Wednesday, 23 May 2012

Formatting FAT32 Volumes Larger Than 32GB & SD Card Alignment

For a long time, flash memory for mobile phones and portable audio players seems to have been stuck at around 32GB.  Many devices report their maximum supported card size as 32GB, but this didn't stop me buying a Sandisk 64GB Micro SD for my Galaxy S2 and playing around with it.

Samsung claim the Galaxy S2 supports a maximum of 32GB via it's Micro SD card slot, but as the owner of AndroidNZ found out, this wasn't strictly true.  He had tried the card in the device, and once I saw that it was working, I decided to take a punt and buy one for myself.

64GB Micro SD card working flawlessly in my Galaxy S2, which claims to only support up to 32GB.

Initially you may run into some difficulty.  When I inserted the card into the phone, the phone said that the card is damaged or unreadable.  It appeared that my card shipped unformatted, which meant it had no filesystem.  The first challenge was to format the card in a filesystem the Galaxy S2 could read.  I tried the Linux filesystems first such as EXT2, EXT3 and EXT4, as the default filesystem FAT32 has a 4GB maximum filesize limitation, and I intended to use my phone as a portable HDD too (very useful for transporting or downloading Linux ISOs if you are caught out with a dead computer).

I found that with the Galaxy S2, EXT2, EXT3 and EXT4 were not supported, which was quite annoying and odd since that the internal memory of the Galaxy S2 uses EXT4.  So why can't it mount EXT4 SD cards?  I had also tried mounting external NTFS HDDs before with no luck, so I knew not to bother wasting my time with that.  I also tried exFAT but still no joy.  Hopefully since the Galaxy S3 supports exFAT the code will be retroported to the S2 (everything crossed).

The card even works on my 2008 Nokia N96!

So unfortunately that left me with FAT32.  For whatever reason, my S2 refused to format the card (but since I formatted the card, my phone will do it no problem now) which meant I had to do it on my computer, and immediately I ran into an old problem.  You see Microsoft impose a 32GB limit on partiton sizes for FAT32 in recent operating systems (XP onward I believe), despite the filesystem supporting partitions up to 2TB on paper.  My only guess is that Microsoft wanted to push NTFS as the dominant filesystem since it's a lot more robust.  I had tried formatting by right clicking the drive in "Computer", through launching diskmgmt.msc via the command prompt, and then even resorting to the CLI format utility, diskpart.  None of which would allow me to create a FAT32 partition of 64GB.

Fortunately, third party partitioning software will allow you to create FAT32 partitions in excess of 32GB, so it was time to find an alternative.

For simple partitioning, I found Easeus Partition Master which has a free version with all the functionality we need (for my final formatting, I eventually decided to use some tools supplied in Linux, but I'll come to that later as it concerns aligning the SD card too).  If you are a little more experienced with computers, or have used Linux in the past and are familiar with the filesystem structure, you could also use a GParted Live CD which boots into a basic version of Debian with the GParted program which is simple to use.

Additionally you could possibly use a Windows 98/ME boot disc or Windows setup disk to get into DOS and run fdisk.  Unfortunately even though I was able to find the boot disk files online, they wouldn't run within 64-bit Windows - they might possibly work within DOSbox though.

Partitioning With Easeus Partition Master
For the purpose of this tutorial I will be using an old 32GB Micro SD card as I have already formatted my 64GB and loaded it up with music and stuff.  The process is identical, but the reported volume sizes will be different.

Upon launching Easeus, you will be shown a screen like the one below.

Note the disk sizes, so that you don't accidentally delete partitions on your HDD!

Easeus is really easy to use, but here's a quick run down for those who might not have partitoned a disk before.

1) Upon opening Easeus, check to see if your SD card has any existing partitions.  The one in the screenshot is blank.  If you have existing partitions, select it by clicking on it, then right click and choose Delete Partition, then click Apply in the top left hand corner.

2) Right click the Unallocated space of the SD card you wish to format and click Create Partition.  Change the default settings to match the screenshot, so we are creating a Primary partition in FAT32.  You can adjust the space used if for some reason you want to create multiple partitions, but in general you just want to select the maximum amount.  The drive letter is not important, so leave that as the default.  Once you are done, press Ok to go back to the main screen.

