On Thu, Aug 18, 2011 at 10:13 AM, Jonathan Barber <jonathan.barber@xxxxxxxxx> wrote: > > On 13 August 2011 04:24, Paras pradhan <pradhanparas@xxxxxxxxx> wrote: > > Alan, > > Its a FC SAN. > > Here is multipath -v2 -ll output and looks good . > > -- > > mpath13 (360060e8004770d000000770d000003e9) dm-28 HITACHI,OPEN-V*4 > > [size=2.0T][features=1 queue_if_no_path][hwhandler=0][rw] > > \_ round-robin 0 [prio=2][active] > > \_ 5:0:1:7 sdt 65:48 [active][ready] > > \_ 6:0:1:7 sdu 65:64 [active][ready] > > --- > > > > If I don't make an entire LUN a PV, I think I would then need partitions. Am > > i right? and you think this will reduce the speed penalty? > > The (possible) speed penalty with a partition + LVM is because the > blocks in the LVM/filesystem aren't aligned with the blocks in the > storage system. So when you write a block in the the OS, the storage > system has to write to two blocks. You can overcome this by manually > aligning the partitions with the underlying storage. > > You can also just not use any partitions/LVM and write the filesystem > directly to the block device... But I'd just stick with using LVM. > Here is what I have noticed though I should have done few more tests. iozone o/p with partitions (test size is 100MB) - "Output is in Kbytes/sec" " Initial write " 265074.94 " Rewrite " 909962.61 " Read " 1872247.78 " Re-read " 1905471.81 " Reverse Read " 1316265.03 " Stride read " 1448626.44 " Random read " 1119532.25 " Mixed workload " 922532.31 " Random write " 749795.80 -- without partitions: "Output is in Kbytes/sec" " Initial write " 376417.97 " Rewrite " 870409.73 " Read " 1953878.50 " Re-read " 1984553.84 " Reverse Read " 1353943.00 " Stride read " 1469878.76 " Random read " 1432870.66 " Mixed workload " 1328300.78 " Random write " 790309.01 --- > > If you want to create a LV that uses all of the space on a VG, you can use: > # lvcreate -l 100%FREEVG -n $NAME $VGNAME > > Do you see the same problem if you create the LV without CLVMD > running? This thread suggests it's possible to stop clvmd whilst the > cluster is running: > https://www.redhat.com/archives/linux-cluster/2008-November/msg00151.html > > If you run "lvcreate -ddddddd -vvv ..." do you see any useful messages? I got this locking problem resolved after rebooting all the nodes . What I have noticed is after adding a LUN, under /dev/mpath instead of wwid i was seeing as: lrwxrwxrwx 1 root root 8 Aug 9 17:30 mpath13 -> ../dm-28 After reboot lrwxrwxrwx 1 root root 7 Aug 15 17:53 360060e8004770d000000770d000003e9 -> ../dm-9 So whats is going not I am not sure. Looks like the issue with automatic dmsetup? Thanks Paras. > > Cheers > > > Thanks > > Paras. > > > > > > On Fri, Aug 12, 2011 at 8:39 PM, Alan Brown <ajb2@xxxxxxxxxxxxxx> wrote: > >> > >> On 12/08/2011 17:24, Paras pradhan wrote: > >>> > >>> Does it mean that I don't need mpath0p1 ? If its the case i don't need to > >>> run kpartx on mpath0? > >> > >> You still need kpartx, but that's a bit clunky anyway. Let dm-multipath > >> take care of all that for you. > >> > >> (The last time I used kpartx and friends was 2003. Dm-multipath and > >> multipathd are much more user-friendly. All you need then is multipath -v2 > >> -ll to verify things are where they should be...) > >> > >>> And not having mpath0p1 will take away this device mapper ioctl failed > >>> issue when creating lvcreate? > >>> > >> > >> I think that's a separate issue. What's the underlaying structure? SAN? > >> FC? iscsi? drdb? > >> > >>> I am really confused why this lock has failed , also not sure if this is > >>> related to this >2TB LUN. > >>> > >> > >> It's not. Some of my LUNs are 25+Tb > >> > > > > > > > >> > >> FWIW having PVs on LUN partitions introduces a small but measurable speed > >> penalty over making the entire LUN a PV - this is mostly down to the small > >> offset a partition table adds to the front of the LUN. > >> > > > > > > > > > > > > -- > > Linux-cluster mailing list > > Linux-cluster@xxxxxxxxxx > > https://www.redhat.com/mailman/listinfo/linux-cluster > > > > > > -- > Jonathan Barber <jonathan.barber@xxxxxxxxx> > > -- > Linux-cluster mailing list > Linux-cluster@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/linux-cluster -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
