I upgraded my hard drive from HDD to SSD.

There is no change in download speed. Reviewer says SSD has very good write speed, but why does that not increase download speed?

closed as off-topic by Max Ried, Monomeeth, Tetsujin, fsb, klanomath Mar 28 '17 at 19:45

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    I wanted water to flow out of my hose faster, so I bought a thicker hose. The flow rate stayed the same. Why's that? Because the water supply to my house is the limiting factory (the bottle neck), not the thickness of my hose. – Alexander Mar 27 '17 at 19:04
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    @Alexander because hose thickness has no equivalent here. It's more like asking: "I made my crop irrigation channels more efficient, why isn't water coming out of my hose any faster?", or "I just switched to a high-flow toilet, why aren't I peeing any more quickly?" – Slater Victoroff Mar 27 '17 at 21:16
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    @SlaterTyranus There's no rule that says you can't pee faster than your toilet can drain. It'd be gross, but it's possible, which is why your example doesn't work. But I digress. – Alexander Mar 27 '17 at 21:43
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    I bought a sports car, but traffic is still slow on my commute home. – chrylis -on strike- Mar 27 '17 at 21:48
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    @Alexander, not to beat a dead horse, but there's no rule saying you can't download faster than you write to disk if you just throw out the extra packets. Like the toilet, it's gross, but it's possible. – Slater Victoroff Mar 27 '17 at 22:06

Your internet speed is a lot slower than the hard drive speed, so upgrading to a faster hard drive won't significantly increase download speed. It is your internet connection that's limiting your download speeds, not your harddrive.

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  • I disagree with the word 'significantly', but I like the smileys. +1 – RaisingAgent Mar 28 '17 at 8:31
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    Thanks lol, I prefer visual explanations with smiley faces, its good to see I am not the only one. :) – kiwicomb123 Mar 28 '17 at 8:36
  • While I completely agree with everything here (including the smileys), I don't like paradoxical questions/answers in general. If he were to have internet bandwidth that surpassed his SATA bandwidth, he would be in a data center; which would mean he would already know the answer to this question which would then mean the question would never get asked..... +1 for the diagrams and the good karma. – Allan Mar 28 '17 at 16:32
  • +1 for the picture. Could you add in a third case, where the internet connection's a T1 line, the harddrive is actually a top-tier RAM disk, and the remaining RAM is virtual RAM stored by a low-end flash drive? And then a fourth case, where everything's top-tier components, but the computer itself is moving near the speed of light relative to the smiley face, such that time dilation's significant. – Nat Mar 28 '17 at 19:23

Probably the bottleneck is not your disk but your network.

A SATA2 hdd disk usually supports write speeds of up to 250/300MB/s. It is unlikely that you can reach those download speeds.

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    It is probably worth noting that 300 MB/s would be the same thing as an internet connection marketed as 2400 mbit/s. – trognanders Mar 27 '17 at 18:41
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    that is to say, there's a factor of 8 difference between bits (abbreviated with a lower-case b) and bytes (abbrv. upper-case B). Network speeds are almost always quoted in bits per second. – Nick T Mar 27 '17 at 18:45
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    Actually probably more, because of TCP/IP overhead and the like... so you'd need an "advertised" download speed closer to 2600-2800 mbps (or 2.6-2.8 gbps). Not to mention, even modern computers only have one-gigabit network cards so if you had such a connection you'd still be bottlenecked by the network and thus would never see more than ~120MB/s downloads. – Doktor J Mar 27 '17 at 21:09
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    Actually, HDDs have (usually) a maximum speed of 150-200MB/s. A gigabit connection has a theoretical maximum of 125MB/s. I've never seen a maximum of 110-115MB/s of upload/download between 2 computers. I would say that the bottleneck is everything past O.P.'s network card. – Ismael Miguel Mar 28 '17 at 11:02
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    @DoktorJ Not only IP and TCP have an overhead, SATA also have a overhead. (but less than TCP and IP) – 12431234123412341234123 Mar 28 '17 at 12:27

Upgrading your HD will not help with download speed. A better internet connection will help you have more download speed.