The first part of creating a FAT32 partition
That's all there is to it, but if you would like to experiment with different cluster sizes which can improve write speeds, perform the final step below.

3) To change the cluster size, right click the partition and select Format Partition and choose a cluster size from the drop down menu.  Press Ok to go back to the main screen and press apply to write the changes.  In general, the larger the disk size, the larger the cluster size you would use.  Using larger clusters can help improve transfer speeds, but at the cost of disk space efficiency.  What this means is that files occupy space on the disk to the nearest cluster size.  So a 12KB file on a disk with a cluster size of 16KB, will use 16KB on that disk, or if the cluster size was 64KB, then that same 12KB file will occupy 64KB.

Aligning the SD Card
If you are comfortable with Linux and command line tools, then we can improve the speed of the SD card by aligning it.  The theory behind this is that SD cards erase/write 128KB blocks which means even if only 10KB in that block changes, the whole thing needs to be re-writtent.  Most formatting tools don't seem to be aware or care about how SD cards work and just format the FAT32 filesystem in the usual way, however better performance can be achieved if the File Allocation Tables end at the border of a block, with the data starting at a new block, rather than some of the FAT using part of a block and the data starting in that same part block.  This makes it easier for the SD card to write full blocks more often than it would if the partition was unaligned.

I found that with my SD card unaligned, I would get write speeds averaging around 6.5MB/s, but once aligned it would manage a consistant 9MB/s, and higher with large files.

Unfortunately I do not know of any SD card alignment tools for Windows when it comes to FAT32, so we will be using a Linux Live CD for this, but if your device supports exFAT, then I've found the official SD card formatter to give really good speeds.

We first need a Linux environment, you maybe already run some linux distro, but if not we can download a Live CD which runs the OS from optical media without installing anything.  I use Opensuse

Here is a link to the original thread.  The guide I will post will pretty much be a simplified version of this based on my own experience as I found the guide a little bit cryptic at first.

Partitioning The Card
1) First, insert the SD card so that Linux detects it and allow it to mount.  If it doesn't mount automatically, you can open the file browser and browse to the card as this will cause it to be mounted.  You may need to have a filesystem on the card beforehand, so you can just format it to NTFS or something in Windows as a temporary measure.

2) Open a terminal window from the progam menu and type:
df -h
df is the disk free command, which shows you the available space on your mounted drives, and the -h switch for "human" readable information, such as MB and GB rather than just bytes.
There are a few pieces of information we need here.  Locate your SD card by its capacity in the list, and make note of the Filesystem and Mounted on columns.

As you can see, my SD card is listed under filesystem as /dev/mmcblk0p1 and under mounted on as /media/15F4-1F1D

I should explain briefly about how Linux's filesystem works.  /dev/mmcblk0p1 is actually referring to a partition on the disk, and the disk itself is known as /dev/mmcblk0 - as you may have guessed, Linux simply suffixes p1, p2, p3 etc to the device name to denote partitions on a device.  /media/15F4-1F1D is the mount point and is the Linux equivalent to a drive letter, eg C:

3) Next we need to unmount the drive.  In the terminal window type (replacing the mount point with whatever your drive is mounted as when you typed df -h):
umount /media/15F4-1F1D

If you don't want to type the whole thing, you can start it off and press Tab to complete it automatically.  If the unmount was successful, you are returned to the prompt.  You can check it was unmounted by typing in df -h again and confirming that it is not in the list.

4) Now we need to change the drive geometry in order to make the 128k easy.  Flash memory works differently from harddrives and do not have physical, sectors tracks or heads, but it still uses that information to organise data.  The aim is to find a combination of sectors, tracks and heads that is evenly divisible by 128KB (131,072 bytes).  The suggested geometry of 224 heads and 56 sectors does that (224 heads x 56 sectors x 512 bytes per sector / 131,072 bytes = 49) whereas the default value (255 heads x 63 sectors x 512 bytes per sector /131,072 bytes = 62.75) does not.
In the terminal window, type the following:
su (then press enter, this enables super user mode, or admin)
fdisk -H 224 -S 56 /dev/mmcblk0

fdisk is the partitioning program, -H sets the number of heads and -S sets the number of sectors.

