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ufmale 05-27-2008 12:48 PM

sda sdb sdc drives not consistent
My company has a disk enclosers for 10 disks that can be used for RAID.
I am doing an experiment where i have only 3 disks in the slots.

After booting the linux machine and load the driver (for RAID pci card), I can see those 3 disks-- sda, sdb, and sdc-- using "fdisk -l"

I took sdb drive out of the tower, then call "fdisk -l".
Now I see only sda and sdc as expected.

Then i put the sdb back to the same slot and call "fdisk -l"
Now I see sda, sdc, and sdd.

Is this how it is supposed to work, or it is a bug of the RAID pci driver?

bigrigdriver 05-27-2008 12:53 PM

I don't know if this makes a difference or not, but, did you unmount the partitions on sdb before removing it from the rack? Did you re-mount the partitions when you put it back in the rack, before running fdisk?

ufmale 05-27-2008 03:35 PM

No. I didn't umount any drive when taking it out of the rack since i try to simulate a disk failure. Plus, the tower say it support a hot swap.

When i put back the drive and see the sdc. I can probably mount /dev/sdd but i wonder why it does not detect the drive as sdb.

bigrigdriver 05-27-2008 04:44 PM

Well, since it doesn't seem to be hot swapping quite as expected, perhaps a question sent to the vendor is in order.

As a test, try removing sdb to simulate disk failure. Then try taking the system down before re-inserting the drive. If it comes back as sdb, then you have evidence that the system isn't hot swappable as advertised.

You can either get a tower that works as advertised, or you should be able to get a partial refund for money paied in good faith for goods that don't live up to the advertisment.

czarr 05-27-2008 04:49 PM

I have a similar experience with usb sticks (the only thing that changes in my /dev) and i have noticed that it can mount sdc the first time and sdd the second (yes i'm mount-ing and umount-ing) maybe this is a problem with linux and not your hardware.

Emerson 05-27-2008 04:53 PM

Udev is assigning new device node, I'm not sure if using udev in a server is good idea at all. Plus, since Linux can see separate disk drives through your "RAID" controller then you obviously do not have hardware RAID. So the first question to answer here is what software RAID is in use?

largem 05-27-2008 06:38 PM

udev has some rules to make the device name to be persistent. You could find some pre-defined rules in SLES10. I think it might resolve this problem.

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