Posts made by flomer

Well, it's on our lab network, and I am playing with and learning XenServer at the moment. I might move some of our production servers from vSphere to XenServer if things work out nicely.

OK, I guess I could try and test it if I have the time soon

Hm. So you are saying that a VM that is mirgated form the 1,9 GHz host to the 3,1 GHz host will actually run faster, even though it will not report the correct speed until a reboot? In that case it will be perfectly fine to pool the hosts together, for added flexibility and possible HA-fun

Well, I am just trying to make use of some old hardware here, and buying identical new(old) machines is out of the question.

But, if this means that the faster machine will have to be masked to a lower CPU speed in order to allow for VMs to be live migrated from one to the other in the pool, this means I will better utilize the machines if they are separate, and not pooled. Right?

I will instead have to use some other machines for the VMs that I would like to experiment with HA for. I have three other Intel-based older machines that have identical CPUs, so for this pool this will not be an issue.

OK. I just started the VM on the host with 1,9 GHz CPUs. When I run 'cat /proc/cpuinfo' it tells me that the "cpu MHz : 1908.811". Then I migrate the VM to the other host (with physical CPU of 3,1 GHz). The two hosts are not now in the same pool. When I run the same command after the migration it tells me that the CPU is still 1,9 GHz. The VM now has a vCPU of speed 1,9 GHz but is really running on a server with CPUs at 3,1 GHz. Hence my question...
I try to reboot the VM and after the reboot the above command gives me the more expected result of "cpu MHz : 3100.172". This seems logical and I can live with this CPU "masking" when migrating a VM from one host to another on an irregular basis.
Now, I am wondering if this means that if the two hosts are put in a pool if the faster host never really will live up to its full potential, due to this "masking" of CPU speeds? Will the faster CPU always be masked as slower, in order to be more like the slower in features? If so, it seems I will lose a lot of computing power when I gain the benefits of a pool... Am I still unclear?

Well, the one is at 1,9 GHz and the other is 3,1 GHz.

What I mean is, what happens when a VM is live migrated from the 1,9 to the 3,1 host -- what happens to the virtual CPU speed? And what about the other direction? Will a reboot of the VM restore the vCPU speed to local host speed, or what...?

Will the faster of the two hosts in effect have its CPU speed lowered for all VMs in order to look like a heterogenous pool?

Yes, I know they are power hungry, but my department doesn't have to worry about the bill -- it's handled by the higher levels in the organization.

Perhaps I phrased the question in a clumsy way since I get no answer... What happens to the virtual CPU of a VM that is migrated from one server to the other? Will the virtual CPU change speed after the VM is rebooted on the new server?

Dear community!
I have two old AMD servers, one with 8 Quad-Core AMD Opteron 8347 @ 1908 MHz and 64 GB RAM and the other one with 4 Quad-Core Opteron 8393 SE @ 3100 MHz and 32 GB RAM. I managed to add them to the same pool in XenServer 6.5, so I guess the CPUs are compatible (enough). I am curious as to what has been done in order to mask the differences between the CPUs. I live migrated a VM from one to the other (8347 to 8393), and I noticed that the VM was reporting the old clock speed for the CPU... Does this mean that the faster CPU of the second server will look to the VMs as having the same specs as the older 8347, or will this cahnge when I reboot the VM? Is it better from a performance point of view to keep the two servers separated, not in a pool?

@scottalanmiller I was simply using those numbers as examples, actually. I have learned over the years that it's better to start low and increase as the VM needs more resources.

I might be using the wrong phrase here, but for consolidation reasons it is very handy to be able to virtualize for example 4 servers With 24 GB RAM each onto a XenServer/vSphere host With for example 64 GB RAM. Each VM will not use the full 24 GB at the same time, and will thereofre fit nicely within the physical 64 GB RAM. As we speak I use 160% of the RAM on my XenServer, and none of the VMs are starving for RAM. I Guess if all the VMs use all their RAM I will get into trobule, and I am at this point not aware what will happen then. Swapping, I Guess?

Hm... After making sure XenTools is installed in all the VMs on the server, I can actually see the RAM being decreased for the already powered on VMs as I power on the last VM -- it works as expected now that all VMs have XenTools installed. Thanks!

XenTools is missing from at least one of them. Could that be it? I am in the process of removing VMware Tools from one of the VMs and will now install XenTools...

