life time on USB live cd or TCL use

[Daniel]

A new topic for tife time for TCL on USB (or ubuntu live cd).

Ours machines are actually on ubuntu 8.04 live cd, installed on USB key.
Our application is on ro disks, and user configuration or counters are written synchronized on two rw partitions.

After 1.5 years, there is some bad files on live cd partition (where kernel, ... and squashfs is written on fat32 filesystem).

The only 'actions' are formating counter partition when there is file access error.



We will use TCL on one actual machine (runs ok) and probably futurs products.
(i've got problem with starting X on an other machine).

With TCL, same usage would be done.


I suppose formating partition may acces to MBR and may contribute recduting usb life time.

Who have any information or experiment confirming (or not i expect) what i can suppose ?


Thanks,
Daniel.

[gerald_clark]

Your question is not clear.
Just reading the MBR will not reduce the life of the drive.

[Daniel]

I know about "reading" 

I said :

I suppose formating partition may acces to MBR and may contribute reducting usb life time.

D.

[Rich]

Hi Daniel
The main thing that limits the life is the number of times you write to it. Formatting counts as a write.
The easiest way to extend the life is to write your data to a file in RAM and update the device only
when you shut down. If you insist on constantly writing to the device you will have to implement some
form of wear leveling it you want to extend it's life.

[Daniel]

Thanks Rich!

I precise the partition witch 'loose files' is not the formated partition!

The question is : formating a device partition may reduce MBR life time, or not ? (disk in extended partition, or not).

Wear leveling is implemented in usb devices. It runs ok if there is umpartioned size (space remaining to be used if necessary).

D.

[gerald_clark]

Wear leveling is built-in for USB flash drives.
I still don't see what accessing the MBR has to do with anything.

[Rich]

Hi Daniel
Most likely formating will update the partition table in the MBR and effect it's life. How often are
you formatting and why?

[Guy]

The mbr is automatically created when the first partition is created.

If you delete the partition, and create a new one, the mbr will be written to.

If you just format an existing partition, the mbr is not written to.

Writing to the mbr should not affect the life of the usb drive any more than writing to any other part of the drive.


USB drives can normally be written to thousands of times before they fail.

Formatting is writing to it once. You should be able to write to it thousands more times.


To maximize the life of a usb drive:

Use the ext2 filesystem, as it is not a journalling filesystem. This reduces the amount of writing.

Use backup in Tiny Core, not persistent home and opt. When you save something, it will be saved to ram. The usb drive will only be written to when you turn the computer off. Unless you backup sooner.

[Daniel]

Thanks to everybody!

I've got informations about USB and wear leveling:

Commercial USB key are using 'BAD flash'!
Manufacturers may plug 8Gb in order to obtain a 4Gb usb key correct size (destructed sectors).

Wear leveling is flash managed over usb 'official' size.
This size is constructor dependant (choice) x mb to 100mb ?

More :
No guaraty is done for life time!

In fact, i can have some bad usb key witch have the problem.


That's why i'm looking for USB DOM (industrial usb). (more write number, write speed increased ...)


But i have an other problem:
When i write many data (200Mb program installation), i've got crc errors when checking after copy, (detected) or bad written file, even if crc tells no error. (very more on industrial than commercial usb key)

It is explained with the USB RAM buffer (bigger than the commercial USB because of speed).
--> When the usb key said "write finished ok", the RAM buffer is not empty, and writing not terminated.
Even if sync or umount is done : usb traffic is finished, not usb internal write.


Then, i'm looking to know how i can know when that's finished.
One possibility is to "eject" the usb device.
Is it possible on a disk partition ? (same result?)

But i don't remove usb key : is it possible to "insert a partition" ?

or ?

Thanks
Daniel.

[tinypoodle]

Logically there should be less of a concern for MBR in comparison to all other sectors, as write cycles lifetime is measured by the thousands, and hardly anyone would update a MBR thousands of times...