> Have a FAQ which describes how to boot nodes diskless? PXE basically means "DHCP then TFTP". what you get via TFTP is much like booting from disk: first you get a bootsector (pxelinux), which then fetches a config file (again, via TFTP), which tells it how to boot. that may be to boot from the HD, but usually means to fetch yet another file or two via TFTP (kernel and initrd). IIRC, the pxelinux jumps to the kernel, which uses the initrd as its initial disk image. you can stay in the initrd, or you can a more full-fleged root, such as over NFS. or even boot directly into an NFS root with no initrd. there are somewhat tricky bits in figuring out which subtrees can stay in a tmpfs/ramdisk, and which can be NFS mounted, and how you assemble the whole into the sort of tree that normal tools are looking for. (you don't need a per-node NFS export, necessarily.)
but there's no clear right or wrong. there are also a lot of modern linux/filesystem developments that might be useful. I find tmpfs a lot nicer than ramdisks, for instance. and I like read-only NFS mounts, with attribute cache times tweaked up a bit. you have to ignore most of the "conventional wisdom" about how terrible NFS is in a cluster - it's not great, especially for large systems (hundreds of nodes). but for smallish systems, it's fine (I have a 100-node NFS-root cluster which works great). I'd advocate scaling by replicating NFS servers (why not one per rack?), rather than immediately jumping to disk-ful configurations. > That's too expensive however and eating unnecessary power. disks do not dissipate much, especially compared to other components. > 14 disks is $$$ but more importantly also eat effectively nearly 30 watt a > disk from the power current *ata disks peak at under 15W, and that's if you're 100% seek/write. in a typical cluster I'd expect to average under 10W. > (maxtors are like 22 watt and that's *after* the psu lost a lot of > power!!!!). nah. or are you talking about big 15K rpm SCSI disks? besides, decent PSU's are 70-80% efficient. it's easy to blow (hah) over 100W on fans in a 1U server. that's a lot more significant... _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
