2008 iMac upgraded to Mountain Lion now boots slowly?

Question

We have an Early 2008 Aluminium iMac. 2.4 GHz Core2 Duo, regular HDD. I think it came with 1 GB of DDR2 RAM but we upgraded to 2 GB. It originally came with Leopard but we upgraded to Snow Leopard on short order. So everything was good, maybe when it was brand new it would be ready to use in 25-30 seconds and after four years it would usually boot and be ready to use in 30-45 seconds. Pretty quick, maybe due in part to a hard drive that was mostly empty (don't know if that matters).
But then when Mountain Lion came out, I wanted to upgrade. I swapped out the 2GB of RAM for 4GB, ran the installation tool, and that was that. However, ever since then, boot time takes at least twice as long. (Both takes longer to get to desktop and takes longer for desktop to be ready for me to launch apps.) I knew it uses a little extra RAM but I didn't think it should be so bad for performance. I've reset PRAM and repaired permissions and all that boring stuff already, but it doesn't help.
I suspect there is just something that could be fixed so it doesn't take so long, like some caching setting or something (I really have no idea what I'm talking about) or that if I do a fresh install it *should* go back to booting in 30 seconds. However I don't want to spend half a day reinstalling and restoring on a hunch. So what are your suggestions?
I also plan on upgrading to OS X Mavericks in the fall as it seems like it includes performance improvements (not sure if it'll matter for boot though). Might upgrading to Mavericks "fix" some messed up setting that slows down boot time? Or would it not make any difference? Or would I have to do a fresh install when I upgrade to Mavericks to avoid a slow boot time? Or should I just wait till I want to upgrade and then do the whole fresh install and restore files/apps/settings from my time machine backup (or better to do manually)?
I'd like to add also that I have a MacBook Pro with an SSD and 4GB DDR3 RAM that came with Lion, and doing the same kind of upgrade process to ML as I did on the iMac didn't effect boot time on the MacBook Pro (it's still about 15 seconds).

Answer 1

Hello Mac OS XP,
While your iMac is within the scope of supported machines for Mountain Lion, it is pretty far down the spectrum. Every new OS will require more resources than the one before it wether thats processor, RAM or graphics power. I would personally keep a machine like that on 10.6 Snow Leopard for best performance. Anyway, it cán handle Lion or Mountain lion but it will perform slower than it did under Snow Leopard.
That said, upgrading an OS that has been upgraded in the past and then skipping a version to the latest OS, there are usually some complications. There are a few things you can try to get some performance back but at this point i do recommend backing up your machine, re-format the drive, install a clean copy of Mountain lion and then restore your data.
You have tried the permissions repair which is always a good first step. (backup before you continue) Next restart your Mac, hold down the Option key as soon as you hear the startup chime and select your recovery partition as your startup disk when it pops up on the screen. From there, open disk utility and instead of repairing the permissions, run a Verify on your hard drive (and a Repair, if needed). Quit Disk Utility and the Recovery window and you can select your main partition as startup disk again and restart.
If repairs or modifications were made by Disk Utility, it may actually take even longer to start up now but that's just the first time, if you restart again you'll see if you actually gained performance.
If that did not work, i'd start over. You may spend more time trying to figure out and test different fixes than it would take to just re-install and enjoy a clean OS.
While Time Machine is an option, in this case i would Clone the drive with a utility like SuperDuper. Personal preference and when it comes to multiple OS upgrades etc. i find it more reliable than Time Machine which is pretty complex in it's own way. A benefit of a cloned drive is that it's bootable. If something goes wrong or your internal drive breaks in the future, you can start up from the clone drive and just keep on working (it'll be slow if it's a FireWire drive and even slower if it's USB but you'll be able to work and access your data).
Someone else may come along to suggest other things to try so if you are not in a hurry i'd give this post a little more time to be seen by others. I would make that clone or time machine backup, your choice, now though as most suggestions and recommendations you'll get are pretty invasive.