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DRBD To Be Included In Linux Kernel 2.6.33
An anonymous reader writes "The long-time Linux kernel module for block replication over TCP, DRBD, has been accepted as part of the main Linux kernel. Amid much fanfare and some slight controversy, Linus has pulled the DRBD source into the 2.6.33 tree, expected to release February, 2010. DRBD has existed as open source and been available in major distros for 10 years, but lived outside the main kernel tree in the hands of LINBIT, based in Vienna. Being accepted into the main kernel tree means better cooperation and wider user accessibility to HA data replication."
The "DR" stands for Distributed and Replicated. DRBD is way higher-level in function, but integrated lower-level than the simple userspace daemon that the server side of NBD uses.
Read the docs, the differences should be blindingly obvious.
We use DRBD for some very mission critical servers that require total redundancy. Combined with Heartbeat I can fail over from one server to another without any single point of failure. We've been using it for more then 5 years, and never had any major issues with it. It will be great to have it in the mainline kernel.
Why is it so hot? Where am I going? What am I doing in this handbasket?
It's a kernel module. Don't like it, don't load it.
Your "requirement": "something that the majority of Linux users need, or want" is irrelevant. There are LOTS and LOTS of drivers in the kernel for which this is true, probably MOST of them.
"it's just another layer of complexity" - NOT if you don't install the userland packages or load the kernel module.
"Personally" - you got a lotta nerve representing yourself as having a valid opinion about what does and does not constitute a useful feature.
A closed mouth gathers no foot.
Doing it in software for purely virtual hardware is useful. I know it's been used to sync disks across the network on Xen hosts, the idea being that if the local and remote copies of the disk are kept in close sync, you can migrate a virtual machine with very low latency. Should be able to do similar tricks with other Linuxy VMMs. Having software available to do this stuff makes it easy to configure this sort of thing quickly, especially if you're budget-constrained, hardware-wise.
You want "make localmodconfig", which I think was also added recently, possibly to 2.6.32 actually. This builds a kernel using a local .config file, except that it only compiles modules that show up in lsmod. So if you boot off your vendor kernel with a squillion modules, let it load the modules you actually *use* then do make localmodconfig, you can make a kernel that only contains those modules. I don't know what it does if module names etc change, maybe you'd need manual fixup then - should still be less work than you currently are doing though.
There's some explanation here, though it might be for an out-of-date version of the patch:
http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-09/msg04230.html
As the other reply said, make oldconfig is also useful to important settings from a previously configured kernel, can save a lot of time.
You should consider a career as a teacher.
And then you should shoot yourself in your fucking brainpan.
I admin AIX systems for my day job... One thing that's really nice about AIX is that the filesystem and underlying block device is highly integrated. This means that to resize a volume you can run a single command that does it on the fly. For AIX admins who are new to Linux it seems a step backwards and they liken it to HP-UX or some earlier volume management...
Ahh, but the beauty of having separate filesystem and block device is that it's so damn flexible. I can build an LVM volume group on iSCSI LUNs exported from a another system. In that VG I can create a set of LUNs that I can use for the basis of my DRBD volume. In that DRBD volume I can carve out other disks. Or I can multipath them. Or create a software RAID.
Anyhoo, DRBD is a really cool technology. It gives the ability to create HA pairs on the cheap. You can put anything from a shared apache docroot there to the disks for Oracle RAC. With fast networking available for cheap, almost any shop can have the toys that were once only affordable to big companies...
I dont like drbd (though i've used it for a while)... its a massive convoluted and complex mess and fairly inflexible.
Personally, im hoping dm-replicator gets near completion sometime soon though details of it are rather scarce (i do have a kernel built with the dm-replicator patches, but trying to do anything with it seems near impossible)...
I do a fair amount of work inside the storage world and drbd is just such a mess in so many ways.
I sounds very critical and so forth to drbd and thats not the way i mean to come across. What I really am trying to say is that its bloated for the small amount of functionality it does and with a couple of minor tweeks could do much MUCH more. Its a kewl piece of software, but like many FOSS projects has a hideous, weighty config prone to confusion (something you just dont need with DR).
Still, that is the way it is!
They are called modules for a reason: You can add or remove at will, including whether or not you bother to build them at all. To say modules are "built into the kernel" is incorrect; module code is included with the kernel source code, but the modules themselves are only built and used if you choose.
As concerns the "insanity" of configuring a kernel, here again you have a choice: Use Ubuntu. But if you want a fast, lean, mean machine you really do want to craft your kernel to fit your specific needs.
Everything in the Universe sucks: It's the law!
I'm not about to dismiss your experience, but things have changed over the last 15 years so it might not be as relevant as it once was.
In that time processors have become much faster, memory has become much cheaper, commodity servers have also become much cheaper and a lot of software has become free. While that has happened hard disks have become only a little faster. As a result many people consider custom hardware for driving those disks to be unnecessary - generic hardware is more than fast enough and is significantly cheaper.
There might still be some compelling reasons to go with expensive redundant SAN equipment, but for many situations a couple of generic servers full of disks and running Linux and DRBD will do an admirable job. The bottleneck will most likely be the disks or the network, both of which can be addressed by spending some of the vast amount of money saved by not going with typical enterprise solutions.
i'm sorry to say, but that's not a good attitude. and i'm being polite here.
developers need testers. some arrogant assholes might claim they don't, but then they're known as ones. now, to attract testers you not only are polite to them, you also do not discourage them by breaking or ignoring things that hamper them (but might not concern casual users), you actually should build tools and other support functionality for testing.
essentially, having less testers will impact quality of the software for everybody else, so casual users also should desire for the project to have more testers.
i'm glad that at least some kernel hackers recognise this, and 2.6.32 actually has support for new configuration method, which looks at already loaded modules and some other stuff to create trimmed down kernel config - http://kernelnewbies.org/LinuxChanges#head-11f54cdac41ad6150ef817fd68597554d9d05a5f
Rich