I am experiencing very slow ethernet date transfer speeds using backup Time Machine with a new Time Capsule 3TB and EL Capitan v10.11 Beta (15A225f) on an iMac 24in 2009. Ethernet cat5e connected directly. The speeds are about 5GB in 12 hours and wifi transfer speed (of course) is even slower. Never tried it with Yosemite on iMac as El Capitan installed prior to Time Capsule purchase. However tried backup Time Machine on MacBook Air 13in 2013 that has Yosemite and found normal fast ethernet transfer speed (USB ethernet adapter used) to the same Time Capsule. Also, SAFEBOOT of El Capitan on iMac revealed very slow data transfer speed of backup data of Time Machine to Time Capsule. However, data transfer of files NOT Time Machine to a USB Seagate disks attached to USB on back of Time Capsule revealed rapid data transfer. I have not yet tried Time Machine backup to USB Seagate drive attached to back of Time Capsule. I have erased the Time Capsule disk with each attempt (no other data or partition on drive).
El Capitan slow ethernet data transfer using Time Machine backup to Time Capsule
I also have a very slow Time Machine data transfer speed (less than 1 Mb/s over a gigabit Ethernet interface) while trying to backup on a file server (Mac mini under 10.10.4, server version 4.1.56 (build 15S2186i). The backup size is ca 30 GB, it hangs up before the end :-(
I have the same issue and after tyring to backup it never backups anything. This started after I installed the Public Beta 3 of El Capitan. Let me know if you guys are actually getting the backup to complete even with the slow connection?
I'm having the same issue, bot only since beta 4 installed (currently beta 5). trying to look through logs etc to see what is going on.
FYI, currently stalling at about 2.8MB out of 60+ Gig backup, no successful backup in the last 10 days (since before beta 4 was installed), this over ethernet to a Mac Mini running Yosemite 10.10.4 and Server 4.1, from EL Capitan v10.11 Beta (15A235d).
The following thread has some suggestions by Max108, I'm trying a couple of them now.