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Old 08-24-2012, 12:42 AM
John R Pierce
 
Default Order of sata/sas raid cards

On 08/23/12 4:15 PM, Jobst Schmalenbach wrote:
> I will try the LABEL way of doing ....

the problem with labels, there's no guarantee they will be unique. the
default labels that the centos installer uses are the same on every
system, so if you plug a drive into another computer, the odds are
pretty high there will be a collision.

--
john r pierce N 37, W 122
santa cruz ca mid-left coast

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Old 08-24-2012, 02:09 PM
Ken godee
 
Default Order of sata/sas raid cards

I've done that before to get some old data off a drive and
the system appended a "1" to all matching label names.

On 8/23/2012 5:42 PM, John R Pierce wrote:
> On 08/23/12 4:15 PM, Jobst Schmalenbach wrote:
>> I will try the LABEL way of doing ....
>
> the problem with labels, there's no guarantee they will be unique. the
> default labels that the centos installer uses are the same on every
> system, so if you plug a drive into another computer, the odds are
> pretty high there will be a collision.
>

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Old 08-24-2012, 02:24 PM
 
Default Order of sata/sas raid cards

Ken godee wrote:
> I've done that before to get some old data off a drive and
> the system appended a "1" to all matching label names.
>
> On 8/23/2012 5:42 PM, John R Pierce wrote:
>> On 08/23/12 4:15 PM, Jobst Schmalenbach wrote:
>>> I will try the LABEL way of doing ....
>>
>> the problem with labels, there's no guarantee they will be unique. the
>> default labels that the centos installer uses are the same on every
>> system, so if you plug a drive into another computer, the odds are
>> pretty high there will be a collision.
>>
I'll step into this again: let's look at the context.

1. a drive's failed. No conflict.
2. a server's failed, and you want something off one of its disks:
a) you put it in a hot swap bay, and aren't rebooting the server -
you are going to be manually mounting it, so no conflict
b) you need to replace the server in -10 sec: you throw the drive(s)
into a standby box, and either
i. it's got partitions labelled /boot and /; fine, you
*want* it to use those
ii. you want a drive from another disk on that failed
system: no problem - see 2.a.
c) you have a system without hot swap bays, and you install
the drive from the failed system, and then you do have to
power up; this is the only case I can think of, off the
top of my head where you have a collision. In this case,
you need linux rescue, and relabel.

So, where's the big issue with std. labels?

mark

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Old 08-24-2012, 02:49 PM
Les Mikesell
 
Default Order of sata/sas raid cards

On Fri, Aug 24, 2012 at 9:24 AM, <m.roth@5-cent.us> wrote:
> > I'll step into this again: let's look at the context.
>
> 1. a drive's failed. No conflict.
> 2. a server's failed, and you want something off one of its disks:
> a) you put it in a hot swap bay, and aren't rebooting the server -
> you are going to be manually mounting it, so no conflict
> b) you need to replace the server in -10 sec: you throw the drive(s)
> into a standby box, and either
> i. it's got partitions labelled /boot and /; fine, you
> *want* it to use those
> ii. you want a drive from another disk on that failed
> system: no problem - see 2.a.
> c) you have a system without hot swap bays, and you install
> the drive from the failed system, and then you do have to
> power up; this is the only case I can think of, off the
> top of my head where you have a collision. In this case,
> you need linux rescue, and relabel.
>
> So, where's the big issue with std. labels?

You power down, add some disks that you want to re-use. Maybe even
add a controller. Just because a bay looks like you can hot-swap
doesn't mean it is a good idea if you don't have to. You boot up.
When the label scheme was first rolled out, the machine wouldn't boot
if it found a duplicate. Now it will pick one. Possibly the wrong
one. As you might when you do a rescue boot for the relabel since you
won't know which controller is detected first.

--
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Old 08-24-2012, 03:04 PM
 
Default Order of sata/sas raid cards

Les Mikesell wrote:
> On Fri, Aug 24, 2012 at 9:24 AM, <m.roth@5-cent.us> wrote:
>> > I'll step into this again: let's look at the context.
>>
>> 1. a drive's failed. No conflict.
>> 2. a server's failed, and you want something off one of its disks:
>> a) you put it in a hot swap bay, and aren't rebooting the server -
>> you are going to be manually mounting it, so no conflict
>> b) you need to replace the server in -10 sec: you throw the
>> drive(s)
>> into a standby box, and either
>> i. it's got partitions labelled /boot and /; fine, you
>> *want* it to use those
>> ii. you want a drive from another disk on that failed
>> system: no problem - see 2.a.
>> c) you have a system without hot swap bays, and you install
>> the drive from the failed system, and then you do have to
>> power up; this is the only case I can think of, off the
>> top of my head where you have a collision. In this case,
>> you need linux rescue, and relabel.
>>
>> So, where's the big issue with std. labels?
>
> You power down, add some disks that you want to re-use. Maybe even
> add a controller. Just because a bay looks like you can hot-swap
> doesn't mean it is a good idea if you don't have to. You boot up.

Okayyyy... We differ, here - I've come to adore hot-swap bays, and hate
having to take a system apart to add another drive.

Reused disks - I reformat them, usually in a hot swap bay.

Of course, I *do* have some additional concerns - I have to worry about
PII and HIPAA data that may, *possibly*, be on the drives.

> When the label scheme was first rolled out, the machine wouldn't boot
> if it found a duplicate. Now it will pick one. Possibly the wrong
> one. As you might when you do a rescue boot for the relabel since you
> won't know which controller is detected first.

But you can do a rescue, mount, and look at what's on what the controller
found.

mark

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Old 08-24-2012, 03:18 PM
Les Mikesell
 
Default Order of sata/sas raid cards

On Fri, Aug 24, 2012 at 10:04 AM, <m.roth@5-cent.us> wrote:
>
>>> So, where's the big issue with std. labels?
>>
>> You power down, add some disks that you want to re-use. Maybe even
>> add a controller. Just because a bay looks like you can hot-swap
>> doesn't mean it is a good idea if you don't have to. You boot up.
>
> Okayyyy... We differ, here - I've come to adore hot-swap bays, and hate
> having to take a system apart to add another drive.

Same here, in terms of the actual swap. But I'm old enough to
remember electronics that were sensitive to static, power
fluctuations, etc., so I generally power down while doing it. And I
don't want to create a scenario where the machine might do something
unexpected if it did happen to reboot with the disks added.

> Reused disks - I reformat them, usually in a hot swap bay.

Same here, but I've had unwanted surprises from duplicate labels
before the format. Hence the conclusion that duplicate labels are as
bad and idea as duplicate hostnames, IP addresses, or any other
identifier would be.

> Of course, I *do* have some additional concerns - I have to worry about
> PII and HIPAA data that may, *possibly*, be on the drives.

I normally don't have to worry about contents unless the disks leave the site.

>> When the label scheme was first rolled out, the machine wouldn't boot
>> if it found a duplicate. Now it will pick one. Possibly the wrong
>> one. As you might when you do a rescue boot for the relabel since you
>> won't know which controller is detected first.
>
> But you can do a rescue, mount, and look at what's on what the controller
> found.

And they all look alike...

--
Les Mikesell
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