On Sep 27, 2014, at 12:42 PM, Errol Neal wrote: > Hi There. Hoping to get some clarity on some performance woes in a little testing environment that I've setup. > > I am experimenting with LVM mirrors on a CentOS 6.5 cluster. > > I have two VMs running on ESX5.5 that are sharing two RDM luns from an SRP target server running SCST. > > Performance however seems to take a huge hit compared to a vanilla volume > > > [root@scst1 ~]# vgs > VG #PV #LV #SN Attr VSize VFree > hadata 2 5 0 wz--nc 999.99g 149.99g > vg_scst1 1 2 0 wz--n- 39.51g 0 > > [root@scst1 ~]# lvs -a -o +devices > LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert Devices > mirror1 hadata mwi-a-m--- 100.00g 100.00 mirror1_mimage_0(0),mirror1_mimage_1(0) > [mirror1_mimage_0] hadata iwi-aom--- 100.00g /dev/sdb1(0) > [mirror1_mimage_1] hadata iwi-aom--- 100.00g /dev/sdc1(0) > mirror2 hadata mwi-a-m--- 100.00g 100.00 mirror2_mimage_0(0),mirror2_mimage_1(0) > [mirror2_mimage_0] hadata iwi-aom--- 100.00g /dev/sdb1(25600) > [mirror2_mimage_1] hadata iwi-aom--- 100.00g /dev/sdc1(25600) > mirror3 hadata mwi-a-m--- 100.00g 100.00 mirror3_mimage_0(0),mirror3_mimage_1(0) > [mirror3_mimage_0] hadata iwi-aom--- 100.00g /dev/sdb1(51200) > [mirror3_mimage_1] hadata iwi-aom--- 100.00g /dev/sdc1(51200) > mirror4 hadata mwi-a-m--- 100.00g 100.00 mirror4_mimage_0(0),mirror4_mimage_1(0) > [mirror4_mimage_0] hadata iwi-aom--- 100.00g /dev/sdb1(76800) > [mirror4_mimage_1] hadata iwi-aom--- 100.00g /dev/sdc1(76800) > test hadata -wi-a----- 50.00g /dev/sdb1(102400) > lv_root vg_scst1 -wi-ao---- 31.65g /dev/sda2(0) > lv_swap vg_scst1 -wi-ao---- 7.86g /dev/sda2(8102) > > [root@scst1 ~]# dd if=/dev/sdb1 of=/dev/null bs=1M count=20000 > 20000+0 records in > 20000+0 records out > 20971520000 bytes (21 GB) copied, 41.0031 s, 511 MB/s > > [root@scst1 ~]# dd if=/dev/hadata/test of=/dev/null bs=1M count=20000 > 20000+0 records in > 20000+0 records out > 20971520000 bytes (21 GB) copied, 44.344 s, 473 MB/s > > [root@scst1 ~]# dd if=/dev/hadata/mirror1 of=/dev/null bs=1M count=20000 > 20000+0 records in > 20000+0 records out > 20971520000 bytes (21 GB) copied, 365.685 s, 57.3 MB/s > > > Is this just the life of a LVM mirror and the performance here is about as good as it gets? Is the performance also degraded in this way when using single machine (i.e. not cluster)? brassow _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
