[ClusterLabs] One volume is trimmable but the other is not?

[Klaus Wenninger]

On 01/25/2018 11:45 PM, Eric Robinson wrote:
>
> I sent this to the drbd list too, but it’s possible that someone here
> may know.
>
>  
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> This is a WEIRD one.
>
>  
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> Why would one drbd volume be trimmable and the other one not?
>

iirc drbd stores some of the config in the meta-data as well -
like e.g. some block-size I remember in particular - and that
doesn't just depend on the content of the current config-files
but as well on the history (like already connected and to
whom).
Don't know if that helps in particular - just saying taking a
look at differences on the replication-partners might be
worth while.

I know that it shows the maximum discard block-size 0 on
one of the drbds but that might be a configuration passed
down by the lvm layer as well. (provisioning_mode?)
So searching for differences in the volume-groups or
volumes might make sense as well.

Regards,
Klaus

>  
>
> Here you can see me issuing the trim command against two different
> filesystems. It works on one but fails on the other.
>
>  
>
> ha11a:~ # fstrim -v /ha01_mysql
>
> /ha01_mysql: 0 B (0 bytes) trimmed
>
>  
>
> ha11a:~ # fstrim -v /ha02_mysql
>
> fstrim: /ha02_mysql: the discard operation is not supported
>
>  
>
> Both filesystems are on the same server, two different drbd devices on
> two different mdraid arrays, but the same underlying physical drives.
>
>  
>
> Yet it can be seen that discard is enabled on drbd0 but not on drbd1…
>
>  
>
> 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        1M     256M         0
>
> │   └─drbd0                            0        1M     128M         0
>
> │     └─vg_on_drbd0-lv_on_drbd0   393216        1M     128M         0
>
> └─sda6                                 0      512B       4G         1
>
>   └─md3                                0        1M     256M         0
>
>     └─drbd1                            0        0B       0B         0
>
>       └─vg_on_drbd1-lv_on_drbd1        0        0B       0B         0
>
>  
>
>  
>
> The filesystems are set up the same. (Note that I do not want
> automatic discard so that option is not enabled on either filesystem,
> but the problem is not the filesystem, since that relies on drbd, and
> you can see from lsblk that the drbd volume is the problem.)
>
>  
>
> ha11a:~ # mount|grep drbd
>
> /dev/mapper/vg_on_drbd1-lv_on_drbd1 on /ha02_mysql type ext4
> (rw,relatime,stripe=160,data=ordered)
>
> /dev/mapper/vg_on_drbd0-lv_on_drbd0 on /ha01_mysql type ext4
> (rw,relatime,stripe=160,data=ordered)
>
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