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> microSD size
Adam Boardman
post Jan 16 2018, 05:17 AM
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On the subject of filing systems, has anyone figured out what are the best ones for wear levelling?

For anyone who dosn't know what it is then have a read of Wear_leveling

But basically our flash drives/cards are going to last for a much longer time if we have some part of the system doing that for us. It can happen in the flash controller hardware or in the drivers or in the filesystem. I'm hoping the internal drive is sorted by the controller/driver but have no evidence of this being the case, removable media on the other hand is unlikely to have this?

One additional thing to do is to set 'noatime' so that every read doesn't also cause a write: ReducingWrites
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speculatrix
post Jan 16 2018, 05:37 AM
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memory cards have an internal controller which does wear levelling, but I don't think they support TRIM?
on my DSLR, I occasionally (after copying off all the photos) do a secure erase on the card which esssentially factory resets the card so that the wear-levelling can work more effectively. You need the right kind of memory card reader and to use the official SD card formatter in the right mode for that: https://www.sdcard.org/downloads/formatter_4/

I don't know anything about the memory controller in the Gemini, whether it's simply flash connected directly to the CPU with the OS taking care of wear levelling, or if there's an intermediate controller. Hopefully the latter. If the former, you definitely want to be using F2FS with TRIM, and never put swap on the internal flash to avoid destroying part of it.

p.s. and a lot depends on whether its SLC flash or MLC etc, the former gives many more write/erase cycles.
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Varti
post Jan 16 2018, 06:20 AM
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I'll be also using F2FS on my SD card with no swap partition, as suggested by speculatrix. I already use that filesystem on my Sharp Zaurus and I never had any problem with it.

By the way, does anybody know what type of internal storage will be used on the Gemini? Will it be an M.2 SSD drive (https://en.wikipedia.org/wiki/M.2, and thus will it be possible to upgrade it?

Varti
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Alius
post Jan 16 2018, 06:58 AM
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I thought most phone-like devices (and some budget convertible x86 tablets) used eMMC, but I could be mistaken. Since Planet seems to be trying to leverage some existing turnkey hardware to focus on the uniqueness of the form-factor, I would be (pleasantly) surprised if they were able to put a true SSD in the Gemini
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speculatrix
post Jan 16 2018, 07:31 AM
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I'm pretty sure it will be eMMC. We have to hope they will have used an eMMC 5 module with high performance supporting HS400, to give good random I/O as well as sustained reads and writes.

I found this useful table:
https://www.datalight.com/solutions/technol...ison-by-version
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Grench
post Jan 16 2018, 12:33 PM
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Gemini flash thoughts...

M.2? No.
Removable SSD? No.
Soldered on eMMC module? Definitely.

On partitions and formats...
For this I'm a bit torn.

Android since V6 has used EXT4 for it's own partition on the eMMC. But...

Depending on how the OEM (Planet Computers) sets up Android, it may or may not be willing to read any partition format other than Fat32 (cards <= 32GB) and ExFat (cards > 32GB).

There ARE Linux drivers for ExFat (Thank Google) utilizing FUSE. These can likely be made to work for Debian on the Gemini... maybe... They were able to make them work on the Pandora (Another ARM Linux computer).

I think Planet is planning to have us boot Linux from the microSD slot. Yet to be proven one way or the other. If this is the case, I'll probably put multiple partitions on my microSD card to use in the Gemini.

Something I'm still missing, and can't seem to find via searching... What is the definitive list of partition formats that Android 7 can support?


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speculatrix
post Jan 17 2018, 05:43 AM
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File system support comes down to the configuration used when the kernel was built.
Planet should release the kernel sources under the GPL and so it should be possible to replace the kernel or add modules to it restrospectively. And this is where the shadow of Mediatek looms, since devices based on Mediatek rarely get the full kernel sources released, and may require closed source binary blobs which make it hard or impossible to upgrade to a newer kernel.
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depscribe
post Jan 17 2018, 10:02 AM
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QUOTE(Adam Boardman @ Jan 16 2018, 05:17 AM) *
One additional thing to do is to set 'noatime' so that every read doesn't also cause a write: ReducingWrites


