Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> Because it is a system, that can be offline while we are on work for about > 1 > hour, i don't think we will really need LVM, i am sure to be able to > re-setup partitions in this time. Another point is, that this system > doesn't > need that much of disk-space, i will only use about 1/3, so i have 2/3 of > free space for future partitioning. LVM is often cited for this exact case: ease of future partitioning and adding to volum > > For speedup i thought about making the root and data-partitions on md-raid > 0, because the DRBD will do the mirroring, if one disk fails...? IS that a > bad idea? > Are the machines active/passive? If so, you can't boot the second one while the first one is primary. So you would have two drbds, each primary/secondary, each mounted as '/' on one machine? Otherwise you're talking about a single drbd using primary/primary and a clustering filesystem for '/', and unless you're doing a big cluster, I'd say that's adding complexity. I like to keep '/' as simple as possible. Wow, I totally lied. I'm currently using 'md' to do raid10 on '/' I would make a small '/' partition on each drive, raid1 those. Make a small swap (however much you need) on each drive. raid1 those. Maybe I'm paranoid, but I believe in mirroring swap to keep a box alive. Booting from raid1 is easy. When you setup grup/lilo, be sure to 'install' on each drive and mark each partition as bootable. How much you need for '/' depends on what you need in your OS. 2GB is usually tons of speace, especially if you don't install X and GNOME/KDE (my biggest use of space on a mininmal CentOS is the locales directory). The rest of the disk can be one big partition, which you can then raid0. Then run a drbd on top of that. giving you raid01. Many people (Lars) on this list suggest that you should have local reliable storage under drbd. That's your call. > > Perhaps it doesn't make sense, because the overlaying drbd via > GB-interfaces > is so slow, that the raid 0-speedup is never used and i can take raid 1 > without any impact on speed? If you do use raid0 under drbd, reads are always local at raid0 speed, until a drive fails, then the reads and writes are remote. > > And basically, is it better to make the raid 1 via LVM instead of md-raid > to > reduce the overhead? THAN i would use only LVM without md-raid...? > I recently asked this exact question about md vs. LVM raid0 on the LVM list. I didn't get a definitive answer. If I didn't need LVM for partitioing reasons, I wouldn't use it in place of md. Because I do need logical volumes, I figure kicking md out of the stack is one less layer to manage and have go wrong.