ATA -- erratic behaviour when removing disk
Carlos A. M. dos Santos
unixmania at gmail.com
Sat Feb 16 23:08:40 UTC 2008
On Feb 16, 2008 7:07 PM, Jeremy Chadwick <koitsu at freebsd.org> wrote:
> Is anyone aware of the situation where FreeBSD behaves erratically when
> a disk is physically removed without "atacontrol detach ataX" being run
> prior to removal (at least on RELENG_7)?
Yes, I have seen this since 4.5, IIRC.
> Below are my notes from said situation.
>
> I can provide remote access to this machine (serial-level) to whoever
> wants to hack on it. I can be available for disk removal/insertion as
> well; just ask.
>
> Also FWIW: I also tested all this for comparison on Ubuntu Linux earlier
> this morning. I was able to yank the disk in the middle of an I/O
> operation, resulting in an immediate I/O error from dd. I took no
> precautions prior to yanking the disk. Upon reinsertion, the system
> found the disk and I could continue I/O operations on it as if it had
> never been removed. Only reason I'm pointing this out is that it
> confirms the issue isn't hardware or with vendor implementation, but
> rather specific to the OS.
Congratulations to the Linux folks. Or not, since this looks like a
very risky behavior. Who warrants you that the *same* disk was plugged
back? Blindly continuing to write could easily corrupt the contents of
the second drive.
> --
> | Jeremy Chadwick jdc at parodius.com |
> | Parodius Networking http://www.parodius.com/ |
> | UNIX Systems Administrator Mountain View, CA, USA |
> | Making life hard for others since 1977. PGP: 4BD6C0CB |
>
> Hardware:
> Supermicro SuperServer 5015M-T+B
> Intel ICH7
> AHCI enabled (version 01.10), BIOS-based RAID disabled
> ad4: 190782MB <WDC WD2000JD-00HBB0 08.02D08> at ata2-master SATA150
> ad6: 190782MB <WDC WD2000JD-00HBB0 08.02D08> at ata3-master SATA150
>
> OS installed on /dev/ad4 and OS was booted with verbose logging enabled:
>
> FreeBSD 7.0-RC2 FreeBSD 7.0-RC2 #0: Fri Feb 8 00:09:57 UTC 2008 root at logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
[lengthy contents purposefully removed in the reply message]
--
Carlos A. M. dos Santos
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