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SGI Linux

2000-09-26 14:22:06+00 by ebradway 2 comments

I'm in the process of building our second production database server. The machine itself is a monster HP 6000r with six (6) 550Mhz Xeon CPUs, 1.25GB RAM and about 50GB+ of RAID5 diskspace. This is pretty close to the biggest PC money can buy. The Sybase license fees for the box will exceed $200K... Anyhow, being a production machine that needs to do one thing REALLY well, I am trying to take route of using readily available open source components and reconfiguring them to do what we need. To that end, I am using Red Hat 6.2 (with hand-selected packages) as my base. Sybase is pretty limited in the flavors of Linux it supports. Both Sybase and HP are quite comfortable with a Red Hat base... To that I've added the Bastille-Linux scripts - a definite must for a machine that is plugged strait into the internet by multiple OC3s. And now I'm trying to get the SGI ProPack 1.3 working the way I want. My problem is that Linux, with the 2.2 Kernel, doesn't like files bigger than 2GB. It also wants everything to write to disk via a file system. This means that Sybase has to use 2GB max files to store the data from the database. Larger databases need to be spread across multiple files. On other, more database friendly platforms, the OS supports "RAW disk IO" - letting applications write directly to unformatted partitions on the hard drive without a file system (and it's limitations) getting in the way. In order to get Linux to support this (at least the way Sybase wants it) is to install a couple kernel patches and rebuild. Those patches just happen to come with the SGI ProPack (along with a couple other goodies for high-performance database applications). So here I sit, waiting for my upteenth recompile of the kernel... Writing lots of posts to Flutterby. Letting the world know that people are really trying to use Linux for big, real-life applications. I know it might look like I'm having problems - but to achieve the same goal with HP/UX, Solaris (or may the deities continue to shine on me), Windows NT, would be considerably more difficult - or more likely - impossible. Granted I wouldn't be fighting these exact problems with another platform - here I at least have the weapons to fight well.

[ related topics: Free Software Microsoft ]

comments in ascending chronological order (reverse):

#Comment made: 2002-02-21 05:30:20+00 by: scm

I'm pretty sure there's a kernel patch out there somewhere to extend the file size limit past 2GB. It may be from SGI as well. Sorry I don't have a link...

#Comment made: 2002-02-21 05:30:21+00 by: ebradway

The problems with the file size limit extend beyond the kernel. The only way around it is to use a 64-bit file system, which I don't think Sybase supports on Linux. The issue with the file system (and it's the same with memory!) is that functions like fseek() return a signed long, which has a range of -2billion to +2billion (and change). This means any code that uses a 32-bit file system and 32-bit C STDIO library will be limited to 2GB of file space (per file) and 2GB of RAM. RAM access has been kludged to support 4GB of RAM because you rarely ever need to deal with negative numbers with RAM. Files are different, however.