Jump to content
Sign in to follow this  
vohne

256GB SD on the T

Recommended Posts

Pico,

 

It is funny, I removed the bit that I wrote about block remapping when I was talking about disks because I didn't think it was ncessary. I forgot about the nearly full problem with Flash. Otherwise I would have included it. Thanks for covering it BTW it isn't just SDHC it is anything using Flash. I'm kind of surprised at the 30% number but I haven't kept up on the process technology.

 

One thing that makes it considerably better on flash based SSDs is a well designed file system will tell the disk that it is no longer using those blocks when a file is deleted. This allows the block remapping algorithithms in the Flash wear leveler to perform better. The problem is FAT is not a well designed file system. Given how critical it is, I wouldn't be surprised if SD cards kind of pay attention to when you rewrite the first few blocks of the file system. Then they know that the card is being reformatted and they know that they can drop all their previous mappings between blocks and cells.

 

This is all hidden away in the firmware in the SD card below where I work and is proprietary trade secrets. However, sort of extending on what Pico said, and based upon what I know about how these things work, I've always suspected that erasing files might not be quite as useful as formatting the card. So maybe reformat them from time to time. Especially after you have nearly filled them up.

 

Some other tips:

1) In general don't expect a SD card to last forever.  THEY ARE NOT a backup device. The data on them will spontaneously decay.

2) buy a bigger one and use less of it if you can

3) these things are amazingly cheap for the capacity. Remember how thin their margins are when you buy them and don't be too upset when you have a problem with quality. These guys are working miracles of physics and software to make a few pennies.

Share this post


Link to post
Share on other sites

I meant the difference at the partition table / file system level. I kind of feel like you are writing responses to a different set of statements than what I posted.

 

Originally I was suggesting that maybe the larger card could be partitioned. pico implied that SD cards were so different that partitioning was fundamentally different from my understanding.

 

But as I said, I tried making multiple partitions on a smaller SD card and the T just uses the first partition like I originally assumed.

Edited by julian m

Share this post


Link to post
Share on other sites

fwiw, SDXC cards over 32 GB are usually ExFAT anyway, which was designed with flash memory and larger storage space in mind.

Share this post


Link to post
Share on other sites

fwiw, SDXC cards over 32 GB are usually ExFAT anyway, which was designed with flash memory and larger storage space in mind.

Right ExFAT. 

 

Designed for flash. Err - um - yeah - kind of, sort of. Let's just say that it looks like Microsoft's spin meisters were involved. If you could format a disk this big FAT would suck. Since you can format a disk as big as a modern disk with ExFAT someone might be tempted to do so and it would really really suck. However with the random access capabilities of Flash, it won't be too bad. So rather than saying, "FAT and ExFAT are primitive antique file systems whose main purpose is compatibility and whose primary feature is very simple implementation" they make it sound positive and say "designed for Flash" where its weaknesses are not quite so evident.

 

The feature that really helps out Flash is known as trim or discard. Up to ExFAT at least version 1.6, I have not been able to find any evidence for support for trim in the ExFAT. Evidently the current version is 1.7 but I can't find any documentation about it having it either. A particular implementation not tied to Microsoft's might have it though. But if Microsoft doesn't have it then it, then it is unlikely that most cards will implement the trim command. Even if they do implement the trim command, if Microsoft doesn't use it, then it will likely be buggy. I won't mention the vendors but when we started enabling trim support for SSDs for our FSs, we had all sorts of problems with vendors firmware crashing and resetting or locking up. We had to disable it by default and then allow people to explicitly turn it back on.

Share this post


Link to post
Share on other sites

Originally I was suggesting that maybe the larger card could be partitioned. pico implied that SD cards were so different that partitioning was fundamentally different from my understanding.

 

But as I said, I tried making multiple partitions on a smaller SD card and the T just uses the first partition like I originally assumed.

 

Thank you for testing that in real life.  It would be terrific if we could use other partitions.

Share this post


Link to post
Share on other sites

Right ExFAT. 

 

Designed for flash. Err - um - yeah - kind of, sort of. Let's just say that it looks like Microsoft's spin meisters were involved. If you could format a disk this big FAT would suck. Since you can format a disk as big as a modern disk with ExFAT someone might be tempted to do so and it would really really suck. However with the random access capabilities of Flash, it won't be too bad. So rather than saying, "FAT and ExFAT are primitive antique file systems whose main purpose is compatibility and whose primary feature is very simple implementation" they make it sound positive and say "designed for Flash" where its weaknesses are not quite so evident.

 

The feature that really helps out Flash is known as trim or discard. Up to ExFAT at least version 1.6, I have not been able to find any evidence for support for trim in the ExFAT. Evidently the current version is 1.7 but I can't find any documentation about it having it either. A particular implementation not tied to Microsoft's might have it though. But if Microsoft doesn't have it then it, then it is unlikely that most cards will implement the trim command. Even if they do implement the trim command, if Microsoft doesn't use it, then it will likely be buggy. I won't mention the vendors but when we started enabling trim support for SSDs for our FSs, we had all sorts of problems with vendors firmware crashing and resetting or locking up. We had to disable it by default and then allow people to explicitly turn it back on.

 

Sure, but you're comparing ExFAT to real filesystems!

I'll take ExFAT over FAT32 any day.

 

And yes, I've worked at a place where my coworkers had first-hand experience with exactly the trim issues you describe. Oh disk vendors. Writing firmware.

Share this post


Link to post
Share on other sites

 

Sure, but you're comparing ExFAT to real filesystems!

I'll take ExFAT over FAT32 any day.

 

 

Any thoughts about a strict SD, SSD format?

.

Share this post


Link to post
Share on other sites

It seems like a 128GB card seem to work. This is double the listed 64GB in the manual.

 

I have a 32GB SanDisk extreme pro 95MB/s U1 class 10 card and when freshly formatted it has 979 shots

I tossed in a 128GB Sony 94MB/s U3 class 10 card which is one of the ones that didn't work well with firmware 1.3. There were frequent "Lens Errors" which is why I switched to the 32GB SanDisk. The 128GB Sony is reporting 3906 shots available which is about 4x as many.

 

Before I leave for my trip, I'll verify that 1.31 will work with the new card. It worked fine with firmware 1.2. I do expect that there may be some performance issues with thousands of shots on the card but I haven't gone there yet.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...