I just had a colorful hour or so, having applied the suggestions in this link and rebooting to a read-only filesystem such that I could not unedit /etc/fstab. Had to do a mount -o remount,rw /dev/sda2 / in order to be able to undo what I had done. Is this an ext4-only thing? Because in ext3 it makes for excitement but no joy. (Though I must confess that it reduced the number of writes to zero!)
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Adam Boardman
post Jan 17 2018, 10:10 AM
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RE: noatime causing zero writes (readonly filesystem)

I've only ever used it with ext4, but from googleing the idea it appears other people have used it with ext3? Could you post your from/to lines in-case it was some other change? (I've also updated the page to avoid others having the same problem, I'll test it on my Gemini when I get it and update the page - or anyone else can)
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depscribe
post Jan 17 2018, 10:37 AM
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QUOTE(Adam Boardman @ Jan 17 2018, 10:10 AM) *
RE: noatime causing zero writes (readonly filesystem)

I've only ever used it with ext4, but from googleing the idea it appears other people have used it with ext3? Could you post your from/to lines in-case it was some other change? (I've also updated the page to avoid others having the same problem, I'll test it on my Gemini when I get it and update the page - or anyone else can)


UUID=00c71d45-5bc2-40a7-b52f-cd73c82d294f / ext3 errors=remount-ro 0 1

became:

UUID=00c71d45-5bc2-40a7-b52f-cd73c82d294f / ext3 errors=remount-ro,data=writeback,noatime,nodiratime 0 1


UUID=f33fcb46-c800-4a83-acef-3952e6f813d7 /home ext3 defaults 0 2

became:

UUID=f33fcb46-c800-4a83-acef-3952e6f813d7 /home ext3 defaults,data=writeback,noatime,nodiratime 0 2

Do you suppose it's the data=writeback setting that blows things up?

(I also have an additional drive in the machine, formatted ext4, but it is data only and has no UUID line at all, though this shouldn't figure in booting at all.)

The write reduction fix is of interest because Linux tends toward a lot of unnecessary disk activity, and reducing it is a Real Good Thing.
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depscribe
post Jan 17 2018, 11:29 AM
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It appears definitely to be a problem with the data=writeback. Just tried without it and all is tickety-boo.
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Adam Boardman
post Jan 17 2018, 12:14 PM
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Excellent, I expect the access time bits have more of an impact than the writeback, so I'm glad they work for you.
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depscribe
post Jan 17 2018, 02:25 PM
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QUOTE(Adam Boardman @ Jan 17 2018, 12:14 PM) *
Excellent, I expect the access time bits have more of an impact than the writeback, so I'm glad they work for you.


There seems to be a noticeable performance increase as well. Thanks!
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depscribe
post Jan 17 2018, 07:26 PM
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QUOTE(Grench @ Jan 16 2018, 12:33 PM) *
I think Planet is planning to have us boot Linux from the microSD slot. Yet to be proven one way or the other. If this is the case, I'll probably put multiple partitions on my microSD card to use in the Gemini.


Not if this is accurate:

"Whichever model of Gemini PDA you choose, it already comes with a very healthy 64GB of on-board storage. Once you take into account the installed Android and Linux operating systems however, and then the space occupied by all your apps, and system and temporary files, that space will very quickly be significantly reduced. Many Gemini owners therefore will want to expand their storage with the addition of a MicroSD card."

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Grench
post Feb 2 2018, 10:46 AM
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QUOTE(depscribe @ Jan 17 2018, 09:26 PM) *
QUOTE(Grench @ Jan 16 2018, 12:33 PM) *
I think Planet is planning to have us boot Linux from the microSD slot. Yet to be proven one way or the other. If this is the case, I'll probably put multiple partitions on my microSD card to use in the Gemini.


Not if this is accurate:

"Whichever model of Gemini PDA you choose, it already comes with a very healthy 64GB of on-board storage. Once you take into account the installed Android and Linux operating systems however, and then the space occupied by all your apps, and system and temporary files, that space will very quickly be significantly reduced. Many Gemini owners therefore will want to expand their storage with the addition of a MicroSD card."


Considering the number of (likely unintentional) inaccuracies in those starter articles, it would not surprise me in the least if he's completely off in assumption land on those statements. No fault of his own, but the guy is a clearly writer trying to be a techie. I seriously doubt if he has anymore insights into the OS configurations on the Gemini than you or I do.

You will note through the articles that the author has never actually held a Gemini let alone looked at how the software is or isn't installed by default.
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