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I've been running the bitcoin-qt client for over a week now trying to catch up with the block chain (closer to three weeks if I count the first time I had to synchronize everything). Looking at my bandwidth usage, I'm only getting 2-5 kB/s at any given time.

I did a ton of Googling and noticed a lot of others were complaining about the long synchronization process, but none of them seemed to be as long as mine (and no one made mention of their speeds). Is it supposed to be this slow, or have I set something up incorrectly?

I should further clarify that this is not a new issue, this has been persistent since I started using bitcoin over a year ago.


Further information:

The client is always at or below 8 connections to the Bitcoin network (if that is at all relevant/useful information). I have UPnP enabled.

Computer: I'm using a laptop (OS: Win7 64-bit) from a few years back, so inherently the specs aren't tops (but by no means terrible) - the CPU is an AMD Athlon II M300 (2 cores / 2 threads, 2.0 GHz, 1MB cache).

CPU Usage: According to perfmon, bitcoin-qt averages 7% CPU consumption.

Blocks processed: 124 in an hour (I also made a list breaking it up into 10-minute increments and it averaged 1.8-2.0 blocks per minute of those increments, so it agrees with the hourly rate without much fluctuation).

  • I recently also have downloaded the complete block chain. It took me a few hours (close to 8 to 10 i believe). But the complete BitCoin folder currently holds more than 8Gb. So maybe 1 Gb an hour... – Rik Verbeek May 2 '13 at 10:30
  • My wallet seems to increase faster than it decreases! I started logging blocks remaining. It has been on for 4 days now. Core 2 Duo 4GB Ram WinXP. CPU is at 0-5% and I have a 20mbps Internet pipe. WTF. 40761 35834 39716 37544 38214 38376 40918 31264 40728 40896 40922 – user4891 May 8 '13 at 4:36
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The synchronization process may be slow on slow computers - it does not only rely on bandwidth. After downloading a chunk of blocks from various peers, the Client needs to verify every transaction in them, which is a very CPU intensive task. If you have a slow computer, this will be the bottleneck - you will spend a lot of time verifying the block and only a little downloading them, making the average download speed small.

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If you have not set up port forwarding correctly you will only be able to connect to 8 others. If those 8 others do not have a generous connection to you it could be very slow. (This is worth checking)

Aside from that your CPU should be hard at work compressing old blocks and verifying all blocks.

Aside from that your disk will have a lot of random access (also because of the compressing and verifying) and might be the bottleneck.

You might scour the Internet for a recent version of a downloaded blockchain, or resort to using a light client or webwallet.

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What kind of computer are you using? It's not just downloading the blockchain, it is also verifying it and creating the databases locally. This can be fairly CPU intensive. 2-5KB seems very slow, but maybe you just caught it at a slow point.

  • Check your CPU using Activity Monitor/Perf Mon. If you are seeing high CPU, that's a good thing. You might just be downloading as fast as your CPU can process blocks.

  • Hover over the spinning icon in the bottom right. It will tell you the exact number of blocks processed. Write down the current block it has completed, come back in an hour and see how many you've progressed.

If you have a particularly slow/old computer, this might be normal. If you don't seem to be CPU limited, or you aren't making decent progress when you are looking at the actual block counts, then post a follow up to your question with some more specifics. (Such as what computer you are using, what you are seeing in terms of CPU usage, and how many blocks you have processed over what period of time.)

Update based on comments:

I'm starting to think that Lodewijk and his answer has the right idea here. I had originally thought that 8 connections probably wasn't the issue because even eight connections should be more than a few KB per second. But if they are poor connections they might be your issue. Did you open the open the Bitcoin port in your firewall and port forward it to you laptop?

  • Computer: I'm using a laptop (OS: Win7 64-bit) from a few years back, so inherently the specs aren't tops (but by no means terrible) - the CPU is an AMD Athlon II M300 (2 cores / 2 threads, 2.0 GHz, 1MB cache). CPU Usage: According to perfmon, bitcoin-qt averages 7% CPU consumption. Blocks processed: 124 in an hour (I also made a list breaking it up into 10-minute increments and it averaged 1.8-2.0 blocks per minute of those increments, so it agrees with the hourly rate without much fluctuation). – zants May 3 '13 at 3:30
  • I just saw your update. I attempted to open the port but I'm unsure if I did it correctly (I noticed no difference after doing this): i.imgur.com/YesfB1q.png. / The ports have always been open in my firewall, but I've always wondered why there were so many duplicates (not sure if that's an issue): i.imgur.com/ePojzmz.png – zants May 10 '13 at 7:04

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