I have recently run a similar experiment measuring how fast do various disk operations run. Although I haven't attempted to compare dd with dasdfmt and the variation is high, here are the most commonly seen numbers:
dasdfmt + pvcreate : 30-40 MB/s dd : 30-80 MB/s dasdfmt + pvcreate, parallel pool of 20 workers formatting all physical disks in a large LVM group: 150-300 MB/s After reading your results I have noticed that I have never seen dasdfmt run faster than 40 MB/s while I have regularly seen dd run at 80 MB/s. Tomas -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Marcy Cortes Sent: Thursday, November 08, 2012 2:05 AM To: [email protected] Subject: Re: dasdfmt - why are you so darn slow? CA Hidro can copy one in 11 minutes. DFDSS can dump one to VTS in 6 minutes according to my z/OS guy dumping our stuff (I wouldn't think VTS would be quicker than DASD - maybe pretty similar) I haven't timed DDR but I don't think it is all that great either - certainly it is much worse the hidro. So yeah, I think both VM and Linux could be doing better here :) Marcy -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Robert J Brenneman Sent: Wednesday, November 07, 2012 4:15 PM To: [email protected] Subject: Re: [LINUX-390] dasdfmt - why are you so darn slow? Additionally - why does Linux not make better use of the I/O subsystem ? For example, a z/OS DSF copy job copying a dataset from one volume to another uses like 6% of a CPU at most, whereas Linux dd or cp uses 100% of a CPU, and doesn't go noticably faster than the DSF job. Could Linux make better use of CCWs to have the subsystem handle the copy rather than actually moving the data blocks through the main memory? -- Jay Brenneman ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
