Bittorrent Sync Slow Lan Speed

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Hi Y'all


I have used BitTorrent Sync for almost a year now, and it has worked great. I have synced hundreds of gigabytes data between Windows-Linux and Linux-Linux. The speed has been extremely high, with an upload to 60 MB/S (Default settings, encrypted data etc.). However, when i recently changed to a Windows server, everything slowed down. Now I get speeds from 100 KB/s to 2 MB/s, a big difference if you have to upload 1 TB of data.


My setup:


Both windows Pc (8,1 and Server 2008 R2)


BitTorrent Sync 1.3.109 with predefined hosts, disabled relay server and LAN for forced predefined, disk priority is set to high, no encryption, no limit on local peers, buffert size maxed to 99999 and everything manually port forwarded in Windows firewall


Connected with Cat6 cables, gigabit router and computers. I tried with the latest release of Sync, the speed spiked for a minute at 120 MB/s, then dropped to the regular speed.


What am I doing wrong? Appreciate ALL Help! 

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  • 2 weeks later...


To get some solution I need to find out the root cause. It may be different for different environments - most users bottleneck is the hard drive. So I suggest trying to set "hdd_low_priority" advanced preference to "false" first of all and increasing send / recv buffers size (also in advanced preferences).

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I'm experiencing the same issue.  Systems on both sides are running Server 2012.  System 1 has an 8 drive SATA 6Gb ZFS array, System 2 has a 12 drive SATA 3Gb ZFS array.  I've benched system 1 at 1.6GB/s write speeds and I'm only getting peaks of 20MB/s sync speeds.  System 2 isn't as fast but it is purely a storage server with nothing else writing to it.  Both systems have 4x 1GbE Load Balanced connections using Intel Pro/1000 NIC's.  As you suggested, I'm collecting the speed profile and will email it shortly.  I set hdd_low_priority to false as suggested which improved peaks slightly but it still is constantly dropping down to nothing.  Increased send/recv buffer size to 1000 on both sides, that didn't seem to have any effect.  

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  • 5 months later...

Similar problem, although I've just made the move from Dropbox to Sync. It's extremely slow at about 500kbs - 1Mbs over LAN, and even slower over the internet. Dropbox was much faster at syncing, so I'm not sure where the bottleneck would be. I've sent my speed profiles to . Hope to hear back from you guys soon. 

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