On Mon, 2008-10-13 at 18:33 -0700, Grant Grundler wrote: > On Mon, Oct 13, 2008 at 3:19 PM, kenneth johansson <ken@xxxxxxxxx> wrote: > ... > >> Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"? > > > > I changed to use O_DIRECT and it's much more consistent now. 69-75 with > > 74 about 95% of the time. > > That's low but it could be worse. Many things can contribute to slow > disks. Well my main problem was that it was fluctuating so much that can't be right. > Favorites are overtemp (See SMART field 194) and vibration (no > measurement possible w/o special equipment). "dd" isn't exactly a > performance application until one uses really big block sizes (1MB or > larger). All my numbers comes from using 1MB blocks. but I'm not using dd. After removing the logic that actually put some data into the buffers I do get about 105 MB/sec using O_DIRECT. I'm doing a full disk write now to get a reference plot. Not using O_DIRECT should be almost identical. > > the disk is supposed to have 105 115 sustained > > data rate. > > Where did 105-115 number come from? datasheet . they listed two drives in the same column so that was not the range it was sustained OD and the model I have max out at 105. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
