This was making me crazy for last few days. On Monday evening I found the Time Machine backup for my iMac running Mac OS Yosemite to a Time Capsule 3TB device was last done a week back. I was puzzled why it didn’t run fully every after. I initiated a backup manually, left the Air Condition in the room running overnight as weather in Chennai can be in 30 Degrees Celsius even in the nights in summer like now. In the morning when I checked it had done some 50GB out of total 700+GB it has to have done. So on Tuesday evening I erased the disk in Time Capsule, replaced the Ethernet cable from iMac to Time Capsule with a new CAT6 cable. On Wednesday morning it was the same. I Google’ed and read through many of the articles, almost all of them said shutdown any Antivirus software you may be running, if you are using a Wi-Fi connect Ethernet cable, none of them relevant to my setup. I tried everything I knew, using Disk Utility I verified all the local disks, verified the disk permissions, killed all running apps except finder & backup and so on. Reindex Spotlight, nothing seems to help. I called the vendor from whom I bought the Time Capsule and gave him the device for a checkup with Apple local support.
Meanwhile I took out from attic an old Time Capsule 2TB device, connected it to my iMac and startup the backup. This time it was worse. After two hours it had completed 1GB out of 700GB+ and it was still showing “Calculating Time”. I knew something was terribly wrong, it can’t be the local disks – I have a SSD that is less than 2 months old which is the primary boot device, a WD 1TB Firewire HDD that seems to copy/play Gigabytes of video files effortlessly. That’s when I came across this 2013 article by James Pond, going through the list, item #6 caught my attention which talked “Check and/or change your Computer, etc. names if needed, per item #C9“. In that page he advices you to keep the Computer Name, Time Capsule Name, Wireless Network (not relevant to me) to not more than 25 characters long, avoiding special characters and no punctuation. When I checked my iMac and TimeCapsule had names that were longer than that, had spaces in them. I changed them to smaller name, restarted the iMac, repeated the backup.
I noticed in the next 1 hour about 60GB was completed and it was showing “About 7 hours remaining”. Thank you James Pond.
Update 25th August 2015:
After few weeks, the Time Machine backups started to get very slow again, clocking just 100MB in one hour. I used Disk Utility to verify permissions & verify disk; then I changed the Full Name of the Administrator user in OS X from a long name with space like “Venkatarangan Thirumalai” to a simple name “Venkatarangan”, rebooted and then tried backup again. It seems to have solved the problem. Now backup is running in acceptable speed.