Re: hard-disk via virtio-blk under windows (discard_granularity=0)
Andrea Bolognani <abologna(a)redhat.com>
I'd also be surprised if this only affected Windows. Wouldn't
Linux
guests likely see a similar change in how the device is presented?
I don't understand all the impact under windows. but defrag is the
obvious part. by default windows will do disk optimization weekly.
trim was fast when I was using windows 2019 with virtio-blk drivers at
that time. and you could manually do traditional defrag to the device
although it will also do unnecessary trim after defrag. But recent
windows server 2019/2022 with recent virtio-blk driver, trim was very
slow and a bigger disk like 1TB thin-device will just show "memory not
enough" when defrag(but NTFS really need defrag). I don't know
what/when changed the behavior. I found "discard_granularity" seems
the saver for both cases.
when I use linux I don't care since it won't do trim automatically. I
need to mount with options or do fstrim for the device. and there is
no need to defrag the hard-disk. Since there is no automatic part, I
don't know if this is useful or not to distinguish hdd/sdd/thin-device
under linux?