RE: Fio verify crc32 fault

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After you update to the latest fio, also consider adding serialize_overlap=1 as a parameter (HOWTO has background there).  With large random writes, there is some probability (increasing with smaller device size and increasing with higher QD) that two inflight IO's conflict in range/time.  Suppose the first write is acknowledged by the device while the second conflicting write is already sent.  By the time fio reads the first command, the second write will change the data, causing verification errors.

Regards,
Jeff

-----Original Message-----
From: Sitsofe Wheeler <sitsofe@xxxxxxxxx> 
Sent: Friday, December 4, 2020 6:42 AM
To: Peter Sabaini <peter@xxxxxxxxxx>
Cc: fio@xxxxxxxxxxxxxxx
Subject: Re: Fio verify crc32 fault

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Hi,

On Thu, 3 Dec 2020 at 17:27, Peter Sabaini <peter@xxxxxxxxxx> wrote:
>
> Hey,
>
> I've got a fio verify run on an NVMe that gives me a crc32 verification fault, however it's not reproducible -- when rerunning on the same NVMe it comes back fine.
>
> Also I'm getting a funny "error=Invalid or incomplete multibyte or wide character" error reported, see below.
>
> Any hints for this?
>
> Many thanks,
> peter.
>
> Test output
>
> Running command: sudo -n fio --randrepeat=1 --ioengine=libaio 
> --direct=1 --gtod_reduce=1 --name=fio_test_verify --bs=4M --iodepth=64 
> --size=95% --verify=crc32c-intel --runtime=7200s 
> --filename=/dev/nvme0n1 --readwrite=randwrite
>
> fio_test_verify: (g=0): rw=randwrite, bs=4M-4M/4M-4M/4M-4M, 
> ioengine=libaio, iodepth=64
> fio-2.2.10

^^^ Your fio is VERY old... Does the same thing happen with a recent fio (see https://github.com/axboe/fio/releases for what we're up to)?

--
Sitsofe | http://sucs.org/~sits/




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