Hi, You could disable the auto synchronization of the stack firmware and update each member of the stack and reboot, but this is not recommended or supported and still could interrupt the network, it is better to do the auto update and have the downtime to reset the whole stack at once. no boot auto-copy-sw is the command to disable it. ftp://ftp.dell.com/Manuals/Common/powerconnect-7024_Reference%20Guide_en-us.pdf page 1356 
I'm about to execute a firmware update on a stack of 2 PowerConnect 7024 switches. These switches are for our iSCSI SAN, so ideally I'd like to reboot 1 at a time. Is this supported? The 'reset' (terrible name!) option is ALL, 1, 2. All being the whole stack at once, 1 being the 1st sw etc etc. I'd like to reboot 1, see it come up, then reboot 2. Is that supported? It would be maybe 30 seconds of the stack members having a different firmware version which I know is NOT supported...
Firmware update on PC7024 Stack