So what's the problem you're trying to solve? If you simulate any database operation with OS utilities like dd you have to be sure you're simulating it the same way as database does.
For example, Oracle opens its filesystem datafiles always with O_SYNC option and with O_DIRECT dependent on whether it's parameter filesystemio_options says to use direct IO. I'm not sure about how dd behaves. It'd be best to truss both processes and make sure same options are used. If Oracle is slow doing queries then the DB people should first make sure whether their query actually uses an efficient execution plan before talking about IO. They could enable sql_trace for their queries and measure how much time these spend on waiting on IO. Tanel. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stephen Petersen Sent: 10 June 2006 09:47 To: perf-discuss@opensolaris.org Subject: [perf-discuss] Re: Re: maxphys and sd_max_xfer_size Greetings, I stumbled across this discussion and found it very interesting but I am still none the wiser to what is a better practice. I found this when googling for poor I/O with a V440 and a 3510 much the same as mentioned in this discussion. The V440 writes to the 3510 four times faster than it reads or so the database people say. To prove it, they used a similiar dd operation as discussed here but as the 3510 logical drives are setup for 32k blocks, they used 32k instead of 1024/8096k. The dd wrote to vxfs filesystems, not raw devices. Oracle is very slow when doing queries and the database people say the data in indexed and there are no joins for hell. I have not done this myself (yet) but if any of the settings discussed here are good or bad, I would love to know. I am assuming that Dave is the Ortera man and you know a bit about this. Regards Stephen This message posted from opensolaris.org _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
