You might want to check out raidreconf (http://unthought.net/raidreconf/ which will allow you to add disks (although it's rather slow) to a RAID-0 or RAID-5. I cover this in the book, to a certain degree.
I do agree though, you hit on some issues with the md driver. There have been some recent discussions on linux-raid about how to help integrate RAID and LVM in the context of EVMS and other user space tools. I think that by this time next year, a lot of the mess/overlap between the two will be cleaned up.
One careful consideration with ATA RAID is that many of the controllers are not really hardware RAID. I don't think this is the case with the SX4000, but many low-end ATA RAID controllers (especially the on-motheboard flavors) are just software RAID in disguise.
Derek Vadala
Re:I know this book is about software RAID ...
on
Managing RAID on Linux
·
· Score: 3, Interesting
There are plenty of reasons to go software RAID over hardware RAID. With Linux, one of the main reasons is the same reason many of us choose Linux to begin with-- it's open source. I know that isn't traditionally a factor to be considered when picking hardware, but remember that when a hardware controller fails you are at the mercy of the vendor. If a Linux software RAID fails, you have access to the source code and perhaps also the developers, so maybe you just have a shot at recovering data in a catastrophic event, even if it does mean writing some recover tool on your own. In fact, with RAID-1 in the Linux kernel, if something goes kablooey you can just mount a member disk standalone and get some rest.
That's only one consideration. It used to be that the headache of booting from, and installing to Linux with software RAID was a huge hassle. Today almost every distribution supports out of the box installation to software RAID. So the 'ease of use' considerations for going hardware are all but gone.
Now here's the issue that always starts the tug of war-- performance. Traditionally hardware RAID was simply better because it didn't hit the CPU. Today that doesn't make a difference, especially if you use SCSI. Now with ATA you might see the overhead of RAID a little more, but that's because ATA already has overhead to begin with. The CPU hit with SCSI is negligible, and I doubt if it will be noticed in most cases, even in so called "production". That's because the real bottleneck in most systems in I/O throughput and not CPU performance. That's most systems, not all systems. Obviously if you are a good sysadmin you are evaluating these issues on a case by case basis.
Finally I just want to say that it's a widely held opininion among the Linux RAID community that the kernel RAID (the md driver) outperforms all but the most high-end SCSI RAID controllers. I'm sure many will disagree, but that's been my experience and I know that if you ask certain kernel developers who shall remain nameless they will tell you the same thing.
No single task is more essential to our continued survival. Without the creation of optimized synthesized lifeforms, charged with the task of interacting with our environment in a way that eliminates the uncontrollable byproducts created by humans during the last 250 years, we will pluge the planet into an unrecoverable tempest of biologically hazardous miasma. Clealy the only way to correct this situation is through the synthesis of organism that can safely use our industrial and organic byproducts as an energy source, thus correcting an ecological imbalance caused by industrialization and overpopulation.
One of the biggest hacks of all time was using an Air Force computer to house the Dead of Night chat system back in 1989. Remeber that? Probably not, because all you punk ass kids were sucking on mom's teets.
This bullshit about a hack having to do with swift programming ability, well.. sure... but that's not what the colloquailism is and you all need to get over this meta-progammer bullshit.
Re:Don't abandon your language classes anytime soo
on
Universal Translators?
·
· Score: 1
A long time? What's this amount to, 15 or 20 years? It's not like this is a project that has eluded humanity for centuries. Breakthroughs are always just around the corner. Maybe your friend has given you good reason to play skeptic. The again, maybe he's not the one who makes the breakthrough. By the power of Greyskull! I invoke Moore's Law!
Slashdot Mirror
You might want to check out raidreconf (http://unthought.net/raidreconf/ which will allow you to add disks (although it's rather slow) to a RAID-0 or RAID-5. I cover this in the book, to a certain degree.
I do agree though, you hit on some issues with the md driver. There have been some recent discussions on linux-raid about how to help integrate RAID and LVM in the context of EVMS and other user space tools. I think that by this time next year, a lot of the mess/overlap between the two will be cleaned up.
One careful consideration with ATA RAID is that many of the controllers are not really hardware RAID. I don't think this is the case with the SX4000, but many low-end ATA RAID controllers (especially the on-motheboard flavors) are just software RAID in disguise.
Derek Vadala
There are plenty of reasons to go software RAID over hardware RAID. With Linux, one of the main reasons is the same reason many of us choose Linux to begin with-- it's open source. I know that isn't traditionally a factor to be considered when picking hardware, but remember that when a hardware controller fails you are at the mercy of the vendor. If a Linux software RAID fails, you have access to the source code and perhaps also the developers, so maybe you just have a shot at recovering data in a catastrophic event, even if it does mean writing some recover tool on your own. In fact, with RAID-1 in the Linux kernel, if something goes kablooey you can just mount a member disk standalone and get some rest.
That's only one consideration. It used to be that the headache of booting from, and installing to Linux with software RAID was a huge hassle. Today almost every distribution supports out of the box installation to software RAID. So the 'ease of use' considerations for going hardware are all but gone.
Now here's the issue that always starts the tug of war-- performance. Traditionally hardware RAID was simply better because it didn't hit the CPU. Today that doesn't make a difference, especially if you use SCSI. Now with ATA you might see the overhead of RAID a little more, but that's because ATA already has overhead to begin with. The CPU hit with SCSI is negligible, and I doubt if it will be noticed in most cases, even in so called "production". That's because the real bottleneck in most systems in I/O throughput and not CPU performance. That's most systems, not all systems. Obviously if you are a good sysadmin you are evaluating these issues on a case by case basis.
Finally I just want to say that it's a widely held opininion among the Linux RAID community that the kernel RAID (the md driver) outperforms all but the most high-end SCSI RAID controllers. I'm sure many will disagree, but that's been my experience and I know that if you ask certain kernel developers who shall remain nameless they will tell you the same thing.
Run bonnie, you'll see.
Derek Vadala, lowly author.
No single task is more essential to our continued survival. Without the creation of optimized synthesized lifeforms, charged with the task of interacting with our environment in a way that eliminates the uncontrollable byproducts created by humans during the last 250 years, we will pluge the planet into an unrecoverable tempest of biologically hazardous miasma. Clealy the only way to correct this situation is through the synthesis of organism that can safely use our industrial and organic byproducts as an energy source, thus correcting an ecological imbalance caused by industrialization and overpopulation.
One of the biggest hacks of all time was using an Air Force computer to house the Dead of Night chat system back in 1989. Remeber that? Probably not, because all you punk ass kids were sucking on mom's teets.
This bullshit about a hack having to do with swift programming ability, well.. sure... but that's not what the colloquailism is and you all need to get over this meta-progammer bullshit.
A long time? What's this amount to, 15 or 20 years? It's not like this is a project that has eluded humanity for centuries. Breakthroughs are always just around the corner. Maybe your friend has given you good reason to play skeptic. The again, maybe he's not the one who makes the breakthrough. By the power of Greyskull! I invoke Moore's Law!
This is a decent starting point for disassembly information. Lot's of texts on reverse engineering, with pointers to tools, etc...
mammon_