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Subject: Re: RAID1 disk upgrade method
To: Sean Greenslade <sean@seangreenslade.com>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>
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From: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>
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Date: Thu, 28 Jan 2016 14:37:59 -0500
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On 2016-01-28 13:47, Sean Greenslade wrote:
> On Thu, Jan 28, 2016 at 09:18:06AM -0700, Chris Murphy wrote:
>> Those read errors are a persistent counter. Use 'btrfs dev stat' to
>> see them for each device, and use -z to clear. I think this is in
>> DEV_ITEM, and it should be dev.uuid based, so the counter ought to be
>> with this specific device, not merely "sda1". So ... I'd look in the
>> journal for the time during the replace and see where those read
>> errors might have come from if this is supposed to be a new drive and
>> you're not expecting read errors already.
>>
>> Like I mentioned in my first reply to this thread, sct erc... it's
>> very important to get these settings right.
>
> I don't see anything that indicates read errors in my journal or dmesg,
> though it's hard to tell given the rather scary-looking messages I get
> whenever I eject a drive:
>
> [Thu Jan 28 10:38:10 2016] ata6.00: exception Emask 0x10 SAct 0x8 SErr 0x280100 action 0x6 frozen
> [Thu Jan 28 10:38:10 2016] ata6.00: irq_stat 0x08000000, interface fatal error
> [Thu Jan 28 10:38:10 2016] ata6: SError: { UnrecovData 10B8B BadCRC }
> [Thu Jan 28 10:38:10 2016] ata6.00: failed command: READ FPDMA QUEUED
> [Thu Jan 28 10:38:10 2016] ata6.00: cmd 60/00:18:00:79:02/05:00:00:00:00/40 tag 3 ncq 655360 in
>                                      res 40/00:18:00:79:02/00:00:00:00:00/40 Emask 0x10 (ATA bus error)
> [Thu Jan 28 10:38:10 2016] ata6.00: status: { DRDY }
> [Thu Jan 28 10:38:10 2016] ata6: hard resetting link
> [Thu Jan 28 10:38:10 2016] ata6: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
>
If by eject you mean disconnect form the system, this is exactly the 
output I would expect if you haven't done something to tell the kernel 
the disk is disappearing.