[Novalug] SATA HD with LVM on RAID/ udev needed?

RJ Bergeron rbergero@gmail.com
Sun Jun 29 19:46:01 EDT 2008


On Sun, Jun 29, 2008 at 19:26, Brandon Saxe <brandon20va@yahoo.com> wrote:
> ?- My SATA controller is a Silicon Image and hot swap is supported. Is there any special thing I need to do to let the kernel know when I am about to remove/insert a drive (of course after unmounting any filesystem first). Is it okay to just 'umount' and unplug? Does 'eject' matter here or maybe there's some SCSI commands I should issue? I am not sure.
I've not played with the eject code, I heard it is working these days
for SATA, but don't have anything I'm willing to try it with.
According to http://linux-ata.org/software-status.html (Search for
'hotplug supprt'), you just yank it... I'm not sure how the SATA
backplane deals with this, if at all.

> ?- Device Names. Depending on the order the drives are inserted/removed, the device name changes from anything between /dev/sdd to /dev/sdf. I have also seen /dev/sdg on testing. For reference, I have two other SATA drives attached to mobo at /dev/sda and /dev/sdb. /dev/sdc is a USB drive. Do I need to configure udev rules for each drive in order for my system to function correctly? OR will RAID and LVM figure all that out for me?
Linux's MD software writes a signature to each disk and uses that to
figure out how to assemble the RAID. This lets you do very silly
things like swap out PATA controllers for a stack of USB->PATA
boxes...

> ?- Should I bother dealing with udev on this one? Even if RAID and LVM don't care about device names, I still feel it may be helpful to know exactly which drive is at which device node. Can anybody recommend why I *should* or *shouldn't* do udev?
I would stay away from configuring udev to map drives statically, it's
just not necessary and may confuse the MD assembly processes ('seeing'
things twice). I actually recently replaced a failed drive (through
coldplug, ATA100 here...) by noticing the actual failed device in
/proc/mdstat, then running smartctl -a /dev/hde (my device) so I knew
which model/serial number I needed to pull.

RJ



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