Hello. I know this conversation seems to be close, but thought I'd try to post here. I'm having a problem unmounting an external hard drive. I have a 2010 iMac with a 1.5 TB Seagate external hard drive I use for Time Machine as well as other backups. I cannot transfer files to/from this hard drive anymore, and Time Machine will no longer work. I can see the drive in Finder, but some times the folders appear to be empty of files, and sometimes I can see the files but cannot access. Disk Utility states the disk needs to be repaired, but when I try to repair the disk, "unable to unmount for repair" is stated. I've tried to unmount through disk utility as well as through Terminal. I've tried to unmount the entire disk as well as the individual partitions. Any suggestions would be great. Thanks.
Example of what I've tried in Terminal. (sorry if my computer speak is wrong. Not really a computer expert)
#: TYPE NAME SIZE IDENTIFIER
0: Apple_partition_scheme *1.5 TB disk1
1: Apple_partition_map 32.3 KB disk1s1
2: Apple_HFS HLH1.5TB 1.5 TB disk1s3
Macinto9e3bfb3c:~ howardhonig$ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_HFS Macintosh HD 999.3 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: Apple_partition_scheme *1.5 TB disk1
1: Apple_partition_map 32.3 KB disk1s1
2: Apple_HFS HLH1.5TB 1.5 TB disk1s3
Macinto9e3bfb3c:~ howardhonig$ diskutil unmountDisk /dev/disk1
Unmount of disk1 failed: at least one volume could not be unmounted
Macinto9e3bfb3c:~ howardhonig$ diskutil unmount /dev/disk1s1
disk1s1 was already unmounted
Macinto9e3bfb3c:~ howardhonig$ diskutil mount /dev/disk1s1
Volume on disk1s1 failed to mount
If the volume is damaged, try the "readOnly" option