XCP-ng 8.0.0 Beta now available!

Ultra2D

@cg You should be careful when recommending dedup on ZFS. I think (but my knowledge might be outdated) there are still at least some caveats people should be aware of.
A quick search reveals you typically need 1-5 GB of RAM per TB of storage.

cg

@Ultra2D said in XCP-ng 8.0.0 Beta now available!:

@cg You should be careful when recommending dedup on ZFS. I think (but my knowledge might be outdated) there are still at least some caveats people should be aware of.
A quick search reveals you typically need 1-5 GB of RAM per TB of storage.

As a rule of thumb I have 1 GB per TB of storage in mind and I'm not aware of any problems with Dedup or Compression on ZFS(oL).
I wouldn't touch that (and RAID beside 0/1/10) on btrfs though - that's probably why many people are interested in ZFSoL, although the licenses are somewhat tricky.

I don't have much experience with dedup on ZFS tough, I just did some tests with about 100 of storage on another system and it worked perfect - just not the result I hoped to get, but that's data-dependend.

But hey: Prove me I'm wrong. Don't forget sources/links plz. and keep the versions in mind!

Ultra2D

@cg Sure, see man zfs :

Unless necessary, deduplication should NOT be enabled on a system. See Deduplication

And continue from there. For instance:

Deduplicating data is a very resource-intensive operation. It is generally
recommended that you have at least 1.25 GiB of RAM per 1 TiB of storage when
you enable deduplication. Calculating the exact requirement depends heavily
on the type of data stored in the pool.

cg

@Ultra2D said in XCP-ng 8.0.0 Beta now available!:

@cg Sure, see man zfs :

Unless necessary, deduplication should NOT be enabled on a system. See Deduplication

I don't really see big arguments here. As I wrote: CONSIDER. I'm sure you know what that means.
If I know I'm running a bunch of similar VMs, I'm pretty perfect by throwing a bit of RAM for multiplicating the effective space of my SSD array.
It could diminish the need for an expensive vendor dedup-array.

And continue from there. For instance:

Deduplicating data is a very resource-intensive operation. It is generally
recommended that you have at least 1.25 GiB of RAM per 1 TiB of storage when
you enable deduplication. Calculating the exact requirement depends heavily
on the type of data stored in the pool.

So what's wrong with that? I said as rule of thumb I have 1 GB per TB in mind. A rule of thumb is not a law and roughly fits. Also: ZFS should always have some RAM for caching, so you need a bit anyways and RAM is pretty cheap these days.

Though XCP-ng is a server OS: Don't forget to use ECC RAM on productive systems with important data. RAM corruption is can be pretty bad for ZFS.

Ultra2D

@cg Yes, I can read, thanks. It says "heavily consider".
I honestly don't care if you run ZFS with dedup, and if it keeps on working for you that's great, but it did sound like a recommendation for running dedup without adding a big fat warning. I felt it was necessary to add that warning.

Some more info about the rule of thumb:
https://github.com/zfsonlinux/zfs/issues/2829
https://news.ycombinator.com/item?id=8437921

ryao created this issue in zfsonlinux/zfs

open Warning about deduplication is not accurate #2829

cg

If it makes you sleep tighter: Heavily consider using ZFS. As consider means: See if it makes sense for you and estimate if you have data that could benefit from it.
It doesn't make sense to enable deduplication for AVC video archives etc. pp. It would just add complexity and overhead.

Consider always means: Read about it, see what it takes and if it makes sense - but it's a good thing and you could benefit from that. Not: Enable it, no matter what it takes.

I'm out for nitpicking about ZFS, the show is yours...

cg

I now tried to install XCP-ng 8.0.0 Beta on my new Ryzen test machine, with no success.

Install 7.6 from USB-stick works perfect.
Install 8.0.0 Beta neither works from USB-stick nor USB-DVD drive.
I also tested CH 8.0 from USB-stick: Same (so no specific XCP-ng problem)

Since Citrix won't give a - their support for unsupported (unpaid) servers is well known - about booting on a Ryzen PC, I report it here.
What happens is:
I can't see much on the screen when booting to "install", neither UEFI nor "normal boot".
When I boot to safe (both methods), it ends up like that:

mapping kernel into physical memory
about to get started...
Hardware Dom0 halted: halting machine

I don't get it. Everything seems good, no errors, nothing. Only reset button brings it back to life.

CPU: Ryzen 2200G
Mainboard: Asus Prime A320M A
Firmware Version: Version 4801 2019/05/10
PRIME A320M-A BIOS 4801
Update AM4 ComboPI 0.0.7.2A for next-gen processors and to improve CPU compatibility

Something must have been change between 7.6 and 8.0, that makes it "halt".

olivierlambert

Dom0 can't boot here. Likely related to a more recent kernel than in 7.6.

