[DRBD-user] DRBD Trim Support

[Lars Ellenberg]

On Sat, Jan 08, 2022 at 04:24:54AM +0000, Eric Robinson wrote:
> According to the documentation, SSD TRIM/Discard support has been in DRBD
> since version 8. DRBD is supposed to detect if the underlying storage
> supports trim and, if so, automatically enable it. However, I am unable to
> TRIM my DRBD volumes.
> 
> [root at ha50a mysqld]# fstrim /ha
> fstrim: /ha: the discard operation is not supported
> 
> It looks like DRBD disk is the only thing in the stack that does not have trim enabled...

I would expect that you will find a log line like
discard_zeroes_data=0 and discard_zeroes_if_aligned=no: disabling discards

So you need to tell DRBD that you know that your storage backend
reliably returns _zeros_ for unmapped blocks, by setting
	discard-zeroes-if-aligned yes;
(and hope that is in fact the case)

    Lars