Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi, in an environment of - raid - LVM on raid - DRBD on LVM - xen guest on DRBD the space of the device needs to be cleaned (overwritten by zeroes or random) before deletion of the logical volume. The usual steps would be # drbdadm down drbd6_2 # shred -n0 -zv /dev/vg1/lv_drbd6_2 # lvremove /dev/vg1/lv_drbd6_2 This works nice for small devices (up to 10 GB): # time shred -n0 -zv /dev/vg1/lv_drbd6_1 shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)... shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...800MiB/10GiB 7% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...1.9GiB/10GiB 19% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...2.9GiB/10GiB 29% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...3.8GiB/10GiB 38% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...4.9GiB/10GiB 49% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...5.9GiB/10GiB 59% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...7.0GiB/10GiB 70% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...8.1GiB/10GiB 81% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...9.2GiB/10GiB 92% shred: /dev/vg1/lv_drbd6_1: pass 1/1 (000000)...10GiB/10GiB 100% real 0m48.919s user 0m0.544s sys 0m11.917s But for larger ones e.g. 100 GB it blocks the IO on the XEN-node, triggering alerts in the monitoring of other running XEN-guests. As far as I googled ionice would not work. What I found as solution is piping through pv: # time dd if=/dev/zero | pv -L 100M | dd of=/dev/vg1/lv_drbd7_2 dd: writing to `/dev/vg1/lv_drbd7_2': No space left on device ] 2GB 0:01:32 [22.1MB/s] [ <=> ] 4194305+0 records in 4194304+0 records out 2147483648 bytes (2.1 GB) copied, 92.9986 s, 23.1 MB/s real 1m33.005s user 0m7.532s sys 0m52.443s Is there a better way? TIA Helmut Wollmersdorfer