Re: [gentoo-user] OT:Choosing a filesystem

[Paul Hartman]

On Fri, Apr 2, 2010 at 4:55 PM, Mark Knecht <markknecht@×××××.com> wrote:
> On Fri, Apr 2, 2010 at 2:49 PM, Paul Hartman
> <paul.hartman+gentoo@×××××.com> wrote:
>> On Fri, Apr 2, 2010 at 2:50 PM, Volker Armin Hemmann
>> <volkerarmin@××××××××××.com> wrote:
>>> On Freitag 02 April 2010, Neil Bothwick wrote:
>>>> On Fri, 2 Apr 2010 20:40:54 +0200, Volker Armin Hemmann wrote:
>>>> > > LVM and RAID are completely different animals. No one suggested using
>>>> > > it for any reasons of data security, running LVM on a RAID array
>>>> > > gives both security and flexibility. As for being able to add space
>>>> > > to RAID, you can't temporarily add a new volume whenever you want,
>>>> > > you have to go out and buy another drive, then power down the
>>>> > > computer to fit it, assuming there is room in the case for an extra
>>>> > > drive.
>>>> >
>>>> > no need to power down - and you can add and remove drives. Read man
>>>> > mdadm.
>>>>
>>>> Assuming your controller supports hotplugging, assuming you have a drive
>>>> available to plug in, assuming you are able to physically add a drive.
>>>
>>> sata can hotplug. all ahci controlers can hotplug and all sata drives can
>>> hotplug. If you insist on technology straight from the stone ages that is your
>>> problem.
>>
>> Do you know if it's necessary to signal to the system (like /proc/scsi
>> something) that I'm about to unplug the drive, and in which order the
>> power/data need to be disconnected to prevent a problem? I'm curious
>> in case of future need. :)
>>
>> Thanks.
>
> If it's part of a RAID the new one gets rebuilt.
>
> If it's not part of a RAID then I think, as per Neil's example, the
> computer is pretty much dead, right? However if you wanted to try it
> (and I'm not brave enough so don't listen to me) then you might want
> to do something like
>
> grep -A 1 dirty /proc/vmstat
>
> and wait until nothing is dirty.
>
> Just an idea,

Well, forgetting about RAID and bad drives, I should be able to
unmount a normal, working SATA drive and unplug it safely, just like
with a USB hard drive. I just don't know if you have to signal to
SATA/AHCI that you're going to unplug (like with old hot-swappable
SCSI drives), or if you need to unplug data cable before unplugging
the power cable, for example.