To confirm this worked, press p to get a list of the partitions and device properties

4) While still in fdisk, we will create the FAT32 partition.  To do this, type the following at the prompt:
d (then press enter to delete any existing partitions - if you only have 1 it is deleted automatically, otherwise you are prompted to enter the number of the partition)
n (then press enter to create a new partition, then select primary partition and then enter through the other options).
x (to enter expert mode)
b (to change the beginning of the data, then select partition 1 and set the start to 1)
r (to return from expert mode)
t (to set the partition type, enter c when prompted for FAT32)
x (to enter expert mode again)
b (to set the beginning of the data to 256 for partition 1)
r (to return from expert mode)
w (to write the changes to disk

You may press q at any time to quit without saving changes.

5) Finally we need to create the aligned FAT32 partition.  We first need to find out how big the FAT tables are going to be, so we can manipulate the size of the tables to finish at the end of an erase block (the 128KB blocks we keep talking about).
At the terminal window, type:
mkfs.vfat -F 32 -s 32 -v /dev/mmcblk0p1
Then press enter to format.  Once done, you will see something like below, giving a read out of the disk.  The line we need is the FAT size which tells us how big a single FAT is (there are two on this disk).

6) We then need to calculate the size of the FAT in bytes, to see if it will end on a whole erase block or not.  What we do is:
FAT size x No. of FATs x 512 bytes per sector / 131,072 = No of erase blocks
In this instance we would have:
14,976 x 2 x 512 =  15,335,424 / 131,072 = 117
Now if at this point the number of erase blocks is uneven, we need to pad that out to fill the erase block.  Simply round up your last result to the nearest whole number and reverse the calculation.

No of erase blocks x 131,072
Which gives us:
118 x 131,072 = 15,466,496

Now we subtrack the original FAT size in bytes, from the erase block aligned FAT size in bytes, then divide by 512 to give us the number of sectors difference to be used as reserve sectors.  This is essentially expanding the amount of space allocated to the FAT in order for it to finish on a complete erase block, so the data starts on a new block.

15,335,424  - 15,466,496 / 512 = 256 reserve sectors

7) Now we know how many reserve sectors are needed to ensure alignment to the erase blocks, we can continue to format with the correct information.
At the terminal window, type
mkfs.vfat -F 32 -s 32 -R 256 -v /dev/mmcblk0p1

The switches used are:
-F 32 (for FAT32)
-s 32 (cluster size expressed as sectors, so 32 x 512 bytes = 16KB clusters)
-R 256 (number of reserved sectors)
-v (device to be formatted)

Once that has completed, you can mount the drive to transfer items to it, or simply remove it and go back to Windows, or use it in your device.


  1. Yup, it works. Write speed doubled. Thanks!

  2. Excellent, thanks for the feedback :)

  3. Did you try NTFS? Some roms support it, maybe not stock.. i don't know

    1. I tried NTFS on the stock ROM with no luck. Sure, I think some custom ROMs support NTFS (maybe cyanogenmod?) but since it's currently on contract and I'm happy with the way it is right now, I just wanted it to work on stock.

      The advantage is that I can take my card out and put it in any other phone, so if a friend wants to copy a video or something, he can do no problem.

      The other thing is that it works better for stuff like car stereos or maybe docks that can read from the SD card - as virtually none of those external devices support NTFS.

      exFAT is the next best option, but it still has limited support in other devices at the moment.

  4. So the problem then still won't be able to transfer files bigger than 4Gb right? I've been looking all morning to find a way to get my 32Gb SD to transfer files that are larger than 4Gb because i torrent big files and would like the possibility to download them on my phone directly. I've been torrenting files under 4Gb with no problems.

    The only option i see so far is the NTFS route because my phone is running a custom rom. Now i simply gotta figure out how to achieve that because when i try formatting it, it won't give me that option. Any opinions?

    1. Hey, sorry for the late reply.

      Sure, if you have a custom ROM then you may be able to use NTFS or EXT3 or EXT4. I'd go with NTFS though since it's more widely used.

