Jtdylktuy

Is it possible to create RAID 1 with RAMDisk and SSD in OSX?

Something like:
Boot Mac, OSX-Partition will be loaded from SSD in RAMDisk. Boot to RAMDisk and use it like any other system-drive. Because of RAID 1 (--write-mostly/write-behind) anything done on RAMDisk will be persisted to SSD. So if I power off the Mac everything will be persisted on SSD and can loaded again during next start...

For better experience the most used applications could be installed to that OSX-System-Partition (SSD) which will also be available in the RAMDisk.

Of course there will be a second "data" partition on the SSD for all the other stuff.

How can I achieve the described setup - is it even possible with OSX? Which Bootloader can I use (Grub?)?

From comments, here's the bones of how I do a RAMDisk setup & copy back.

It's not the complete structure, so won't compile as it stands [there will be many missing declarations, as I have a whole set of other structures before I get to this bit, that aren't generic enough to be worth copying in], but gives the routines for creation, copy out & copy back. Save it as an application & launch this instead of your app.

There's also no provision in it for telling your app to use it - that, for me, is a separate structure just using the app's prefs & some —settings instructions at launch.

It's also set to cover if a mismatch occurs - that's because I have several versions of that particular app, & caches should not be mixed. You can probably leave that section out.

-- RAM Disk setup

        set copying to 0

        if not {exists disk RAMDisk} then

            set VolumeName to RAMDisk

            set SizeInMB to 1024

            -- can choose size using this dialog

            --display dialog "RAM Disk Size:" default answer SizeInMB buttons {"OK", "Cancel"}      

            set NumSectors to ((2 * 1024 * SizeInMB))

            set DeviceName to do shell script "hdid -nomount ram://" & NumSectors

            tell current application to do shell script "diskutil eraseVolume 'HFS+' '" & VolumeName & "' " & DeviceName        

            set foundDisk to false

            repeat until (foundDisk = true)

                if exists disk RAMDisk then

                    foundDisk = true

                    delay 1

                    -- do copy...   

                    duplicate full_path to disk RAMDisk

                    exit repeat

                else

                    delay 1 -- waiting for RAM disk to appear, if it's slow

                end if

            end repeat -- end disk wait

        else -- if RAMDisk exists already           

            set p to (folders of disk RAMDisk)

            if (exists folder cache_name of disk RAMDisk) then

                if p is {} then -- disk's empty

                    duplicate full_path to disk RAMDisk

                end if

            else -- if not (exists folder cache_name of disk RAMDisk) then

                display alert "RAM Disk contents are from a different version.nErasing first..." giving up after 4

                try --deletes entire contents of RAMDisk, doesn't throw to Trash

                    --Folder in Trash can still cause "disk full" error.

                    --'quoted form' in shell scripts (unix) enables spaces in file names (ie RAMDisk name)

                    tell current application to do shell script "rm -rf Volumes/" & quoted form of RAMDisk & "/"

                end try

                duplicate full_path to disk RAMDisk

                delay 2

            end if -- end cache name check

        end if -- end RAMDisk check



(*at this point, launch your app, the script will sit & wait for it to quit*)



-- after app quits, copy back & tidy up

        display dialog "Quitting or just restarting 'app'?" buttons {"Quitting", "restarting"} ¬

            default button "Quitting" giving up after 30

        set thebutton to button returned of result as string

        if thebutton is "Quitting" then



            set toCopy to true -- to test for copyback

            if folder backup_location exists then

                display dialog "Safety folder already existsnDelete & continue copy-back or just quit?" buttons {"Delete", "Just Quit"} default button "Delete" giving up after 30

                set thebutton to button returned of result as string

                if thebutton is "Delete" then

                    delete folder backup_location

                else

                    set toCopy to false -- will bypass copyback

                end if

            end if

            if toCopy is true then

                -- set a backup folder name before copying

                set name of folder full_path to cache_name & " - old"

                delay 1

                duplicate contents of folder cache_name of disk RAMDisk to folder custom_caches_base_path

                delay 1

                delete folder backup_location

            end if

        end if -- end quit sequence