SD & SDHC maintenance

I emailed SanDisk earlier today about refreshing data on a SD or SDHC card and their response was:


... we recommend that you format the card once in a while. Please be aware that formatting is a normal and necessary method of drive maintenance and repair, and simply NOT formatting periodically can cause a drive to slip into failure due to the backup, and clutter of residual data.

After formatting, you can transfer the files back to the card. Doing this will refresh the card's system.


So, will that cause the directory/folder numbering to be reset on each card?

And how often is once in a while? Monthly? Yearly? after filling te card 10/200/500/1000 times?

Atleast do it not to often, it will rewrite your whole card and since they "only" last several thousands of rewrites. I will do it monthly or so.

You can see it as renewing your bookshelf, by throwing away every book and your old bookshelf and place a fresh new one.

I format the card EVERY time I put it back in the camera!

Am I doing it too often,

ali

I spend my working days writing firmware for data storage into NAND Flash devices. The endurance cycle of NAND flash (which is what SD/SDHC cards are) are typically 100,000 erase/write cycles - but that's worst case conditions. Generally the firmware adds EC (error correction) to that, so that even when single bits fail they can be mathematically reconstituted.

Data retention is spec'd at 10 years (ie it'll hold the data for a minimum of ten years without power etc).


Personally I format in-camera after I've copied the data to 3 hard drives. (But I actually cycle three 4Gb SDHC Extreme III cards, and only format when I insert into the camera to actually use the card.)

Matt

Like Ali I format every time I download the photos on to my computer(and after backing up - only once! - do I need another hard drive??). I do this with the card in the camera - presumably it doesn't matter whether you use a card reader or download via the camera?

John

Another who re-formats every time the card goes back into the camera, do know that you can delete but did not think it mattered - does it - am I hastening my cards to the grave. Never had one fail on me yet but there is always a first time and it will always be the worse possible moment.

Deleting is not good housekeeping, because you leave folders and untidy bits on the card. The capacity of the card will slowly reduce and eventually it could fail.

Formatting gives everything a spring clean and sets the card up for the camera with maximum efficiency.

I have had a second response from SanDisk.

Generally they suggest that if cards are being used for long term storage then they should be "checked" every few months and not subjected to extreme changes in temperature.

It is also said that formatting is essential to clean out old directory entries and dross left by deleting files. This can be done every few months too and it not necessary each time the card is inserted into the camera.

I am a little surprised at these answers. I have had one card in my K20 since I bought it last year. My shutter count is 3543. I formatted the card when I put it in and had not done so since.

When I connect to my PC, I usually cut the photos from the camera and paste them onto my hd. I was convinced that the capacity was 104 pictures best jpeg + raw and I still have that. To prove it to myself, I formatted the card and sure enough, 104.

Normally, I would expect deleting a file to remove it's entry from the file address table and any sectors allocated to it would then become available for writing.

Am I missing something?

I don't believe it's normally necessary to reformat the card, but doing so with the camera is easy and actually quicker than deleting files in the normal way.

I find the info from Sandisk somewhat strange.
Deleting or formatting does the same because a format only erases the FAT this is why you can use "undelete" software on memory cards if you haven't written anything new to the card. The data is still on de card but the reference where the data is on de card is deleted.

You've got it right Oggy. The file system is the same as a DOS hard drive and we don't reformat them. They do have a bit of junk in the FAT's but that just gets overwritten as needed. 3543 files being written and deleted is nothing for a FAT 32 drive.

The format the camera does is probably just a Quick format anyway. If you want to do a FULL format properly with a computer you need the Panasonic formating software to comply with the SD spec. The normal windows format does not comply.

I never reformat my cards I always delete the files from my computer when I've copied them over.

I've used Flash cards for years in Pocket PC's, Cameras, MP3 players, DAB Radios etc. and only ever had one problem with a Compact Flash card when the capacity dropped right down. Luckily I had a parallel port reader and could access the card through DOS, so I used Fdisk to delete the partition and create a new one... got the full capcity back after a FULL reformat.

shim

When you delete an image you don't delete it but give the sectors free to be rewriten, atleast that my understanding about it.

That's right as far as I know. You remove it's entry from the File Allocation Table. This file holds information on which sectors are used and which are free. Basic recovery programs work by actually reading all sectors, rather than looking at the FAT. This is why if you if you accidentally delete something, you should immediately stop using that media until you can you can unleash recovery software on it. The information is still there until it is overwritten.

Now that 4 GB ultra II SDHC cards are dirt cheap (EUR 12,50 last time I looked at schiphol)....my cards go through fewer write delete cycles... It's not like when 1GB cards were 100 pounds plus:shockremember those days:wink....

I routinely format my cards once I've written my photos onto my PC and backed them up...at least it saves me from trying to recall whether I've downloaded any pictures when I am out on location. Just part of my workflow...