Minimum SD card size?
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I guess this is the right place to ask this? What is the minimum SD card size, in standalone mode? It looks like the FAT32 partition is currently 250MB? The RPi partition is 3.32GB, so I guess 4GB for SBC mode.
As SBC mode is still broken for our needs I am having to make this reliable in standalone mode. That means using an SLC uSD card with power fail protection. It is £100 for a 4GB one. It is £34 for a 1GB one. Hence my query. Cheers.
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@theolodian it relies on how big your gcode files are really.
if you print something and then are happy to delete the files then 1gb would be fine.
if you want to keep loads of past files, then larger is better -
@jay_s_uk Thanks. This changes my whole approach to the API as well, so I will have to get up to speed on that in standalone mode.
Here is the uSD card in case anyone else wants to know. https://uk.rs-online.com/web/p/micro-sd-cards/1874667
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@theolodian you obviously have some quite significant requirements, but as a data point I had a (clone) duet wifi which came with a 128Mb sd card which ran fine. I could only have one or two gcode files on it at a time, but it ran fine. I've now swapped it to 4GB and can be lazy and never have to delete a file
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@theolodian said in Minimum SD card size?:
That means using an SLC uSD card with power fail protection.
I do not see any advantage in using such a card.
If power fails in the middle of a file write, as data in the SD filesystem is being updated, something will be corrupt no matter what card you use. The data in Duet RAM buffers is lost and no card can magically recover data never sent to it.
Also, internal power failure protection has been a feature of the SD card standards for at least a decade & possibly rather more.
I'd think you are better off with normal but good quality SDs such as Sandisk Extreme Pro, and take image copies of the configured machines so you can recreate the working cards in a couple of minutes if it ever needed.
I use those, the 64GB ones are on offer - only £14 at Amazon, checking just now; about the same as the 32GB usually are.
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@rjenkinsgb My concern is when the internal management of the SD card moves data around to manage wear. If the power goes off then it corrupts the whole partition.
These are to be in machines in factories that I do not have ready access to. Robustness is paramount. We were trying to achieve this with a RPi running off of an SSD...
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@theolodian
The simple thing is to ask Sandisk tech support: -
SLC cards work great so far. Obviously it will probably be a long time before I can comment on how robust they might be, however it seems like cheap insurance if you want less worries about SD card failures.
I just used a Windows PC to copy the files from the visible (FAT32) partition of the old card to the already formatted new card.