      If you can get a card reader for your SD card, plug it in and when Windows recognises, go into Computer (for the list of drives), right click it and choose format. You should be able to pick NTFS from there, if not then follow the bit of a guide I wrote earlier for formatting to FAT32 using Easeus, but select NTFS instead.

  5. Thank You; it worked in reformating my 64 GB SDXC card so my phone can use it.
    I spent ages on other methods; but Easeus came thru in the end.

    "Apply" button confused me in top left, as it is not noticible, and it seems commands have already registered and failed, silly me.

  6. I really appreciate this. Just installed my 64GB card without any problems.


  7. Glad to hear it guys. Hopefully it won't be long now and other filesystems will start to be supported in Android for removable media.

    Although this method works, the problem still remains that the largest filesize you can have on FAT32 is 4GB.

    Which is a shame because it would be nice to be able to use my phone as a portable HDD when I go to a friend's house etc.

  8. Hi!
    It's probably a silly question, but do you know if this would work on a Samsung Galaxy S Blaze? (although it's "Galaxy S", it's actually more recent than the Galaxy S2)

    I just bought one (it hasn't even arrived yet) and I'm looking for a memory card, but I'm afraid the 64gb might not work...

    Thanks a lot!

    1. I can't say for certain if it will work or not. This is something you kind of have to take a gamble with. That said, the odds of the gamble paying off are pretty good.

      I know that this method works with my S2, a friend's Xperia Z, and as I mentioned earlier on, my old 2008 Nokia N96 which was running Symbian!

      So personally I see no reason at all why it wouldn't work, but I don't want to say it does, just on the very small chance that it might not.

      I mean 2008 is really really reaaaaly old as far as mobile phone technology goes, and it worked fine on that. That phone has 80MB RAM? A 320x240 screen and a 264MHz CPU, so that gives you an idea of what we are talking about.

  9. This is fantastic, thanks. I'm transferring 32GB from the old phone to the new phone and transfers are happening more than twice as quickly. Frankly I was just looking for instructions for formatting beyond 32GB with mkfs.vfat, and I got this as quite a bonus. I'm sure it will return benefits for years.

    I'm not sure how well these things transfer between lot numbers, but FWIW, this is on a SanDisk "Ultra" 64GB SDxC Class 10 "UHS-1" and I got a reserve block number of 50.

  10. Just wanted to say thanks for the guide, just got my new 64GB card working in my S2 with your assistance. For the record it's the same card type as Bill's above, Sandisk Ultra microSDXC UHS-1 Class 10 (this one:

  11. This comment is coming from the US. I'm using the same card as tmbrichards and Bill McGonigle: Partitioned to FAT32 using Easeus, and it worked flawlessly on my Boost Samsung Galaxy S2. Can't believe how easy it was, and now I have double capacity! Thanks for the link!!!!!!!

  12. i have a dual system tablet win10 and android 4.4
    win10 reads the 64gb card (after some tweaking) but android only can handle a fat32 32gb cards.
    i can use your trick to format my 64gb with fat32 to be read by both, but iprefer 2 partitions: one fat32 for the android and another exfat or ntfs for windows without the 4gb limitation. is it posible?

    1. I don't see a problem with creating 2 partitions. You could have a 32gb FAT32 partition for Android and then a 32GB NTFS or whatever for Windows. Obviously any FAT32 partitions have the 4GB file size limit, so you'll be stuck with that in Android, but your Windows 10 install should use the NTFS features no problem.

      Only other thing I could think of is if you could somehow update the Android install. I think newer versions support Exfat, in which case you could probably make one large 64GB exfat partition that both installs can access. It's just a case of experimenting.

  13. i already did. thanks. works fine. but every time i return from android to windows windows do not recognize the sd card until after troubleshooting to fix it. i guess its about upgrading the sd card driver to a non compatible one. i cannnot think of a way around it. Is there a way to block win10 from automaticaly updating drivers?? i am afraid upgrading the android software to this chinese tablet might be an issue

    1. I'm not really sure. Have you tried unmounting the SD card in Android before you switch to Windows?