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From: Tetsuhiro Kohada <kohada.t2@gmail.com>
To: Namjae Jeon <namjae.jeon@samsung.com>
Cc: kohada.tetsuhiro@dc.mitsubishielectric.co.jp,
	mori.takahiro@ab.mitsubishielectric.co.jp,
	motai.hirotaka@aj.mitsubishielectric.co.jp,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	'Sungjong Seo' <sj1557.seo@samsung.com>
Subject: Re: [PATCH v3] exfat: remove EXFAT_SB_DIRTY flag
Date: Tue, 18 Aug 2020 10:20:14 +0900	[thread overview]
Message-ID: <6a6a85b7-5cff-7bb0-98e5-4d7ece86bb19@gmail.com> (raw)
In-Reply-To: <001501d67126$b3976df0$1ac649d0$@samsung.com>

Thank you for your reply.

>>> Most of the NAND flash devices and HDDs have wear leveling and bad sector replacement algorithms
>> applied.
>>> So I think that the life of the boot sector will not be exhausted first.
>>
>> I'm not too worried about the life of the boot-sector.
>> I'm worried about write failures caused by external factors.
>> (power failure/system down/vibration/etc. during writing) They rarely occur on SD cards, but occur on
>> many HDDs, some SSDs and USB storages by 0.1% or more.
> Hard disk and SSD do not guarantee atomic write of a sector unit?

In the case of SD, the sector-data will be either new or old when unexpected write interruption occurs.
Almost HDD, the sector-data will be either new, old, or unreadable.
And, some SSD products have similar problem.

>> Especially with AFT-HDD, not only boot-sector but also the following multiple sectors become
>> unreadable.
> Other file systems will also be unstable on a such HW.

A well-designed FileSystems never rewrite critical regions.

>> It is not possible to completely solve this problem, as long as writing to the boot-sector.
>> (I think it's a exFAT's specification defect) The only effective way to reduce this problem is to
>> reduce writes to the boot-sector.
> exFAT's specification defect... Well..
> Even though the boot sector is corrupted, It can be recovered using the backup boot sector
> through fsck.

Exactly.
However, in order to execute fsck, it is necessary to recognize the partition/volume with broken boot-sector as exfat.
Can linux(or fsck) correctly recognize the FileSystem even if the boot-sector cannot be read?
(I don't yet know how linux recognizes FileSystem)
In fact, a certain system recognize it as 'Unknown format'.
Nowadays, exfat is often used for removable storage.
This problem is not only for linux.

BR
---
etsuhiro Kohada <kohada.t2@gmail.com>

  reply	other threads:[~2020-08-18  1:20 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200616021816epcas1p44b0833f14bbad0e25cc0efb27fb2ebd3@epcas1p4.samsung.com>
2020-06-16  2:18 ` Tetsuhiro Kohada
2020-06-16 23:55   ` Namjae Jeon
2020-06-17  7:20   ` Sungjong Seo
2020-06-17  8:41     ` Namjae Jeon
2020-06-18  8:36     ` Tetsuhiro Kohada
2020-06-18 13:11       ` Sungjong Seo
2020-06-19  4:22         ` Tetsuhiro Kohada
2020-07-10  7:36         ` Tetsuhiro Kohada
2020-08-08 17:47           ` Sungjong Seo
2020-08-12  9:19             ` Tetsuhiro Kohada
2020-08-13  4:03               ` Namjae Jeon
2020-08-18  1:20                 ` Tetsuhiro Kohada [this message]
2020-06-16  6:16 Markus Elfring
2020-06-16 14:45 ` Matthew Wilcox

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