On Tue, Apr 13, 2021 at 9:00 AM Wido den Hollander <wido@42on.com> wrote:
On 4/12/21 5:46 PM, Dan van der Ster wrote:
Hi all,
bdev_enable_discard has been in ceph for several major releases now but it is still off by default. Did anyone try it recently -- is it safe to use? And do you have perf numbers before and after enabling?
I have done so on SATA SSDs in a few cases and: it worked
Did I notice a real difference? Not really.
Thanks, I've enabled it on a test box and am draining data to check that it doesn't crash anything.
It's highly debated if this still makes a difference with modern flash devices. I don't think there is a real conclusion if you still need to trim/discard blocks.
Do you happen to have any more info on these debates? As you know we have seen major performance issues on hypervisors that are not running a periodic fstrim; we use similar or identical SATA ssds for HV local storage and our block.db's. If it doesn't hurt anything, why wouldn't we enable it by default? Cheers, Dan