Backing up 8TB - how long with this take with Time MAchine?

TM will probably never finish.. by the time it backs up it will need to start again.

TM is not really going to handle 8TB very well and as most of that would be file storage.. you shouldn't use TM for it.. use a standard backup software.

There is no way we can answer your question.. none.. as you haven't given us any data whatsoever to make a calculation.. other than backing up 8TB..

You would need to do tests yourself.. copy a large typical folder to the backup store.. say around 500GB.. so you are copying both large and small files.. and time it.. then x16 for 8TB..

This is utterly dependent on disk speed in the computer, in the file store, and in between network speed. I cannot even guess which is the rate determining step because we have zero info.

Some very rough guesses, using an Ethernet connection, it might take 1 TB to take roughly 36 hours, so 8 TB would be roughly 300 hours or about 12-13 days or 2 weeks

Wireless might be 4-5 times longer or more depending on connection and other activity on the network.

doigjo wrote:

ok - what I have is an 8TB G RAID drive as the time machine - the working drives are 2 x 4TB G RAID drives and the 1TB drive inside the iMac - all external drives are running Firewire 800 - drives are hi-performance hitachi drives spinning @ 7200 and transfer files @ "up to 200MB/sec" (eSATA) ... I guess my real question is : I started the process 24hrs ago - and time machine doesn't give a lot of info - other than 'in progress' or 'calculating size'

Something is wrong. How is this RAID box connected to your Mac? (You've posted in the Time Capsule forum, so we're not sure just what your setup is).

But if this is the first backup, copying should start very quickly.

A clue may be lurking in your logs. Use the widget in #A1 of Time Machine - Troubleshooting to display the backup messages from your logs. Locate the backup in question, then copy and post all the messages here.