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    This is not true. In the unlikely case where your drive is slower than your download speed, upgrading the drive will make your downloads faster. – isanae Mar 27 '17 at 21:23
  • @isanae In particular, if you use a could-backed drive, increasing the speed of the drive will definitely make your downloads faster. – DepressedDaniel Mar 27 '17 at 21:50
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    A local download could easily be throttled by disk speed - I back up to and restore from a hard drive on my network. The cabling can support 1Gbps; the hard drive which I restore to (my internal computer hard drive) is just 65MBps and is the big throttle when restoring any data. – Tim Mar 27 '17 at 22:29
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    Also, if other processes are competing for disk I/O at the same time, then an SSD would be much better at handling all of the requests simultaneously (because no seek time). – Dan Henderson Mar 27 '17 at 22:35

Reviewer says SSD has very good write speed, but why does that not increase download speed?

One has absolutely nothing to do with the other.

To use a car analogy, you are asking why, given that you upgraded from a Toyota to a Porsche can you not load groceries into your trunk any faster.

Your download speed is governed by three things:

  • The speed(s) offered by your carrier
  • The speed your router/modem is capable of
  • The bandwidth the devices on your network is capable of (i.e. your gigabit NIC card)

If you didn't address any/all of these points, your download speed would have no change whatsoever.

As for the bottlenecks addressed in the other answers, let me assure you that the data transfer rate of a SATA III interface is 6Gb/sec while your NIC (network interface card) at most will be 1Gb/sec. Your internet, unless you live anywhere in Korea or lucky enough to live where there is Google or Comcast Fibre, it's probably around 100Mb/sec. This mean your drive is about 600x faster than your network - the bottleneck argument is a moot point.

  • Careers don't offer speed: they only offer you a certain slice of maximum bandwidth that you can use at any given time. If you have a connection speed of 130Mb/s (like me), that means that you can send and receive up to 130Mb a second. This includes uploads and downloads. – Ismael Miguel Mar 28 '17 at 11:07
  • @IsmaelMiguel Did you mean "carriers"? I think the difference between an offered speed and offered maximum bandwidth is academic at best. Yes, technically it's maximum bandwidth, but when was the last time you heard a Comcast/AT&T/other mega ISP commercial that said "we have the largest maximum bandwidth allocations of any ISP!" -- no, they say they offer the fastest speeds. Technically not correct, but the semantics are beyond your average user (or marketer). – Doktor J Mar 28 '17 at 15:54

I was not really pleased by either answer here, so here we are.

When speaking in terms of a download speed, changing your disk drive will never have an effect on that. There are 4^2 possible bottlenecks when downloading a file(s) from a server across the internet.

1) NIC (Network Interface Card)

2) Physical Ethernet cable or WiFi connection to the router

3) LAN connection speed

4) WAN connection speed

And then the same in reverse on the server side.

As some comments have mentioned, it does not matter if you have a HDD connected via IDE at speeds of 5 MB/s, or a SSD that could write at crazy speeds of 10GB/s. The network will always be the bottleneck.

On the higher end of ISP packages, you can get 100Mb/s. That is Megabits, not Megabytes. Meaning the fastest your download speed ever will be, in perfect circumstances, is 10MB/s (Megabytes). Note: there are some fiber ISPs now offering Gigabit connections, but those are extremely pricey and usually used by very bandwidth needy businesses.

Take this scenario below, which would be an average user setup:

-Laptop(newer with 802.11c) connected via WiFi to a router. = 300 Mb/s

-Cable internet connection = 25 Mb/s

-SSD = 300 MB/s

-Download a file from Google Drive = 2.5 Mb/s

As you can see, the bottle neck there is your ISP connection. Here is another with an older laptop with a WiFi bottleneck:

-Laptop(older with 802.11g) -> WiFi to router = 54Mb/s

-High Internet connection tier = 100Mb/s

-Download from Dropbox = 5.4 Mb/s


Almost always, your bottleneck will be because of one or more of these 3 things: WiFi, ISP connection, or a slow server/ISP on the other end. Never your disk drive.

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