File IO write flush time span

File IO write flush time span

[JH]

Hi,

If I write a file to a UBIFS volume, how long the mtd will write it
from cache to physical NAND? I try to understand in what time span
those IO writing in cache will be lost if the power is turned off
(lost power).

Thank you.

Kind regards,

- jh

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Re: File IO write flush time span

[Richard Weinberger]

On Tue, Feb 25, 2020 at 6:58 AM JH <jupiter.hce@gmail.com> wrote:
>
> Hi,
>
> If I write a file to a UBIFS volume, how long the mtd will write it
> from cache to physical NAND? I try to understand in what time span
> those IO writing in cache will be lost if the power is turned off
> (lost power).

What cache do you have in mind?
As soon ubiupdatevol terminates, the volume is in stable state.

-- 
Thanks,
//richard

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Re: File IO write flush time span

[JH]

Hi Richard,

On 2/25/20, Richard Weinberger <richard.weinberger@gmail.com> wrote:
> On Tue, Feb 25, 2020 at 6:58 AM JH <jupiter.hce@gmail.com> wrote:
>>
>> Hi,
>>
>> If I write a file to a UBIFS volume, how long the mtd will write it
>> from cache to physical NAND? I try to understand in what time span
>> those IO writing in cache will be lost if the power is turned off
>> (lost power).
>
> What cache do you have in mind?
> As soon ubiupdatevol terminates, the volume is in stable state.

I was actually talking about applications write files to a UBIFS
volume mounted as RW in Linux, let's say if I write a file by vi, will
it immediately flush to the NAND or will it stay in cache until some
algorithm in MTD to erase NAND pages and flush the cache to NAND page
based on size of output or time, is it correct?

Thank you.

Kind regards,

- jh

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: File IO write flush time span

[Richard Weinberger]

On Tue, Feb 25, 2020 at 9:45 AM JH <jupiter.hce@gmail.com> wrote:
> I was actually talking about applications write files to a UBIFS
> volume mounted as RW in Linux, let's say if I write a file by vi, will
> it immediately flush to the NAND or will it stay in cache until some
> algorithm in MTD to erase NAND pages and flush the cache to NAND page
> based on size of output or time, is it correct?

UBIFS is a filesystem and follows the rules of the vfs and pagecache.
But it is less forgiving than ext3/4. To make sure data hits the NAND you
need to properly use fsync/fdatasync().

-- 
Thanks,
//richard

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