Keep in mind that I'm not a certified Linux engineer. :P The only file I/O problem I know of, with 2.4 kernels, is the buffering issue. All kernel block devices are buffered by the kernel, unless they are bound by a raw device binding. This could be the culprit in the driver's bottleneck situation. Try binding a partition to raw, on that disk array, and then perform some high-speed read/write tests. You might be surprised at the throughput difference. "raw -qa" lists all bound block devices. I don't recommend raw bindings to be done when neither the hardware, nor the software writing to disk handles I/O buffering. You may end up making it worse. In my case, I have a fast caching RAID controller and D3 has a write buffering system in place. When the kernel jumps in and buffers too, things go wacko and user response drops to between 15 seconds and 1 minute under "normal" disk activity. That's for 25 users on an AMD 2+Ghz with 1GB ECC. I don't know if UV/Linux caches its own writes and reads. If it does, then using raw bindings should help with disk throughput by eliminating the middleman. Don't hold me to that, though.
PS: Changing the kernel file-max will only increase the number of files that can be open at a time. If you have a well trained disk subsystem then it's kosher to do that, because the kernel probably won't have to use swap for buffering. Mine happens to be 104851 and it's been chugging along for a couple years now with no disk I/O problems. When you pound on swap ontop of a continuous heavy I/O load, then you're just begging for a kernel panic. According to the Linux configuration guide, you should set file-max to 256 files per 4MB of memory. 1GB would be (250 * 4MB) * 256 files = 64000 for file-max. Of course, you can tweak that number up until you hit a swap or disk subsystem threshold. Your box should only use a small amount of swap under normal operating conditions. If it is using over 25%, then it's time for more memory! Glen > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Anthony > Dzikiewicz > Sent: Friday, April 29, 2005 3:58 PM > To: u2-users@listserver.u2ug.org > Subject: RE: [U2] UV on Linux > > > We have been live since October. Everything is fine at the Universe > level. We havent had any major issues at all. > One thing we used to do to get users off at the end of the night or when > needed is to do a 'MASTER OFF ALL'. It doesn't work on the Linux > version. Other than that, Universe is peachy. > > I find that support for Linux is generally lacking. Red Hat support is > 'alright'. We have RedHat support thru IBM, which is much better than > the RedHat support (IBM is usually a knowledgeable person that speaks > English very well vs the RedHat guy who is not always very knowledgeable > and has an accent that requires a special hearing device to interpret). > IBM support is cheaper too. We keep RedHat for the up2date > functionality and the resources they have. It really is a nice way to > keep things current. > > Are you using all Dell Hardware ? > > We are running an IBM xSeries Server and an EMC Clariion. We are having > performance issues with intensive writes to the disk array. There is a > minor issue with this when doing the same kind of operation on the > internal disks. Intensive disk writes could be an batch application > that reads records from one file, deletes and writes to another (say > 100,000 records type 30 files with indexes). We do this for archiving > data. It could be a linux 'cp' command copying a large file (100meg) to > the disk array. What happens is that the system goes into an iowait > state and user response is non-existent. Sometimes, the system will > hang for close to a minute until the i/o completes. We are also using > Qlogic 2340 HBA's to connect the IBM to the Clariion. If you look thru > the RedHat Bugzilla, there have been issues with the driver for this > hardware. We will be testing out some Emulex cards next week to see if > that improves things. > > If you have the luxury to evaluate your system, definitely try copying > some large files or 'archiving' type processes while users are on. > Monitor performance with the 'top' command. Then determine if things > are acceptable. > > We converted from a DG/UX box with a Clariion. Performance was never > really an issue on that platform and these types of operations would > absolutely go unnoticed. > > EMC has been trying to help with the issue since February. I have to > say that their support SUCKS !!! It seems that there is no one there > that knows anything about Linux. I am finding this in general. When > you mention that you are running Linux, a dark cloud appears. So, you > probably will not get the excellent type of support that you might be > accustomed to with Solaris. > > I would assume that you like Dell support ? My experience with them is > that they went from once upon a time very good (8 years ago or so) to > the pits. Every time I call, I get transferred overseas to India and > the conversation is almost unbearable. Recently, I ordered an extra cpu > for our testmachine, which is a Dell. They cancelled it with out any > notice ! When I called to reorder, they said I couldn't, because it > wasn't in stock. So, I have to keep calling until I get a 'hit'. This > is really a joke. Luckily, our var deals with Dell and was able to get > parts. > > If you would like to know more about the performance issue, email me > directly and I will share whatever information I have. > > > Anthony Dzikiewicz > IT Manager > Alperts Furniture > > > ---Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jerry Banker > Sent: Friday, April 29, 2005 2:49 PM > To: u2-users@listserver.u2ug.org > Subject: [U2] UV on Linux > > > We are finally moving our UV off our Sun Solaris 8 System and moving to > Redhat on a Dell system. Many of you have been on Linux for awhile so > tell me, how was your conversion? Did you have to tweak any > configuration parameters? Any pitfalls we should know about? We usually > run around 100 user sessions. > > Jerry Banker > ------- > u2-users mailing list > u2-users@listserver.u2ug.org > To unsubscribe please visit http://listserver.u2ug.org/ > ------- > u2-users mailing list > u2-users@listserver.u2ug.org > To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list u2-users@listserver.u2ug.org To unsubscribe please visit http://listserver.u2ug.org/
