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| Guest OS may limit the amount of usable vCPUs. | ||
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| VMs with more than 32 vCPU may cause major system-wide performance degradation under very specific circumstances. Use with caution. |
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Is there a resource (internal or external) where the reader could know more about that? If not, no big deal but it would be nice to have
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It's a summary of what I know regarding the current "security supported" CPU limit.
XenServer docs says (even though 64 is no longer the actual limit)
Though the limit is 64, we recommend setting the limit to 32 if your VMs might not be trustworthy or if you want to prevent a potential impact on system availability
Discussions we had internally and with XenServer conclude that this is a arbitrary limit; and that guests with many CPUs can (maliciously or not) cause denial of service through abuse of some hypervisor mecanisms (that could take at the end too much time, and block multiples physical CPUs, eventually up to livelock/watchdog violation).
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I prefer XenServer's version (that we can't copy as is) because it insists on not trustworthy VMs yielding an increased risk
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Trustworthy suggest that trusted VMs absolutely fine, but the reality is a bit different. While malicious VMs can abuse, normal guest (with many vCPUs) can also trigger similar situations (perhaps in a less extreme way).
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I didn't mean to say that only untrustworthy VMs can trigger issues. I said "increased risk".
TSnake41
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XCP-ng 8.3 doesn't support "paravirtualized mode" anymore, it doesn't make sense to keep informations related to it. e.g hardware virtualization is now mandatory (not only for Windows) and XCP-ng will refuse to install without it. Recommend the use of a IOMMU, while not always required, it's fair to recommended it, especially since some machines could require it (e.g to use more than 256 cores). Increase memory recommendation, it's not advisable to use XCP-ng with 4 GB of memory. Fix theorical CPU limit with currently used Xen limit. Add a note regarding SLAT requirement on XCP-ng 8.3+. Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
2040 GiB is quite confusing and incorrect, and is actually 2 TiB. Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Tested limit is actually the maximum limit. Xen don't allow further than that as of today. Say "guest may limit" as in practice, the guest will likely boot but with less vCPUs usable. Warn about potential performance implications of VMs with a lot of vCPUs. Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Current wording is quite confusing and suggest that operating system has a inherent NIC limit which is probably not the case (or at least, not at this limit). The reality is more likely that lack of netif support means that VM relies on emulated devices, which has some limitations (i.e we may not expose all NICs as a emulated device). Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
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Added a note regarding SLAT, due to shadow paging removal. |
| - One or more 64-bit x86 CPUs, minimum 1.5 GHz; 2 GHz or faster multicore CPUs are recommended. | ||
| - To run Windows VMs or recent Linux versions, an Intel VT or AMD-V 64-bit x86-based system with one or more CPUs is required. | ||
| - Hardware virtualization must be enabled (Intel VT-x or AMD-V). | ||
| - Since XCP-ng 8.3, CPU must support SLAT (Intel EPT or AMD RVI/NPT). |
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| - Since XCP-ng 8.3, CPU must support SLAT (Intel EPT or AMD RVI/NPT). | |
| - Since XCP-ng 8.3, CPUs must support SLAT (Intel EPT or AMD RVI/NPT). |
| Guest OS may limit the amount of usable vCPUs. | ||
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| VMs with more than 32 vCPU may cause major system-wide performance degradation under very specific circumstances. Use with caution. |
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| - **Virtual Network Interface Controllers (NICs) per VM**: Up to **7**. | ||
| Note: Some guest operating systems may have stricter limits, or you may need to install XCP-ng Guest Tools to reach this maximum. | ||
| We recommend using paravirtualized devices is recommended. Support depends on guest operating system and whether or not XCP-ng Guest Tools are installed. |
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I actually prefer the former version. What's your intent with this change?
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| ### Networking | ||
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| - **Virtual Network Interface Controllers (NICs) per VM**: Up to **7**. |
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Since the last batch of updates, we support up to 16. Let's update.
| - **Virtual Network Interface Controllers (NICs) per VM**: Up to **7**. | |
| - **Virtual Network Interface Controllers (NICs) per VM**: Up to **16**. |
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Various improvements and fixes in the requirements page.