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Date:      Wed, 20 Jul 2022 21:30:06 +0200 (CEST)
From:      Wojciech Puchar <wojtek@puchar.net>
To:        Wei Hu <weh@microsoft.com>
Cc:        "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, "freebsd-hackers@FreeBSD.org" <freebsd-hackers@freebsd.org>, Li-Wen Hsu <lwhsu@freebsd.org>, Souradeep Chakrabarti <schakrabarti@microsoft.com>, "andrew@FreeBSD.org" <andrew@freebsd.org>
Subject:   Re: UFS checksum error during arm64 VM installation 
Message-ID:  <c717b236-a8ec-2193-b197-47a02624e21e@puchar.net>
In-Reply-To: <SI2P153MB04415A8C3BBB4E1FFD2237DABB8F9@SI2P153MB0441.APCP153.PROD.OUTLOOK.COM>
References:  <SI2P153MB04415A8C3BBB4E1FFD2237DABB8F9@SI2P153MB0441.APCP153.PROD.OUTLOOK.COM>

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hard to say. I've never in my life seen such an error, using FreeBSD for 
about 15 years, lots of different computers.

Anyway i never used FreeBSD as guest on any VM, and i don't use Windows 
nor it's VM host software.

May be a bug in Hyper-V that improperly emulates SCSI controller (i think 
it's emulating SCSI because your device is /dev/da*) - which result in 
error only on some kind of loads. ZFS and UFS works completely different. 
For example UFS is far more probable to do parallel writes to different 
locations in the same time.

In the other hand it may be FreeBSD bug if Hyper-V emulated SCSI conform 
to standards but behave different than real SCSI controller and disk.

As you are from microsoft you certainly could debug hyper-V to check if 
all reads and writes perform properly - i.e. writes data that it should 
write from guest memory, reads what it should and place in guest memory 
properly.

I sugges to force fsck on this partition to check if it shows this 
checksum error or not. fsck doesn't do parallel reads

If not - it's read handling problem.

If yes - it may be both, but most probably write handling problems.



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