On Sat, 2004-10-23 at 18:52, Guy wrote: > You said: > "will raid by default choose different chunk size if device size is > different, for example, sda is 400GB while sda1 is 50GB?" > > No, but the random seek test will give different results. 50GB will perform > better, since less head travel. > > Why the difference? I would want everything the same for both tests. > so assume raid use same chunk size for both 50GB partition and 400GB disk, i can not understand why here a near half performance down grade. > Guy > > -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx > [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Ming Zhang > Sent: Saturday, October 23, 2004 6:39 PM > To: Guy > Cc: linux-raid@xxxxxxxxxxxxxxx > Subject: RE: md on partition > > On Sat, 2004-10-23 at 12:12, Guy wrote: > > I guess Neil was wrong, or I misunderstood something. > > Were both test with the same RAID and LVM config? Or was 1 RAID0 and the > > other RAID5? > yes, if i tested RAID0, then will use RAID0 for both partition or whole > disk scenarios. > > > > > If RAID5, are you sure the resync was done before you did your tests? > > "cat /proc/mdstat" to determine this. > > > need to recheck. :) > > > Yes, size does matter! Chunk size that is. Not sure about extent size. > > > will raid by default choose different chunk size if device size is > different, for example, sda is 400GB while sda1 is 50GB? > > > As long as the only difference was the whole disk vs partitions, then > > partitions make a big difference! This sucks! > > > > Guy > > > > -----Original Message----- > > From: linux-raid-owner@xxxxxxxxxxxxxxx > > [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Ming Zhang > > Sent: Saturday, October 23, 2004 11:52 AM > > To: Guy > > Cc: linux-raid@xxxxxxxxxxxxxxx > > Subject: RE: md on partition > > > > thx but i met this problem. > > > > i use 4 x 400GB SATA disks, i make a raid 0 or 5, and build a vg on top > > of md, then use bonnie++ to test read performance. > > > > LVM (MD = sda+sdb+..) = 95MBsec, md is built on top of whole disk. > > > > LVM (MD = sda1+sdb1+.) = 48MBsec, md is built on top of each partition. > > > > so where is the problem? does md chunk size matter? or lvm extent size > > matters? thx. > > > > > > ming > > > > On Sat, 2004-10-23 at 02:07, Guy wrote: > > > I found this old message: > > > "On Tuesday June 1, maheshext3@xxxxxxxxx wrote: > > > > > > > > --- Neil Brown <neilb@xxxxxxxxxxxxxxx> wrote: > > > > > > > > > > What does > > > > > ls -l /dev/hd[eg]5 > > > > > show? How about > > > > > cat /proc/partitions > > > > > dd if=/dev/hde5 of=/dev/null bs=1024k > > > > > > > > Thanks a lot, Neil, turns out those nodes were not present. After I > > > > mknod'd them, all's fine in RAIDland... > > > > Quick question: does using extended partitions for RAID affect > > > > performance? > > > > > > The fact that the partitions are "extended" is invisible to most of the > > > kernel, and it could not have any affect of performance. > > > > > > NeilBrown" > > > > > > Guy > > > > > > -----Original Message----- > > > From: linux-raid-owner@xxxxxxxxxxxxxxx > > > [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Ming Zhang > > > Sent: Friday, October 22, 2004 1:28 PM > > > To: linux-raid@xxxxxxxxxxxxxxx > > > Subject: md on partition > > > > > > Hi folks. > > > > > > I remembered that there was a discussion on the list about some abnormal > > > performance penalty if u use a partition instead of a whole disk for MD. > > > But I could not find this discussion via archival or google. > > > > > > Could somebody be kindly enough to point me to the right spot? Thanks a > > > lot. > > > > > > Ming > > > > > > > > > - > > > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html -- -------------------------------------------------- | Ming Zhang, PhD. Student | Dept. of Electrical & Computer Engineering | College of Engineering | University of Rhode Island | Kingston RI. 02881 | e-mail: mingz at ele.uri.edu | Tel. (401) 874-2293 | Fax. (401) 782-6422 | http://www.ele.uri.edu/~mingz/ | http://crab.ele.uri.edu/gallery/albums.php -------------------------------------------------- - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
