Re: [PLUG] RAID1 impending failure questions

On Fri, Oct 28, 2022 at 7:42 AM Rev. LeRoy Cressy via plug <plug@lists.phillylinux.org> wrote:

The Serial number is not always printed on the Drive. In the old days when
first started using Linux Each drive we bought had the Serial number and the
CHS info on the drive. Now we buy drives that contain 4 to > 16 terabytes in
size. Western Digital does not have the information printed on the drive.

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.

The SATA connections on your motherboard are labeled 0 - ? The drive connected
to SATA 0 should show up as /dev/sda

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

>
> 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.