Dan Pritts wrote:
no it doesn't. It could delay the sync until after the first boot or until later in the install process.
Actually, it doesn't need to do the sync at all. The reasoning being that parts of the disk you did not write to, should never be read (under normal circumstances). One version of Fedora (not sure if it was Core 1 or 2) was not syncing mirrors created during an install. I guess some people got bitten by it, so they reverted it back to the old safe way.
Because it's trying to do the sync at the same time that the installer is trying to install packages, so the disk heads have to seek all over the place to try to service the competing I/O requests.
A much better approach would be to delay the sync until after the first boot, or to have the installer give you the option to do the sync after the packages have been written to disk but before the reboot.
I've noticed this only on unsupported IDE controllers where disks were accessed in PIO mode. On anything else, the slowdown due to syncing was minimal. Anyhow, not syncing disks right away is asking for trouble. Data consistency is concern number one. Speed is somewhere around the end of the list.
Anyhow, in your case you could always do normal install on one disk, and build mirrors after installation is done. Although, option to only half-build mirror (specify only one submirror) during install for cases where second submirror is not available during install would be a nice option.