Why is my Bitcoin Core downloading progressing so slowly at the end?

[markcolls]

For reference I'm downloading it over Tor.

The first 80% downloaded at a fairly good rate of 5%-7% per hour, but then it got blisteringly slow - between 0.1% and 1% per hour. Why is it all of a sudden downloading so slowly at the end? I have tried restarting tor and generating new circuits, but its still really slow.

So my two questions are why has it gotten this slow at the end and is there anything I can do to speed it up?

[nc50lc]

Is "first 80%" an approximate? Anyways, there are some reasons:

• Older blocks have less transactions in them, making the download size of each blocks low making it sync faster.
• Some blocks from genesis block to block height 453354 (refer to the edit) are being assumed as valid and won't require verifications that could speed-up the sync process.
• Etc.

.
Note: I checked the code and the latest indicates that the default is now: Block Height 654683 (link).
I don't know when (version) it was changed.
-Edit-
Found it, that was 28days ago (Pull Request link) and it was 623950 before that.

So my two questions are why has it gotten this slow at the end and is there anything I can do to speed it up?

If you haven't touched the dbcache (database cache), you can increase it based from your available RAM (about half+).

[markcolls]

Is "first 80%" an approximate? Anyways, there are some reasons:

• Older blocks have less transactions in them, making the download size of each blocks low making it sync faster.
• Some blocks from genesis block to block height 453354 (2017) are being assumed as valid and won't require verifications that could speed-up the sync process.
• Etc.

.
Note: I checked the code and the latest indicates that the default is now: Block Height 654683 (link).
I don't know when (version) it was changed.

So my two questions are why has it gotten this slow at the end and is there anything I can do to speed it up?

If you haven't touched the dbcache (database cache), you can increase it based from your available RAM (about half+).

So where it says "Progress XX.XX%" in BitcoinCore it is reporting by percentage of blocks done and not percentage of GB done?

[ranochigo]

So my two questions are why has it gotten this slow at the end and is there anything I can do to speed it up?

Other than the other two, you can actually improve the speed by making Core assume that blocks are valid up to a certain higher block height. I do not condone this as it means that you're validating your block less and that if whatever data source you're getting the block height from is malicious, you'll have very serious repercussions.

Else, whatever nc50lc said is correct. If you're synchronizing a Bitcoin Core instance for your own usage, you can only increase dbcache to improve the synchronization. In my case, I was synchronizing the testnet client so it wasn't of much risk for me to do so.

[nc50lc]

-snip-

So where it says "Progress XX.XX%" in BitcoinCore it is reporting by percentage of blocks done and not percentage of GB done?

Yup, it's based from the number of downloaded/verified blocks and the tip, not the size.

[cbno79]

I am having similar trouble downloading the Bitcoin core.
Its stuck at 89%.
Where and how will I edit the dbcache please

[LoyceV]

Where and how will I edit the dbcache please

Settings > Options > Size of database cache > xxxx MB
But it depends on how much RAM your system has (available). If your system has 16 GB, you can try 8192 MB. If your system has only 4 GB, it's time for an upgrade