Re: [PLUG] RAID1 impending failure questions

[Walt Mankowski via plug <plug@lists.phillylinux.org>]

On Fri, Oct 28, 2022 at 08:38:34AM -0700, Rich Mingin (PLUG) via plug wrote:
> While it is true that OEMs are no longer printing CHS information on the
> label (as modern drives cannot be connected to a PATA controller to work as
> a very dumb non-LBA sub-2/8GB drive this information is worthless), but in
> the last 30 years I have not ever heard of a drive that does not have the
> serial number in a label on the drive or etched into the metal. A drive
> without an externally readable serial number would be completely useless to
> the OEM, since they would have to cover *every* drive they made until the
> last one was shipped+the full warranty length, as you would not be able to
> tell two non-working drives apart. I suggest you recheck the label, with
> your reading glasses on. I am certain the serial number is there somewhere.

Thanks. that was certainly my hope. If not, then I figured I'd look
for connections on the motherboard, but I was really hoping I wouldn't
have to.

> This is a dangerous assumption and should not ever be trusted. While it is
> the ideal, both SATA and PATA enumerate disks in the order that they are
> “seen” by the OS, and this has always been the case. You can get away with
> assuming SATA port 0 is likely /dev/sda most of the time, but SATA port 5
> is not always /dev/sdf. It’s better to use UUIDs, labels, or other
> “smarter” methods to ID disks, especially in a degraded mirror where one
> mistake can result in major

I'm going to save as much info about the 2 drives as I can before I
try this. Since the drive isn't failing (yet) I suppose I could try
just unplugging one of them, but obviously I'd like to try to avoid
that unless as a last resort.

> 
> >
> > > Second question -- Let's say I remove the old drive, install the new
> > > drive and it's sde1. Will the system think it's a RAID1 with one drive
> > > and just use that until I add sde1 to the array?
> >
> > That will depend on the initial Raid configuration.
> > Also just plugging in a new drive will not necessarily mean that it is
> > formatted with either GPT or MBR.  With every new drive I run gparted or
> > what
> > ever partitioning program is your favorite.  I have noted that most drives
> > still come with MBR partitioning installed on them by default.
> 
> 
> 
> New drives should not be formatted. With the exception of USB externals, I
> haven’t seen a factory-formatted HDD in many years. Have you been buying
> factory-formatted? What brand/model/size? I’d like to avoid those.

I'm not sure if I have either, but it's been 6 years since I've had to
mess with any of this stuff, so I'm basically relearning all of it all
over again. I'd certainly want the partitioning to match the other
drives in any event.

Walt
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