Hi, I have a client that insists on going with software rather than hardware raid1 to save a few dollars. Can Centos 4.2 do Boot and Root on software Raid1? I've heard criticisms of Grub and bootable RAID. Also, if it is not set up to work out of the box, I'd like to try to talk them out of it. I've been down that road before. If I go nonstandard, by the time I actually need to boot from the second drive in an emergency, I've forgotten the special procedure. (Why can't businesses just spend a few extra dollars to do things right?!) Thanks for any info. -Steve
Just some additional info that I should have included in my original post. This would be SATA raid using the onboard SATA interfaces on a Dell Poweredge SC1420 server. They call it a "Software RAID" controller, but I think that just means they give you 2 SATA channels and your OS can do the RAID part.
Quoting Steve Bergman <steve at rueb.com>:> Hi, > > I have a client that insists on going with software rather than > hardware raid1 to save a few dollars. > > Can Centos 4.2 do Boot and Root on software Raid1?Yes on i386. No on ia64 (partition where /boot dir is can't be on RAID-1). Don't know for x86_64 (should be).> I've heard criticisms of Grub and bootable RAID. Also, if it is not > set up to work out of the box, I'd like to try to talk them out of it.Yes, Anaconda had this long standing bug of not handling /boot on RAID-1 properly when installing Grub. With LILO it worked perfectly for a very long time out of the box. I don't know if Anaconda/Grub problem was fixed recently. Even if it wasn't it is relatively trivial to adjust grub configuration and install it on both drives.> I've been down that road before. If I go nonstandard, by the time I > actually need to boot from the second drive in an emergency, I've > forgotten the special procedure.Depending on the type of failure, special procedure might not be needed. Even if it is, it is relatively trivial (and I wouldn't really call it special procedure) ;-) ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
On Thu, 2005-10-20 at 09:59, Steve Bergman wrote:> I have a client that insists on going with software rather than hardware > raid1 to save a few dollars.Software raid some advantages of its own.> Can Centos 4.2 do Boot and Root on software Raid1? > > I've heard criticisms of Grub and bootable RAID. Also, if it is not set > up to work out of the box, I'd like to try to talk them out of it.It doesn't install by itself but the grub setup only has to be done once manually.> I've been down that road before. If I go nonstandard, by the time I > actually need to boot from the second drive in an emergency, I've > forgotten the special procedure.The nature of software RAID is such that you can pretend it wasn't there and use a single drive like a single drive. Thus, in the worst case of a boot problem you would take whichever drive looked the most likely to work, connect to a controller position that is configured to boot, and do what you would do with a single drive. That means if you had pre-installed grub on the second drive it will just work. If you haven't, you can boot with the install CD in rescue mode, chroot where it tells you, and do a grub-install just like you would with any other drive.> (Why can't businesses just spend a few extra dollars to do things right?!)Often it is because for the extra money, you get no extra features except being locked into some particular vendor's product. With software RAID1 you can pull out any single disk and recover the data on any machine with a similar interface type. With a raid controller, if the PC or controller fails you'll have to have exactly the same model to ever access those drives again - and you may or may not have the tools to observe the status and 'smart' condition of the drives and to rebuild the mirrors online. -- Les Mikesell lesmikesell at gmail.com
I've not yet tried Software RAID 1 with Centos 4.x but I've done so with Fedora Core 1 / X86-32 so I'd assume that my comments would apply. I tend to prefer software RAID simply because then I'm not locked to a specific vendor/controller. If a hardware failure occurs that takes out the controller but leaves at least one of the HDDs ok, I can take one software RAID HDD, stick it into another controller, and have a working system in very short order. Hardware RAID frequently does not have this advantage. When I've set up RAID, I did so with the RH installer, and have always picked RAID1. (RAID5 is a joke for SW RAID) I've set up a number of RAID installs with "boot/root" and extensions using the Software RAID howto. (google it) Experimentally, I've set up a RAID array, removed one drive, booted, shutdown, and then replaced it with the other. Both drives booted fine, so there doesn't appear to be any particular issue with grub. When done, I had to resync the drives (again, see the Software RAID howto) The only time I ran into trouble is that when you set up a RAID array, you have to have all the partitions installed on the machine at setup time. It seems you can't add active partitions after the fact. Other than that, in 5 cases, it's been basically perfect for me, and I plan to deploy Centos 4.x/Software RAID/Boot-root again sometime next month. Hope this helps, =) -Ben On Thursday 20 October 2005 07:59, Steve Bergman wrote:> Hi, > > I have a client that insists on going with software rather than hardware > raid1 to save a few dollars. > > Can Centos 4.2 do Boot and Root on software Raid1? > > I've heard criticisms of Grub and bootable RAID. Also, if it is not set > up to work out of the box, I'd like to try to talk them out of it. > > I've been down that road before. If I go nonstandard, by the time I > actually need to boot from the second drive in an emergency, I've > forgotten the special procedure. > > (Why can't businesses just spend a few extra dollars to do things right?!) > > Thanks for any info. > > -Steve > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >-- "The best way to predict the future is to invent it." - XEROX PARC slogan, circa 1978