[iMore Question]

I am having an issue backing up my iPhone 4s, iOS 8.4.1 on my iMac running El Capitan. There is more than enough free space on HDD (1.58 TB to be exact), yet the iTunes return an error message saying it "could not back up" because there is not enough free space to save the backup.
Any ideas on why does this happen and what to do with it?
Thanks in advance

[Trees]

The articles below may help if you've not had a chance to try the suggestions before. From what I could tell in the Apple Support Communities discussion, others are running into what sounds like the same problem you have. There are some suggestions for how to potentially fix the problem in the discussion, but I have not tried them as I have not run into the problem.
https://support.apple.com/en-us/HT203271
https://discussions.apple.com/thread/4421434?tstart=0

[Larry Cook1]

I read once for the best way around this was to the download in itunes.

[lungdoctora]

I have had this issue on our iMac backing up My iPhone, my wife's iPhone and our ipads. Error message not enough memory to complete backups to the iMac. Plenty of memory, we have been troubleshooting this issue for months without success. I then download imazing program to try backup and this also failed, however I noticed a warning from Norton that part of backup was being deleted because it found a trojan zbot. After this happen the the backup fails both in tunes and in Imazing. By erasing the prior backups in the folder ~/Library/Application Support/MobileSync/Backup/ and turning off antivirus Norton problem solved. I suspect norton found fragments had a pattern of bits that matched a pattern that occurs in files that have a particular piece of viral code. Did a full scan of my system and not virus found. Backup now successful on all devices and with both programs.
I hope this helps others with similar issues
Dr. Aaronson

[kistent2014]

● upgrade iTunes and all Apple drivers to the latest version;
● reboot iTunes/iPhone/computer;
● rename the backup folder;
● change the backup path to another one;
● remove trash files in recycle bin;
● restore iPhone first....