SSD maximal performance : native sector size, partition alignment

[Insurgo]

@rustybird

It’s going to be more difficult to somehow make the “root” volume sector-size agnostic…(The “private” xvdb and “kernel” xvdd volumes seem to work fine if /etc/xen/scripts/block is patched to configure them with 4K sectors. They’re just ext4/ext3 filesystem images without a partition table.)

@rustybird Sorry I was not more specific: I meant for the root and private volumes creation: was that tested working?

So if I understand well, I could apply your patch and have volatile volume fixed. But for creating root volumes and private volumes, I would need to build ISO, or patch stage 1 and stage 2 install so that when templates are decompressed, those are fixed to create a working system to be able to compare performance properly with/without the fixes.

I was looking for next steps to get main devs attention in seeing actual performance losses/ differences in this thread.

Otherwise, people are trying to get away of LVM thin provisioning model at install as of now. Some wants ZFS,XFS/BRTFS since speed differences are quite important.

One example of that is from @Sven at https://forum.qubes-os.org/t/ext4-vs-btrfs-performance-on-qubes-os-installs as an example of that, showing gains of ~300mb/s write speed by choosing BRTFS at install vs thin provisioning default:

@Sven

So the following numbers are from a controlled environment, run on the same hardware with the same bits present. Nothing is different except the file system. I think it is justified to call the delta “significant”.

	start	write
ext4	9.35 s	466.8 MB/s
Btrfs	7.74 s	765.3 MB/s
Δ	1.61 s (21%)	298.5 MB/s (64%)

actual measurements

ext4 start = 9.09, 9.44, 9.51, 9.64, 9.37, 9.24, 9.42, 9.14, 9.42, 9.25 s
ext4 write = 383, 424, 463, 467, 501, 446, 425, 522, 521, 516 MB/s

Btrfs start = 7.70, 7.73, 7.67, 7.68, 7.71, 7.58, 7.82, 7.83, 7.82, 7.83 s
Btrfs write = 760, 768, 773, 758, 768, 765, 750, 761, 780, 770 MB/s

Maybe others can do similar measurements when reinstalling and share them in this thread. I’d be very interested to see if these performance gains are general in nature or somehow specific to my hardware. If general in nature, maybe a case should be made to the development team to adopt Btrfs as a default.

Fixing LUKS+LVM thin provisioning would be great. Otherwise LVM is blamed for performance losses as of now where other implementations are simply not suffering from the same implementation flaws that LVM thin provisioning is suffering from, per Qubes implementation of volatile, private and root volumes creation.

@Demi maybe? I think @rustybird showed where love is needed here: SSD maximal performance : native sector size, partition alignment - #30 by rustybird