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Date:      Sat, 07 Sep 2013 21:39:14 +0300
From:      Alexander Motin <mav@FreeBSD.org>
To:        zhixiang yu <zxyu.core@gmail.com>
Cc:        soc-status@freebsd.org
Subject:   Re: Weekly report of the passed two weeks
Message-ID:  <522B72D2.7070906@FreeBSD.org>
In-Reply-To: <CADr9iNvmm-aX8SO3DQshzaNTS204%2Bep9gvGiOaymw4QMp=2-sg@mail.gmail.com>
References:  <CADr9iNvmm-aX8SO3DQshzaNTS204%2Bep9gvGiOaymw4QMp=2-sg@mail.gmail.com>

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Hi.

On 07.09.2013 19:26, zhixiang yu wrote:
> During the past two weeks, I successfully completed ata command
> emulation. The emulation passed some simple tests:
>
> 1. make partition
> 2. make label
> 3. format as ufs
> 4. copy and compare
> 5. umount and mount, then compare again

For stress test I would try to create ZFS pool on the device, disable 
ARC caching and run some heavy filesystem benchmark. ZFS controls disk 
subsystem sanity on every read and should report you any data 
inconsistency in `zpool status` output.

> You can try it yourself ;)
>
> The ATAPI commands' support is on-going. Maybe finished by next
> weekend. I won't need the same much time as ATA because I'm more
> familiar with read/write emulation.

While they are not recommended for use by AHCI specification, and may be 
not required to boot FreeBSD guest, I would still implement ATA PIO 
commands too because they are still mandatory for any ATA device. 
Fortunately since AHCI hides PIO transfer details it should be easy.

Also, looking on the code, I think that sending any unsupported command 
to the device now will cause command timeout, while it should return 
ABORT error status instead. And in general make sure that you 
implemented all commands support for which you announced in IDENTIFY 
command output.

Also I think it would be good to make FLUSHCACHE commands not only wait 
for write completion, but really call fsync() on the underlying file. 
That may be important for client filesystem consistency in case of host 
system crash.

-- 
Alexander Motin



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