I agree with your view on the asmlib/udev matter. I like udev over asmlib, but if you are not able to manage udev, asmlib will probably do without much heavy linux lifting. From what I've seen Oracle did not fork a kernel of their own. They just rolled a kernel of their own, just like every distro does. I don't understand the hassle around it. Anyone can download the kernel source and roll a kernel of their own. Probably the reason lies in in some stuff needed by the database machine (OFED/infiniband, the # processors/cpu threads, NUMA), so some tweaked stuff. But really, what is the deal? Frits Hoogland http://fritshoogland.wordpress.com mailto: frits.hoogland@xxxxxxxxx cell: +31-6-53569942 On Oct 26, 2010, at 11:30 PM, Jeremy Schneider wrote: > Yes, both udev and asmlib are integrated into the kernel. Asmlib is not > distributed by redhat in the kernel rpm, so as you have pointed out, it needs > to be kept in sync. This would be the case for any kernel modules installed > separately. I have also occasionally seen network or hba drivers that are > installed separately and require separate maintenance with any kernel > upgrade. On a side note, I bet that this will change in the new Oracle > kernel - quite likely you won't need the separate step anymore, now that > Oracle has officially forked their own kernel. > > I was involved in the engineering effort at a very large org and we decided > to use udev. (In fact, I was one of the main proponents of this approach.) > It has in fact fallen by the wayside since I left, because noone else can > figure out how to write those cryptic udev rules. One of the major problems > was that for every new device that came along, we had to figure out new udev > rules to detect this device. (New HBA vendor, new multipath driver, new SSD > card, etc.) As long as I was around to reverse engineer what kinds of kernel > rules we needed to write, it was fine. But noone else could really figure it > out. With Asmlib, there's no new effort for new devices - any block device > is just as easy to work with. > > Personally, I love the flexibility and control of udev. But I really do > think it's a bear to learn - you pretty much have to understand basic linux > kernel internals to get it... there are some people out there who can do > that, but not everyone can. I think that (for better or worse) pretty much > anyone can use Asmlib. > > -Jeremy > > > David Robillard wrote: >> >> Hello Jeremy, >> >> On Tue, Oct 26, 2010 at 4:32 PM, Jeremy Schneider >> <jeremy.schneider@xxxxxxxxxxxxxx> wrote: >> >>> David Robillard wrote: >>> >>>> Should you decide to use ASM, I strongly suggest to stay away from ASMLib >>>> and use udev instead. >>>> >>> I'm a little curious about the reasoning for this. I wrote a few blog >>> posts (long ago) about uncertainty in the state of ASMLib... but these >>> days I'm not so convinced anymore that it's worth avoiding. >>> >> >> Unless things have changed since last summer, I think the main reason >> to stay away from ASMLib is because it's a kernel module which depends >> on the exact kernel version the machine was running on when ASMLib was >> installed. That creates a problem when a kernel upgrade happens and >> you reboot the machine. If you forgot to update ASMLib, then it won't >> load because the kernel version changed. What you end up with is no >> ASM disks :( >> >> That's not a problem with udev(8) because it's independent of the >> kernel version. Which means you can upgrade your kernel, udev will >> still do it's job and you won't have any ASM disk problem. >> >> One other thing I like with udev is that it's part of the official >> RedHat (or OEL) release. So when a bug fix/enhancement happens to >> udev, you benefit from it from the standard OS maintenance procedure. >> With ASMLib, you have to keep an eye on the Oracle website. IMHO, it's >> easier to maintain software when it's part of the OS. >> >> Of course if you use ASMLib and have clear standard operating >> practices and clear documentation that says you should update ASMLib >> each time you upgrade a kernel, then I guess it's fine. But most >> companies I've seen don't have that kind of rigid update procedures. >> More often, the person in charge of ASM is not the same as the one in >> charge of keeping the OS up to date. That situation can lead to >> problems with special kernel modules like ASMLib. >> >> >>> UDEV is kinda nice if you understand it... but the documentation is poor and >>> frankly I've met precious few who do understand it. I tend to tell most >>> people now to just use ASMLib unless they already know UDEV. >>> >> >> Well, ok, udev's documentation may not be very easy to grasp at first. >> But it's not that difficult either. And once you have it up and >> running, maintenance is easier then ASMLib. >> >> I've always wanted to blog about how to setup udev so that people have >> a clear document how to set it up. But until I can find the time and >> if you're curious, Freek D'Hooge and I had a long thread on this list >> about the configuration of udev. You can find the thread archive here: >> >> //www.freelists.org/post/oracle-l/OCR-VD-external-vs-normal-redundancy-using-NFS,13 >> >> >> >>> I'm skeptical that it's worth the time required to learn it. >>> >> >> That depends. A day or two learning udev might look like long. But >> they're nothing compared to the time and stress required to debug a >> node that comes up with no ASM disks because of a kernel version >> mismatch with ASMLib. You also have to calculate the time required to >> check for new ASMLib versions on Oracle website, download and install >> it compared to a standard OS upgrade with yum(8) when you use udev. >> But, as always, YMMV. >> >> Let me know if that answers your question? >> >> Cheers, >> >> David >> -- >> http://ca.linkedin.com/in/davidrobillard >> >> > > > -- > http://www.ardentperf.com > +1 312-725-9249 > > Jeremy Schneider > Chicago