I don't have any answer to your actual question, but I do have a comment on going diskless.
Depending on the type of jobs you will run, you probably get better performance if you have a disk available. First and foremost, if your users generate large simulation outputs or whatever, I always tell my users to generate them under /scratch, which is always guaranteed to be local, minimum 1.5Gb sata, and avoid the bottleneck of all machines hitting the file server across a 1Gb connection with NFS/IP overhead. Additionally, believe it or not, having swap space actually improves performance. Unless you have truly massive amounts of RAM, you can see this easily - Run "free" and if you see that all your memory is consumed (it usually is) then you would benefit by having swap space. (see below) The kernel will automatically expand itself infinitely for improved caching and buffering, it will cache every file it reads, it will buffer every file it writes. It will automatically release its own memory to make room for active processes as they request memory. Therefore when you run "free" you will normally see all memory consumed, (mostly by the kernel) but swap space generally idle. By having swap available, you give the kernel freedom to choose which is more important to keep in memory: The process that has been idle, or the file which has been buffered. The only way you can avoid this situation is to have such a massive amount of ram that the kernel can buffer/cache every file forever, while every active process gets all the ram it wants, and your machine never runs out of memory. Otherwise, you get a performance boost by allowing the kernel to choose what's the least important thing to keep in memory. But the avoidance of 1Gb bottleneck to network file share is the most important reason to have a local disk. > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Scott Ehrlich > Sent: Wednesday, February 06, 2008 11:41 AM > To: [email protected] > Subject: [BBLISA] RAM for cluster net boot? > > I'm looking at building a small cluster of disk-less 1 or 2U servers > and will > probably use CentOS 5. > > Since these machines will not have any hard drives, what would be the > minimum > amount of RAM I'd need? Also, if using Rocks or something similar, > will that > help cluster the RAM together so 4 servers x 4 GB RAM each = 16 GB > available? > > Some applications might be CPU intensive, others might be RAM > intensive, so I > need to play that balance, too. > > Thanks. > > Scott > > _______________________________________________ > bblisa mailing list > [email protected] > http://www.bblisa.org/mailman/listinfo/bblisa _______________________________________________ bblisa mailing list [email protected] http://www.bblisa.org/mailman/listinfo/bblisa
