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

[Mark Knecht]

On Fri, Apr 2, 2010 at 3:03 PM, Paul Hartman
<paul.hartman+gentoo@×××××.com> wrote:
> 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.
>
>

I've never done it but according to the SATA spec yes. As with all
drive umount first. Nothing I've read says it's truly safe to do it
too many times. It's easy to damage or wear out the connectors or the
drive.

It's the #1 'end-user benefit' according to the SATA spec web pages:

http://www.serialata.org/technology/why_sata.asp

- Mark