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Wear Leveling - How many time can overwrite?

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(@wotsits)
Posts: 253
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Topic starter
 

I know there could likely be some sarcastic replies to this but anyway, let me just say I know it's not an exact science and I'm just looking for some rough idea.

This is for people who have some knowledge/experience of how wear leveling affects the life of SSDs.

If say you have a 100GB thumb drive, how many times can you fill it up, wipe it and then fill it up again?

I know there are variables as always and if it's not possible to give a close guess, are we talking 10s of times… 100s… 1000s?

 
Posted : 29/04/2016 4:18 pm
(@sam305754)
Posts: 44
Eminent Member
 

Hi,

Not a specialist on NAND tehcnology but my guess is
Single Level Cell supports 100 000 PE cycles per block.
MLC has lower endurance 10 000 PE cycle per block.
eMLC supports 30 000 PE per block.

Regards

 
Posted : 29/04/2016 4:48 pm
(@wotsits)
Posts: 253
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Topic starter
 

So are we certainly talking 10000s of wipe and overwrites?

The only reason I ask is because I use a simple thumb drive to back up my computer, once a week I simply delete the thumb drive then copy all the files over again.

If I understand you correctly, then at this rate we will be driving around in hover ships before the thumb drive runs out.

 
Posted : 29/04/2016 5:39 pm
jaclaz
(@jaclaz)
Posts: 5133
Illustrious Member
 

Just for the record a "simple" thumb drive may (or may not) use a SSD internally and it may have (or it may have not) a wear leveling mechanism (though most have).
Some "high speed" USB 3.x thumb drive consist actually of a USB to SATA bridge and of a "normal" (miniature) SATA SSD, but they are AFAIK the exception.

Anyway, talking of a wipe/write cycle per week, hover ships will be a thing of the past when your stick will be affected by wear. wink

jaclaz

 
Posted : 30/04/2016 11:06 pm
(@athulin)
Posts: 1156
Noble Member
 

This is for people who have some knowledge/experience of how wear leveling affects the life of SSDs.

If say you have a 100GB thumb drive, how many times can you fill it up, wipe it and then fill it up again?

That question has been answered (in a way) by Tech Report – see http//techreport.com/review/27909/the-ssd-endurance-experiment-theyre-all-dead

They did just as you describe took a number of commercial SSD disks, and wrote to them until they failed. Some disks died around 1 petabyte of written data, some other kept going after 2 petabyte.

I know there are variables as always and if it's not possible to give a close guess, are we talking 10s of times… 100s… 1000s?

The arithmetic I leave to you.

Remember to take the wipe you include into account. From the point of the disk, it is likely to be just another write cycle.

And also factor in behaviour at point-of-death some SSDs may go into read-only mode to allow you to salvage what is already on the disks.

Also … these are not thumb drives. Thumb drives are likely to perform worse. You may want to repeat the test described – hunt down that 'Anvil Storage Utility' test software that was used, and test your own choice of storage equipment.

Personally, I would do just as I once did with magnetic tape storage used for important data such as backup I'd cap usage. Once an important storage medium (magnetic tape or thumb drive) had either been used more than N times, or it had grown older than M years, I'd replace it. (Though the age factor is probably more important for magnetic tape than for SSD drives.)

So far, no important thumb drive has lasted that long – I've typically bought bigger and faster drives long before, and the old drives have become degraded to convenience drives.

 
Posted : 01/05/2016 10:50 am
jaclaz
(@jaclaz)
Posts: 5133
Illustrious Member
 

So far, no important thumb drive has lasted that long – I've typically bought bigger and faster drives long before, and the old drives have become degraded to convenience drives.

… and I would add the "tiny size factor" 😯 (that makes it very likely that you simply loose the thumb drive) and the possibility that you mistake the thumbdrive with a similar one.

As a side note, there was a nice product by PNY that was aimed to store data on thumbdrives (as a replacement for floppies) where the thumbdrive had a label and a nice protection mechanism for the connector, but has been discontinued and I don't think there is a similar product available
https://www.amazon.co.uk/PNY-Attache-Storage-4GB-Drive/dp/B003UAKAJ8?ie=UTF8&*Version*=1&*entries*=0
http//www.memory-express.co.uk/p/613472

jaclaz

 
Posted : 01/05/2016 5:22 pm
(@trewmte)
Posts: 1877
Noble Member
 

Wotsits, here is one from the many documents in the Institute for Digital Forensics (IDF) archive. If you need anymore let me know.

Hope it helps.

The Fundamental Limit of Flash Random Write Performance Understanding, Analysis and Performance Modelling - https://www.dropbox.com/s/8a66duhnc2b5w09/hot_cold.pdf?dl=0

 
Posted : 02/05/2016 1:06 am
(@mscotgrove)
Posts: 938
Prominent Member
 

Please backup onto more than a single device.

With multiple thumb drives, you could always ensure that one of the backups is stored in a different location. Your present situation could mean that a power surge might kill the PC just after you have cleared down your backup thumb drive.

No single storage device is totally reliable, and so assume it could fail at any time. Automatic online systems work well, subject to rules and regs on data protection etc.

 
Posted : 02/05/2016 7:38 pm
(@paul206)
Posts: 70
Trusted Member
 

Most of the time a USB flash drive will not have wear leveling. You will usually only see it on an SSD. I would suggest an encrypted USB hard drive or several write protected flash drives. Or get a USB hard drive docking station and just pop in a standard 5 1/4 inch drive and then put it away in the evidence locker. You could also spend some bucks for a NAS.

 
Posted : 06/05/2016 7:59 pm
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