Hello Martin, Thank you for the response. My understanding is that offset= can cause testing to begin at a particular offset in a file, but I believe the region of the file that will be used for the tests are between "offset" and "offset+size." I want to know how to perform X bytes of random I/O between offset 0 and the end of the file, where X is not the size of the file. On Sat, Oct 6, 2012 at 3:18 AM, Martin Steigerwald <Martin@xxxxxxxxxxxx> wrote: > > Am Montag, 1. Oktober 2012 schrieb Matt Hayward: > > Hello, > > Hi Matt, > > > I frequently want to perform a set amount (e.g. 1 GB) of random I/O > > over very large files or devices (e.g. 1 TB). > > > > I have noticed that when using the "size" argument to control the > > amount of I/O, it also has the side effect of constraining the I/O to > > the first "size" bytes of the file. > > > > Is there a way to tell FIO to perform X bytes of random I/O on a > > file of size Y and have the random I/O distributed throughout the > > extent of Y where Y > X? > > How about > > offset=int > Offset in the file to start I/O. Data before the offset will > not be touched. > > offset_increment=int > If this is provided, then the real offset becomes the offset > + offset_increment * thread_number, where the thread number > is a counter that starts at 0 and is incremented for each > job. This option is useful if there are several jobs which > are intended to operate on a file in parallel in disjoint > segments, with even spacing between the starting points. > > Thanks, > -- > Martin 'Helios' Steigerwald - http://www.Lichtvoll.de > GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- Matthew Hayward Director Professional Services Delphix M: 206.849.6389 275 Middlefield Road, Suite 50 Menlo Park, CA 94025 http://www.delphix.com -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
