You are asking the wrong questions really. Firstly, using dd in a massive sequential transfer from a pseudo device only gives you a feel for the maximum throughput rate for your system when there is nothing else happening. However, unless your application is "dd a huge sequential set of zeros from a pseudo device" then it has very little relevance to how fast the database will respond. For a start, it must traverse indexes in the file, take concurrency locks, will not always have the benefit of so much cache memory ,must compete with all your other processes and actually do something with the data once it has taken it off disk.
Secondly, your traversals are likely not sequential as the COB stuff is not designed to take advantage of such things. SO, you are probably traversing files in a sequence of sorted accesses, which is pretty much the worst thing you can do. Those bursts you see are probably when the sequence is in natural order (as all programs should do if at all possible). So, you are seeing the consequence of: a) Not the best application programming; b) The database has to do real thing, not just dd from a pseudo device; c) Comparing sequential transfer (with cache) to random access; d) A likelihood that you have not got perfectly sized files; e) A likelihood that the files are not sequential on disk; f) A likelihood that you should defragment your file system; You can make your files more efficient by resizing them (though jrf now does a poor job on some instances), then using dd and a large block size to move them, then rename them, such that the file is definitely sequential on disk (CREATE-FILE does a good job, but then you add data and it can get fragmented). You also don't state what file types you are using, but it seems you pay a high price for the auto-resizing files. Finally, use as many physical disks as you can and note that as the disk numbers increase, RAID 5 is usually better performing than RAID 10 with jBASE on AIX local disk arrays (don't use SAN). Jim > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of aft3rgl0w > Sent: Wednesday, August 25, 2010 6:59 AM > To: jBASE > Subject: jbase 4 performance (speeds...?) > > Hello all. > > i would like to see what sort of speeds do you get generally get on a system > running jbase. more specifically, we have a power 5 570 machine that runs > AIX 5.3 TL 11 SP4 and we are running jbase 4.1.5.29 on top of that. > the machine 8 CPUs at 1900Mhz and 16GB of memory. thats our production > environment and its attached on a IBM DS4800 storage. our jbase and > production environment are on the same filesystem that resides on 4 > physical disks of the storage which are on RAID 10. a dd if=/dev/zero > of=testfile0 bs=4096 count=1000000 gives me speeds of around and more > than 110MB/sec. > now running from jsh several SELECT statements or COUNT etc and looking > through the topas utility but also nmon, the average read disk speeds will > never go beyond 7-8MB/sec. rarely i will notice bursts of 20MB/sec but > usually it runs around 5MB/sec or even less.I understand that theres also > logical processing that needs to be done from the CPU so its not only disks, > but still i feel that 7-8MB/sec is too slow since the system is capable of a lot > more.running nmon to collect date throughout the duration of a COB i get > average read speed of about 1 MB/sec and a max of 74MB/sec. that > 74MB/sec sounds very good but its probably at a burst time period and lasted > for less than a blink of they eye. Write speeds arent any much different > either.all the speeds i mentioned are noticed while im the only user logged > on the server. > it would be nice to know what sort of speeds you are running on and if im the > only one running so slow. > Thanks. > > > > > -- > Please read the posting guidelines at: > http://groups.google.com/group/jBASE/web/Posting%20Guidelines > > IMPORTANT: Type T24: at the start of the subject line for questions specific > to Globus/T24 > > To post, send email to [email protected] To unsubscribe, send email > to [email protected] > For more options, visit this group at > http://groups.google.com/group/jBASE?hl=en -- Please read the posting guidelines at: http://groups.google.com/group/jBASE/web/Posting%20Guidelines IMPORTANT: Type T24: at the start of the subject line for questions specific to Globus/T24 To post, send email to [email protected] To unsubscribe, send email to [email protected] For more options, visit this group at http://groups.google.com/group/jBASE?hl=en
