Re: libata question

[Roger Oberholtzer <roger@opq.se>]

On Wed, 2006-08-02 at 16:20 +0900, Tejun Heo wrote:
> Roger Oberholtzer wrote:
> > On Wed, 2006-08-02 at 04:06 +0900, Tejun Heo wrote: 
> >> Roger Oberholtzer wrote:
> >>> On Wed, 2006-08-02 at 03:45 +0900, Tejun Heo wrote:
> >>>> Roger Oberholtzer wrote:
> >>>>> On Wed, 2006-08-02 at 00:33 +0900, Tejun Heo wrote:
> >>>>>> Roger Oberholtzer wrote:
> >>>>>>> Should hotplug work with Intel Corporation 82801GB/GR/GH (ICH7
> >>>>>>> Family) chipset? I am trying kernel 2.6.17.7
> >>>> Ah.. I should have spotted this earlier.  2.6.17.7 doesn't contain 
> >>>> updated EH and doesn't support any of new features including 
> >>>> hot/warmplug.  Please try 2.6.18-rc3.
> >>> OK. But I think there are issues with 2.6.18 generally. But I can try it
> >>> to see if this makes this better.
> >> If you're uncomfortable with -rcX, you can try libata-tj-stable patch. 
> >> It contains most of new stuff.
> >>
> >> http://home-tj.org/files/libata-tj-stable/libata-tj-2.6.17.4-20060710.tar.bz2
> > 
> > Thanks for that. But it had no noticeable difference.
> 
> Hmmm... That's weird. 'echo - - - > /sys/class/scsi_host/xxx.../scan' 
> didn't do the right thing?  Care to post dmesg?
> 
> > I looked in the bios on my system to see if I could set the SATA disks
> > to AHCI mode. I did not see anything like that. I could select to do a
> > manual config, in which case I could set things like LBA mode, 32-bit
> > I/O (which defaults to off). So if hots wap require AHCI mode, I seem to
> > be screwed. It is a phoenix bios for the supermicro computer.
> 
> The chipset might not support ahci mode.
> 
> > Maybe I can try a different SATA card instead of the stuff on the
> > motherboard. What do you think is the best one re hots waping? Either
> > PCI or PCI-X.
> 
> I primarily use sil3112/4, sil3124/32 and ahci for development.  So 
> those tend to have better support for EH/hotplug stuff.
> 
> >>>>> I bet the driver does the right thing. The trick is knowing what that is
> >>>>> supposed to be. And how to use the various commands on files in /sys at
> >>>>> the correct time and in the correct order.
> >>>> Really, it's not that complicated.
> >>> Once you know what it is you need to do.
> >> I tried hard to make things just work.  If you find things unnecessarily 
> >> complicated, please let me know.
> > 
> > I have a system with an IDE disk with the OS that is fixed. I also have
> > 4 hot swappable SATA disk bays. My use will involve changing the SATA
> > disks to do an analysis of the data they contain. There will be 4 disks
> > in an analysis set. I need to make it easy for the user to insert and
> > remove disks. Rebooting each time is a bad alternative. So, if hot swap
> > does not work, I will have to get warm swap working. I think part of the
> > confusion I have is how to deal with disks that are mounted. So I need
> > to get the steps well defined and make those that require user
> > interaction as few as possible.
> 
> As far as libata is concerned, for warmplug, all you need to use are
> 
>    echo 1 > /sys/class/scsi_device/xxxx/device/delete
> 
> for removal, and for plugging
> 
>    echo - - - > /sys/class/scsi_host/xxxxx/scan
> 
> If you remove device before unmounting, the mounted fs will suffer from 
> io errors and probably spit quite some error messages, so unmounting 
> before is a good idea.

Can the removal echo be done after the disk is physically removed? I
expect not as this seems to confuse things. If this is the case, is
there any way to restore sanity without a reboot?

-- 
Roger Oberholtzer

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