[ale] one kernel module, multiple devices

Fri May 16 15:48:53 EDT 2014

Are you sure your “HBA” is using the mp2sas driver?   Tape drives aren’t typically SAS in my experience nor do they typically allow for multiple paths like disk drives do so there would be little reason to put them on a RAID style controller.

Here we use the PERC (LSI OEM) on Dell but if we’re doing disk array or tapes we’re presenting them via Qlogic fibre HBAs.

I’m curious what software you have that lets you manage the LSI RAID from the OS level.

From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Jim Kinney
Sent: Friday, May 16, 2014 2:22 PM
To: Atlanta Linux Enthusiasts
Subject: Re: [ale] one kernel module, multiple devices

I see what you're saying. I have 2 different controller cards however. One is a RAID the other is an HBA. But they both use the same driver. I have software that lets me control the RAID array through the card but an HBA is "dumb" of sorts. It's best to disconnect the HBA from the tape system before powering down the tape system but I don't think I can do that without unloading the kernel module which will force a disconnect from the RAID array (so I may as well power down the entire system - grr).

On Fri, May 16, 2014 at 2:04 PM, Lightner, Jeff <JLightner at dsservices.com<mailto:JLightner at dsservices.com>> wrote:
Since the controller is presenting the RAID LUNs (virtuals disks) rather than the real physical disks as “disks” to the OS I wouldn’t think you could control it from the OS level at all.   That is to say if you have a RAID 5 LUN comprised of 4 disks on one channel of the LSI controller and a RAID 1 LUN comprised of two disks on the other channel of the LSI controller the OS is actually only seeing 2 “disks” which are actually the two LUNs (a/k/a virtual disks) rather than all 7 physical disks.    That is different from software RAID where you see all the physical disks and assemble them into meta-disks.

The only time I’ve been able to adjust RAID setup on LSI (or Dell’s PERC OEM of same) is during the boot when I enter the BIOS of the adapter itself.   I have seen later versions of Dell BIOS call this as well but that still requires that I did the Dell BIOS during boot up.   I’ve  also seen some view of the PERC setup via Dell OpenManage but as I recall that was more a view than a way to manipulate layout.

From: ale-bounces at ale.org<mailto:ale-bounces at ale.org> [mailto:ale-bounces at ale.org<mailto:ale-bounces at ale.org>] On Behalf Of Jim Kinney
Sent: Friday, May 16, 2014 1:47 PM
To: Atlanta Linux Enthusiasts - Yes! We run Linux!
Subject: [ale] one kernel module, multiple devices

I have a system with multiple SAS devices. They all are LSI and use the same kernel module - mpt2sas.
I would like to be able to disconnect one device from the module while leaving the other attached and running. This way I can drop a SAS HBA running a tape system so I can power down the tap and pull out a drive with a stuck tap all without disturbing the RAID card and it's mounted files (i.e. the OS!).
I know the PCI bus addresses but have not found a way to unload a shared module without fully unloaded a shared module.
Ideas?

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James P. Kinney III

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- Speech 11/23/1900 Mark Twain

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--
--
James P. Kinney III

Every time you stop a school, you will have to build a jail. What you gain at one end you lose at the other. It's like feeding a dog on his own tail. It won't fatten the dog.
- Speech 11/23/1900 Mark Twain

http://heretothereideas.blogspot.com/
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