Note that I don't have any issue on a Ryzen 7 (2xxx) nor EPYC.

Anyone else with a 2200G?

cg

Additionally: I installed XS 7.6 before and 'upgraded' it via USB-stick to XCP-ng 7.6.
Worked without any problems and VMs were fine.

Also regarding boot: I had a problem like that with OPSI, as their bootimage had some changes to the kernel, that made it stop.

What helped was to limit the memory to 2G (2048M). I don't know if/how to add that to the USB-stick, to test if that helps here, too.
(Tried noapic/noacpi on OPSI before... maxmem helped!)

olivierlambert

In UEFI, you can edit the Grub menu before starting install. Try to change RAM value there

cg

I've taken a loot at the USB-stick and found grub config files. What I found was a maxmem of 8192 MB already configured.
I changed it to 2048M (I don't see any reason why the setup should need more than a few hundret MBs) aaaand it worked.
As it affected 2 different systems (opsi bootimage for PXE install and CH/XCP) I'm very sure it's a kernel bug!
Though I can't say which kernels are affected, except that old kernels work.
When I have time, I may test it on our Epyc server, but I guess that it
s more about the embedded Vega GPU and the shared memory.

https://forum.opsi.org/viewtopic.php?f=8&t=10611 Et al.
I'm not the first one, having trouble with Ryzen/Vega APU and the Linux kernel.

tl;dr:
As a workaround, I recommend setting the mem-limit for install stick generally to 2048M, as there shouldn't be any benefit for more anyways and it pushes compatibility.

Yet have to upgrade the system and see if XCP-ng 8 Beta boots properly (had it still on CH 8.0 for test).

olivierlambert

Indeed, I suppose it's related to Ryzen+Vega APU, because I can't reproduce on EPYC nor Ryzen without APUs.

Regarding making the chance upstream, I'm not entirely confident to make the modification, because it's hard to evaluate the impact (our RC is pretty close now). But it's up to @stormi to decide

stormi

At this stage, I'd rather document the issue to help people workaround it than change the default values inherited from Citrix (who tested the installer on a lot of hardware). I also suggest to open an issue at https://github.com/xcp-ng/xcp/issues so that other users that would meet the same issue could share their experience and let us try to estimate whether it's a widely spread issue or something very specific to some hardware.

olivierlambert

Looks like the best way to me

cg

@cg said in XCP-ng 8.0.0 Beta now available!:

https://forum.opsi.org/viewtopic.php?f=8&t=10611 Et al.

I created an issue, IMHO it would be good if the problem itself makes it to upstream to either bump someone to fix it or get feedback that problem is known/fixed in version X.Y.Z.

For reference:
https://github.com/xcp-ng/xcp/issues/206

nagilum99 created this issue in xcp-ng/xcp

closed Unable to boot installer with AMD Ryzen APUs #206

stormi

@cg said in XCP-ng 8.0.0 Beta now available!:

I created an issue, IMHO it would be good if the problem itself makes it to upstream to either bump someone to fix it or get feedback that problem is known/fixed in version X.Y.Z.

Thanks for creating the issue.

You could test with Citrix Hypervisor and then report it at https://bugs.xenserver.org
Maybe they'll want to investigate even if the hardware is not officially supported. If someone can reproduce the issue on supported hardware, that would make things easier.

cg

@stormi said in XCP-ng 8.0.0 Beta now available!:

You could test with Citrix Hypervisor and then report it at https://bugs.xenserver.org
Maybe they'll want to investigate even if the hardware is not officially supported. If someone can reproduce the issue on supported hardware, that would make things easier.

Though I doubt it was woth the effort, as the support over there is well known (especially for not supported configurations etc.) I did it - for the reason of trying to improve stuff (and giving back to OSS community):
https://bugs.xenserver.org/projects/XSO/issues/XSO-955

cg

I just did the upgrade from 7.6 to 8.0.0 beta via USB-stick (with workaround): I successfully upgraded the existing installation including the softwareraid on the first 2 SSDs.

# cat /proc/mdstat 
Personalities : [raid1] 
md127 : active raid1 sda[0] sdb[1]
      117220736 blocks super 1.0 [2/2] [UU]
      bitmap: 1/1 pages [4KB], 65536KB chunk

Everythings fine, even RAID survived. ZFS stuff will come later. Would be good if that would find a way into XCP-ng Center (is it in XOA yet?) for easier management. Likewise for Ext4.

olivierlambert

Find a way to what?

cg

New SR -> Type -> ZFS... creatig a new SR via GUI/XCP-ng Center.