I have just tried to start up another VM, and get this error in XenCenter: "The given VMs failed to release memory when instructed to do so"...

Hello again, community!

I have used VMware for years now, but have avoided becoming an expert ;-). I have seen how good it is at consolidating many servers onto one host, effectively dealing out lots of RAM while not consuming all of it in real life. One of my servers now has about 220 GB as granted, but only 125 GB (of 128) actually used. That is good.
Now, I have been starting experienting With XenServer for several reasons. One of them being that an old server was not able to install current version of ESX, but XenServer 6.5 installed fine. The server is more than 7 years old, but has 32 cores and 64 GB RAM, so it is too good to let go. Also, after adding a couple of other old servers I am able to do live (storage) vmotion for free. This makes XenServer attractive.
But, now I run into memory trouble. The one server I will use as example has 64 GB RAM. One VM has been given 32 GB RAM, and another 24 GB RAM. Now, trying to power on a third VM With 8 GB RAM fails, because I have used up all the RAM... Hm. That was an unpleasant surprise. Does this mean that XenServer cannot "overcommit" memory like ESX can? Or is there a setting I can change?

OK, now I have a bit of reading to do... Thank you for all the information! I might return with a question or two after doing some reading

@flomer said:

@scottalanmiller said:

@flomer said:

But, isn't virtualizing FreeNAS something that is generally adviced against?

Based on what? The rule is "virtualize everything." I know of no reason that FreeNAS should be physical.

I have read on the FreeNAS forums that they advice people not to virtualize, but it might have been specifically about ZFS.

I'm a bit confused at the moment... I was under the assumption that ZFS needed raw access to drives. For SMART?

@scottalanmiller said:

@flomer said:

But, isn't virtualizing FreeNAS something that is generally adviced against?

Based on what? The rule is "virtualize everything." I know of no reason that FreeNAS should be physical.

I have read on the FreeNAS forums that they advice people not to virtualize, but it might have been specifically about ZFS.

@scottalanmiller said:

@flomer said:

But, will this not lead to slower operation? There must be some overhead? And this should be the only VM on that server, then?

Yes but if you can measure it that would be shocking. There is effectively no overhead on the disk IO and all of your bottlenecks are from spinning disks and such. You still get all of your available threads, nearly all of your memory, etc. The CPU hit is nominal and the disk IO hit is nominal. The benefits are huge and the caveats are things you probably can't even measure.

But yes, the only VM on the server most likely. Virtualization won't cause performance issues. Consolidation might. But test it, you might get a lot of consolidation out of it too. All depends on your workload, hardware changes, etc.

But, isn't virtualizing FreeNAS something that is generally adviced against? And how to presen the entire RAID 6 drive to FreeNAS? By using several 2 TB disks and LVM? I guess ZFS is out of the question anyway, since I don't have direct access to the individual drives.

@scottalanmiller said:

@flomer said:

I still haven't heard from the reseller why the RAID controller didn't kick the drive out.

There is a really good chance, and I really mean VERY GOOD chance, that the threshold of "too many errors" was not hit until the reboot. Rebooting a system will cause changes in drive activity that could easily trigger the difference between "too few" and "too many" errors. I have seen this a lot.

Well, I actually rebooted the machine thinking it might help before I knew it was a failing drive. It seemed to help a little, but I guess I must just have imagined it getting better. Or at least the situation got just as a bad after a little while.

@scottalanmiller said:

@flomer said:

But, I have seen earlier on other DL380s that a drive will have an amber LED indicating that it is in "pre-failure" state, probably because of SMART-errors. That didn't happen here, and I have not seen a RAID before that has been so slow and troubled by a bad disk... I don't have that much experience, though... I will be interesting to hear what HP or our dealer will say about this. I also asked them if they think the RAID card is faulty. The ease of having a controller guiding you is sort of not present anymore, might as well buy an LSI HBA and go for ZFS. I woudl surely have been notified about this.

Any chance that you are using third party drives instead of HP drives? Non-HP drives will not fully report to the SmartArray.

I have not touched the RAID since setting it up almost three years ago, and all parts are HP parts. See below for snapshot of error message. The RAID is RAID 6, not 60, by the way...

I still haven't heard from the reseller why the RAID controller didn't kick the drive out.