[DRBD-user] A Tale of Two Identical Servers, but DRBD Only Supports Trim on One of Them

Eric Robinson eric.robinson at psmnv.com
Fri Jul 14 21:21:02 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


I have two identical Dell PowerEdge R610 servers:

Disks: 6 x Samsung SSD 840 Pro 512GB
Controller: LSI-9207-8i, same firmware
OS: SLES 12 SP2, kernel 4.4.59-92.24
DRBD: 9.0.6+git.08cda19-57.1.x86_64
Backing Device: mdraid 5, /dev/md2
Config file: /sys/module/raid456/parameters/devices_handle_discard_safely=Y
Config file: /etc/lvm/lvm.conf contains: issue_discards = 0
Config file: /etc/crypttab is not used

However, one server shows DRBD supporting TRIM...

NAME        DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO
sda                0      512B       4G         1
├─sda1             0      512B       4G         1
│ └─md0            0      128K     256M         0
├─sda2             0      512B       4G         1
│ └─md1            0      128K     256M         0
├─sda3             0      512B       4G         1
├─sda4             0      512B       4G         1
├─sda5             0      512B       4G         1
│ └─md2            0      128K     256M         0
│   └─drbd0        0      128K     128M         0
<snip>

...but the other does not, even though the underlying devices do (note the 0 values for DISC-GRAN and DISC-MAX for drbd)...

NAME        DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO
sda                0      512B       4G         1
├─sda1             0      512B       4G         1
│ └─md0            0      128K     256M         0
├─sda2             0      512B       4G         1
│ └─md1            0      128K     256M         0
├─sda3             0      512B       4G         1
├─sda4             0      512B       4G         1
├─sda5             0      512B       4G         1
│ └─md2            0      128K     256M         0
│   └─drbd0        0        0B       0B         0
<snip>

What am I missing?

--
Eric Robinson

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