i don't use mac, and most regulars here do not either. i can give some input based on the hardware. i think the 21" screen size is just too small for working with creative software. there are other limitations to the 21" models i will point out in the hardware sections below. if these machines will be split up and only have to handle some of the software, like only photoshop/illustrator, then it might make sense to have multiple configs. i take it the gtx 680's are in the small tree server? if you are actually using the gtx 680 with the mac pro's via e-gpu, then it may be possible to use those to with the imac's. if you weren't planning on doing this already, it would be good to order one or two machines with the configuration(s) you think will be best and test them out, before committing to ordering bulk.
cpu: the entry level 21" imac with the 1.6ghz i5 should be skipped, its using a laptop i5 cpu and is much slower than the desktop i5's in the other models. photoshop and illustrator would probably be ok with a desktop i5. audition might also but would depend on how many and which vst/plugins are being used, and how many audio tracks. AE and premiere will be the most demanding and may benefit the most from the i7. i've heard the imac can overheat and thermal throttle the i7 during extended max cpu usage sessions like exporting/rendering.
ram: you might already have an idea of how much memory the machines would use, based off the current mac pro's. if not, AE and premiere will likely need the most, between 16-32gb, while the rest of the software may be fine with 16gb. only the 27" holds up to 32gb (4x8gb), while the 21" imac's can only hold 16gb (2x8gb) max. i think memory upgrades are only simple with the 27" imac. third party apple compatible memory is also available, which is cheaper than apple branded memory. with the 27" imac, if you need to save costs you could start with 16gb (2x8gb) and add more later if needed, or start with the default 8gb (2x4gb) and add in 16gb (2x8gb) of third party memory for a total of 24gb.
storage: it would be nice to use a flash drive instead of the 7200rpm hdd or fusion. how large will depend on what it needs to hold locally, like any cache or any project files etc. if everything is stored on the network, the small 256gb flash drive may be enough. if budget is tight and the cache and media files will be on the network, the fusion drive might be a good compromise over the 7200 rpm hdd. i think the drive is buried inside the imac's and are very difficult to upgrade later. usb 3 or thunderbolt external storage would be an easier upgrade.
gpu: if the premiere or AE projects will be using alot of gpu fx or third party gpu plugins, the 27" imac with the R9 395 would offer more power to handle those. if using just a few gpu fx, the M380 or M390 would help cut costs. i think there are some plugins for photoshop that can also benefit from a good gpu, but i think those plugins are kinda rare. if planning on doing any 4k projects the extra vram on the R9 395X 4gb may help. the 21" imac only has intel graphics, which wouldn't be good for premiere or AE. an e-gpu via thunderbolt may allow for a gpu upgrade later if needed, or also allow for nvidia gpu with cuda if software requires.
Thank you so much for sharing your thoughts. All are true, valid and are in sync with what Apple is telling me. It gets expensive quickly and as you pointed out-we do not store everything on the server so local storage capacity is a feature we need. The
Graphics card is also recommended by the team. Sorry the NVIDIA Cuda technology is not available. We have enjoyed its performance on the Mac Pros for a year now.
I think our configuration could be:
iMac 27 inch with Retina Display(the guys are used to running 2 monitors mostly)
4Ghz Quad core Intel Core i7
2TB Fusion Drive
AMD Radeon R9 M395x with 4GB onboard RAM
Apple Care for one year.
This seems to be in line with your descriptions as well. I found the 21.5" model to be an underperformer also as you pointed out.
The only puzzle I need to solve is the Fusion Drive. I am thinking that it has the advantage of storage space and some quick availability when in use with After Effects and Premiere. However since it is the system drive all cache, temp auto saves and waveforms, etc. will be placed on the same drive. I wonder how that might effect performance 6 months down the line? I don't think we will be using external local drives but definitely connected to the server for video files.
i think the 2tb fusion drive has 128gb of ssd/flash in the 2tb hdd. i'm not sure if the 3tb fusion drive has more flash or the same amount. if the cache files from the adobe software will be written and stay on the flash for the current project it might be ok, otherwise once its on the hdd part of the drive it may impact performance. that also assumes that active cache files, and whatever else the fusion drive see's as worthy of the flash memory, will take up less than 128gb of space. if most of the data, like large video files, will be on the server it makes some sense to go with a smaller but 100% flash drive for the same cost. if needing more space locally for cache, upgrading to the 512gb flash would cost about as much as adding an external ssd. its not until the 1tb flash drive that an external ssd's make much more sense for cost savings.
as far as 6 months down the road, that mostly depends if you think the storage performance or capacity needs will change. unless you have an idea of those needs, leaving it open to add external drives would give more flexible options later when the demands are better known. the tidbit of info i can give about performance on the current drives would be that the drives will loose some performance as they fill up with data, more so with hdd's than flash/ssd.
installing the third party compatible memory could cut $350-450 off each machine, depending on how much memory you want to add.
I'm not sure how Premiere or After Effects for that matter will use the flash drive in the Fusion set. I know that the editors clutter their desktops with downloaded material and don't even use CleanMyMac when I gave it to them. So having a large hard drive seems necessary. But if its the system drive and the storage drive as well it may in time get slower. Our MacPros have a seperate internal drive available for caching and such but the iMac does not. I was judging the Fusion drive as the best of both worlds but its use may get lost in translation. Certainly adding an external Thunderbolt or USB3 drive could be an easy solution. I just love the MacPro 2009 design with its flexibility and adaptability. I can't understand why Apple did not maintain it as a standard for updating thru the years.
Thanks for the response.
the downloads and other files the editors have, if less frequently used should be moved to the hdd part of the fusion drive. but something that was recently downloaded may also be competing with cache for the limited flash space of the fusion drive. using the fusion drive plus an external usb drive for cache would help keep performance consistent and allow space on the fusion hdd for their misc downloads etc. if there is storage space on the network, like user account assigned space, for them to keep their downloads and misc files, that could remove the need for larger capacity drives locally.
i'm not sure how this would be done in mac os, but there might a way to write a script that runs at login or scheduled at some maintenance time, that would run CleanMyMac or simply delete old files in the cache and any temp directories. as long as its deleting only old files, say over 2 weeks or a month old, the adobe software shouldn't have to rebuild any cache used by active/current projects. that would remove the need for the users to do anything on their end.
I'm now wondering if the Fusion Drive would just be getting in the way and bottlenecking and a standard Hard Drive for the one and only in the iMac would be better for me. I can add an external drive at any time and assign it to Premiere's use but I am trying to be cost sensitive in preparing a system with possibly 6 workstations.