Tony Travis wrote: > Tomislav Maric wrote: >> [...] >> I've seen Centos mentioned a lot in connection to HPC, am I making a >> mistake with Ubuntu?? > > Hello, Tomislav. > > [Just let me put my flame-proof trousers on...] > > I know a lot of HPC people on this list use RH-based distros, but I use > Ubuntu for HPC and I think it's very good. In fact I started a thread on > the Ubuntu forums about EasyUbuntuClustering: > > http://ubuntuforums.org/showthread.php?t=1030849 > > I used RH6-9, and Fedora core2, but I switched to Debian and now Ubuntu. >
So it can be done. :) Great, I love Ubuntu. :) >>> You also need to be aware that RAID5 is not so good when writing to the >>> disk, because parity has to be calculated and written to the disk. In >>> fact this performance penalty has lead to a campaign against RAID5: >>> >>> http://www.baarf.com/ >> Okaay. :) There's war going on against it. > > This campaign really made me think twice about what I was doing using > RAID5. I lied to you (a bit) because I've bought more 3ware 8006-2's to > put /home on RAID10 for our Beowulf servers. I must admit that hot-swap > is one of the main reasons, but BAARF did come into it as well. > >> [...] >> Yeah, but isn't RAID1 used for disk mirroring? How then would I get any >> speedup? From what I've read so far, data stripping is where I get the >> performance boost when using RAID: there's no real parallel >> writing/seeking applied to single data stream in RAID1... > > You don't get a speedup when writing, but you avoid the performance > penalty of writing to RAID5. Writing to a RAID1 is essentially the same > speed as writing to a single disk. However, you do get a performance > benefit when reading from RAID1, and you decouple disk access between > the 'system' disk and /home on the RAID1 if you follow my suggestion. > OK, thanks, I think I'm getting the hang of this... I guess I'll have to balance some goals and play around with the configurations. > On COTS motherboards the main bottleneck is the PCI bus anyway, not the > SATA disks. Have you benchmarked the disk i/o performance that your > hardware is capable of? > I'm assembling and configuring something like this for the first time ever. So the answer is: not yet, haven't thought of that, thank you very much for the advice. :) >> [...] >> Thanks, my only problem is that I've reached my financial limits for my >> home project so I have to work with what I have. :) I'll definitely save >> this e-mail in my "importants" folder. > > I set out with similar ideas to yours, but in the end you get what you > pay for. My four-disk software RAID systems work fine and they survive > single disk failures without crashing or losing any data. However, we've > had a couple of near double disk failures so I decided to put the system > and /backups on hardware RAID1 instead. I'm still using software RAID5 > for /home, and I think this is a reasonable compromise between cost, HA > and performance. > I figured it's something like that... hardware RAID will have to wait for a while, definitely... Thanks, Tomislav > Good luck! > > Tony. _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
