I just bought a Patriot 128GB class 10 MSD from Fry's Electronics a few days ago. It is exclusively for use in my Note 4, which Samsung states to be compatible with 128GB MSDs. I need to have 3 partitions:
1.90GB exFAT (advantage over FAT32 is larger file sizes over 4GB, which my stock modded TouchWiz ROM recognizes out of the box). I would love to use Ext4 for this partition, but it seems to be only mountable by AOSP/CyanigenMod-based ROMs, whereas TouchWiz ROMs cannot mount Ext4 on MSD without questionable/unreliable hacks. By default Android will only mount the 1st primary partition on an MSD, which is why it needs to have the largest size of the 3.
2. 2nd partition, 25GB formatted as ext4, which is for use with an app called Link2SD.FS must be ext4 because permissions and file ownership must be supported, which exFAT cant handle. L2SD allows to "link"/"bind" apps, odex/deodex files, app data/caches, etc to the 2nd partition, via symbolic links. This is mainly useful for games and other large apps.
3. 1.5GB Linux swap partition, not for use by the ROM/Android itself, but for use with running chrooted/jailed Linux installs (think of it as running a full Linux distro in a VM on Android).
Theoretically, this setup should be fine, but in practice I've found it be slow. Copying files to/from the 1st primary partition can take awhile, when I first set this layout up it took several hours to copy about 12GB of files from the phone's internal storage to Sd. Speeds ranged from less than an Mbyte per sec to 20. Apps linked to the 2nd partition oftentimes run sluggishly, hang for short durations, etc.
Partitions were created with a card reader on a PC via Gparted in Parted Magic. MBR was used. I also checked the alignment of the partitions via parted (CLI version of Gparted). All seemed fine. I dont think the SD is a counterfeit/bum, the Patriot brand is known for reliability, and Fry's isnt known to willfully sell knockoffs/faulty goods. Speed tests with various benchmark tools show the card runs at/near advertised speeds (with a margin above or below rated speeds, of course). I'm thinking this is a matter of improper alignment, not enough space at/before partitiin table start, I'm just not sure. I went with Gparted's default alignments when creating partitions.
I'm basically looking for MSD-specific partitioning advice, perhaps recommendations to use other filesystema if need be.
More info, probably not relevant:
Bootloader is unlocked, so I can install custom KitKat/Lollipop ROMs,AOSP ROMs, etc.
Latest TWRP custom recovery installed
Device is rooted with CF-AutoRoot and latest SuperSU
Rom is stock odexed TouchWiz 4.4.4 KitKat firmware released by Samsung, but with minor community mods like busybox preinstalled, zipaligned, etc. All stock Google/carrier/Samsung bloatware is present but can be easily removed
Custom kernel is installed, with support for execution of init.d scripts on boot (otherwise Link2SD wouldnt work), overclocking/underclocking, loop device support, SELinux security status is set to Permissive rather then Enforcing (Latter is KK default value as mandated by Google)