Flash cards getting smaller?

Status
Not open for further replies.
Joined
Oct 30, 2002
Messages
42,358
Location
Great Lakes
Over the years, I've bought a number of various 32 GB memory cards (SD, micro SD, USB stick, etc.). When formatted, actual usable storage space was around 29.7 GB, which is fine considering that manufacturers equal 1 GB to 10^9 bytes for storage purposes.

Now I recently picked up a couple of SanDisk Ultra 32GB UHS-I/Class 10 Micro SDHC cards. Actual usable space: 28.7 GB. What kind of games is SanDisk playing?
 
Newer Flash drives have load-managing software built in (on a hidden partition). Essentially the load management insures files are written to a new area of the drive each time because flash memory has a limited number of write cycles before it fails. So the software insures the entire drive is written to, before it goes back and starts re-writing on an area previously used.

On a magnetic HDD you can write to the same area multiple times without issue. On a flash drive without load management, it will write similarly as a magnetic drive, which reduces overall drive life.

As a result, the flash drives last longer but that hidden partition eats at capacity.

Note that this also affects security ... you can't erase a previously written area on a load-managed flash drive; the load management prevents the overwrite if there are under-used areas available. So data is readable for a long period before it's over-written. On a magnetic drive, you can securely erase specific areas (basically, over-write with random 0's and 1's); that doesn't work on a flash drive as your attempts to over-write are just written elsewhere instead of over-writing the area you want to securely delete.

So, it's added hidden partitions that reduce overall capacity, and *reduced* security on flash memory. If you want security on flash drives you need to encrypt the entire drive.
 
Last edited:
Originally Posted By: spasm3
When i saw the title, i was thinking, I didn't know they still made flash cards.


The Original Memory by Hasbro!
 
Last edited:
If they're formatted as Exfat instead of FAT32, that could also make a difference. Different file systems will suck up a different amount of space to keep track of everything.
 
Originally Posted By: spasm3
When i saw the title, i was thinking, I didn't know they still made flash cards.


Me too!
 
Originally Posted By: rslifkin
If they're formatted as Exfat instead of FAT32, that could also make a difference. Different file systems will suck up a different amount of space to keep track of everything.

All of the ones I mentioned were formatted as FAT32.
 
Originally Posted By: Johnny2Bad
flash memory has a limited number of write cycles before it fails.

Does this phenomenon also affect solid-state "hard drives"?
 
Originally Posted By: Tegger
Originally Posted By: Johnny2Bad
flash memory has a limited number of write cycles before it fails.

Does this phenomenon also affect solid-state "hard drives"?


Same technology in those Solid State Drives (SSD). With data management, a SSD has a similar expected lifetime as a conventional magnetic Hard Disk Drive (HDD), so there is no reason to panic.

All HDD's have hidden partitions as well, built in by the drive manufacturer. As areas of the drive fail, areas of the hidden partition are used to replace the failed areas. The bad areas are "mapped out" so that no new data will be written to the bad areas. The process is seamless to the user, so most people are unaware this is going on.

Drive failure is progressive and essentially relentless.

SMART-enabled Hard Disk Drives monitor the rate of failure and once a certain threshold is reached, will trigger a warning that the drive is about to fail. Again, this is technology built into the drive by the manufacturer.

All drives fail, eventually. That's why a backup strategy is always recommended.

At one time it was common for "server class" drives to be sold to commercial entities; they were more robust but cost much more than "consumer class" drives. Google pioneered the use of consumer grade drives, with backup strategies, in servers, as their tests showed the cost savings made that strategy effective.
 
Last edited:
Thumb drives are formatted in FAT32 for two reasons.

The first is that for smaller capacity drives, the limitations of the FAT32 file system are lessened.

The second is it's the only file system that is both readable and writable by all Operating Systems ... Windows, MacOS, UNIX, Linux, and the 300 or so other, less common OS's (Sun Sparc, Sun Solaris, Google Chrome, etc).

Unlike FAT32, Microsoft has not released the full specification for NTFS (and it is unlikely they ever will), so other OS's can read, but not write, to NTFS. So FAT32 is the only universal disk format, since other universal candidates, such as Linux's ext2, are very unlikely to be incorporated in a Windows OS.
 
Last edited:
Originally Posted By: Johnny2Bad
Unlike FAT32, Microsoft has not released the full specification for NTFS (and it is unlikely they ever will), so other OS's can read, but not write, to NTFS.

I've got an external NTFS drive connected to my Ubuntu Linux box. It can write to it just fine.
 
Originally Posted By: Quattro Pete
Originally Posted By: Johnny2Bad
Unlike FAT32, Microsoft has not released the full specification for NTFS (and it is unlikely they ever will), so other OS's can read, but not write, to NTFS.

I've got an external NTFS drive connected to my Ubuntu Linux box. It can write to it just fine.


Yes, there are Open Source and Proprietary solutions. I have no problem dealing with NTFS on my MacOS machines, for example. But OSX, out of the box, won't write to NTFS (it can read and mount the file system, because Microsoft has released that part of the specification). Non-UNIX/Linux OS's also have the same issue.

However those options that can write to NTFS on non-Microsoft OS's are reverse-engineered solutions, and Microsoft has in the past made minor changes to NTFS that break, for a time, these options.

The take home point is NTFS won't be a universal file system now or in the foreseeable future, which is what ordinary consumers need.
 
Last edited:
Originally Posted By: Johnny2Bad
Newer Flash drives have load-managing software built in (on a hidden partition). Essentially the load management insures files are written to a new area of the drive each time because flash memory has a limited number of write cycles before it fails. So the software insures the entire drive is written to, before it goes back and starts re-writing on an area previously used.

[...]
As a result, the flash drives last longer but that hidden partition eats at capacity.

Thanks for this explanation, by the way. Makes sense, and it sounds like a fair trade off, if it does extend useful life in a meaningful way. I just wish SanDisk was more open about it and made it clear what the actual usable storage space was.
 
Originally Posted By: Johnny2Bad
It should maybe be noted that most (possibly all) Digital Cameras also use FAT32.

Yup. The 4GB file size limit is not an issue for images. It does become an issue for video recording, especially with the newest 4K format. Alas, if you bounce against the file size limit, the camera will just automatically split it into separate files and you can stitch them together later, so technically nothing gets lost.
 
Status
Not open for further replies.
Back
Top