 17 '10 at 17:15
  • I'm sorry I don't quite understand what you're asking. Is the USB 2 connection faster than the SSD drive? If so - No – Joe Taylor Feb 17 '10 at 17:17

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