On Montag 20 Oktober 2008, Conway S. Smith wrote: > On Mon, 20 Oct 2008 08:54:20 +0200 > > Wolfgang Liebich <[EMAIL PROTECTED]> wrote: > > Hi, > > > > <SNIP> > > > > > the howtos on gentoo-wiki worked well for me. > > > > I'm working with them, too. Just one question remains: I want to use > > udev. Do I have to create the md devices or does udev that for me? > > udev will do it for you. But make sure your initramfs init script > unmounts /sys & /proc.
just don't use an initramfs/initrd. > > Sorry, I'm neither a LVM nor a RAID export - could you please > > elaborate on that? > > I like LVM because of the convenience it adds. > > Write barriers are a feature to allow write caching on the hard disks > w/out endangering filesystem integrity. Write caching helps > performance significantly, but also allows the disk to re-order write > requests - the disk may actually write a write-request that was > received later before a write-request that was received earlier, > which in some situations can lead to filesystem corruption. Write > barriers are a special type of request that the disk is not allowed > to reorder around - everything the disk receives before the write > barrier must be written before anything received after the write > barrier. But in order to work, write barriers need to be supported > by every layer from the filesystem down to the actual disk; if your > filesystem is on top of LVM & LVM doesn't support write barriers, > then you won't be able to use them, and if write caching is enabled > on the actual disks, you may be risking fileystem corruption. The > Device Mapper kernel subsystem (dm-crypt, dm-raid, LVM, etc.) does > not support write barriers - but neither does MD RAID except for > RAID1, so write caching is dangerous except for filesystems directly > on disk partitions or on RAID1 (if the RAID1 is directly on disk > partitions). also, reiserfs and xfs turn barriers on by default, ext3 turns it off per default. Because of 'performance reasons'.
