Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 so my original installation of Xen Server was to 4 disks, raid 10. When we added the additional 4, dell did a "live" update to the raid configuration so that it added the capacity. That part looks fine but then from Xen Server I'm under the "assumption" it will see the Raid has changed automagically and expand but alas it didn't
So your saying I need to add a new SR? Is that different than expanding the existing one?
RAID is an underlying mechanism. Very underlying. So you have several layers on top that need to be configured in order for additional capacity to be available to things running on the server, like Xen.
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@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
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@black3dynamite said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
I have to look up the exact process but that sounds about right but because it's not worth it and he's trying to troubleshoot another issue I would literally just create a separate sr and call it thick provision and leave it at that
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@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@black3dynamite said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
I have to look up the exact process but that sounds about right but because it's not worth it and he's trying to troubleshoot another issue I would literally just create a separate sr and call it thick provision and leave it at that
I don't know what I'm saying - but I'm asking anyway - does he even have LVM?
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@Dashrender said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@black3dynamite said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
I have to look up the exact process but that sounds about right but because it's not worth it and he's trying to troubleshoot another issue I would literally just create a separate sr and call it thick provision and leave it at that
I don't know what I'm saying - but I'm asking anyway - does he even have LVM?
Xen server supports LVM but he may not have set it up for his storage repository
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@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@Dashrender said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@black3dynamite said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
I have to look up the exact process but that sounds about right but because it's not worth it and he's trying to troubleshoot another issue I would literally just create a separate sr and call it thick provision and leave it at that
I don't know what I'm saying - but I'm asking anyway - does he even have LVM?
Xen server supports LVM but he may not have set it up for his storage repository
It's the default to not use LVM, right?
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@Dashrender said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@Dashrender said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@black3dynamite said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 Been a while since I've used XenServer, wouldn't he need to power down the VMs, unplug the block device, and then use LVM to expand the storage?
I have to look up the exact process but that sounds about right but because it's not worth it and he's trying to troubleshoot another issue I would literally just create a separate sr and call it thick provision and leave it at that
I don't know what I'm saying - but I'm asking anyway - does he even have LVM?
Xen server supports LVM but he may not have set it up for his storage repository
It's the default to not use LVM, right?
The default is LVM... They should probably update that.
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@Dashrender idk. Never really paid that close attention to it.
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@DustinB3403 Yea because I've seen all the advances made on 8 release, so I anxiously want to move to that. But I know until I can get another server here its a bit tough.
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Im thinking of getting a 3rd server that can just have enough storage to move my vm's over, then nuke the old host one by one or upgrade them. I'm not sure if 7.1 is upgraded to the XCP-NG releases.
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12 TB of storage and 128GB or RAM isn't much, I have 24TB raw in my lab alone, the RAM I don't need and don't have.
You could purchase a cheap server and get that much capacity for cheap.
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So you have dual socket CPU with 128 GB of RAM. Which CPUs do you have?
In XenCenter you can select the host and then it's under the General tab and the CPUs section.And then 16TB disks in 8x2TB config with 7200 rpm SAS drives. So 8TB usable space and your using close to 50% now?
Do you know how much cache your H730 RAID controller has?
VM's are thin provisioned and it's a mix of Windows and Linux VM's. How many VMs do you have running and how much of the RAM is provisioned now?
To get some info on performance, in XenCenter select the host and go to the Performance tab. Right click on the graph and select Actions>New graph... Make a graph with IOwait on your SR. Post a screen shot of it together with CPU performance when you are having sluggish performance.
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@DustinB3403 yea I know it’s not a lot. We are a somewhat small non profit. Honestly I would rather max out both servers ram wise and switch to all SSDs since the price is literally the same for Nearline SAS.
I’m assuming the thin provisioning is the culprit but that’s only an assumption. I recall reading that it would slow down in time vs thick provisioning being a bit speedier.
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Technically right now the host is 16 Tb raw storage and 8 Tb usable (maybe a notch less) since it’s raid 10 but the XenServer HVM doesn’t see the extra 4 Tb yet. I dunno why 🤨. See I’ve done capacity expansions before on other additional single drives no problem. But on the raid I’m lost. Since it was “added” capacity from bios, I assume the hyper visor would just “see” it.
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@Pete-S that I can do.
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
Since it was “added” capacity from bios, I assume the hyper visor would just “see” it.
Once the RAID is expanded, you would generally need to add or grow a logical volume to preset to the hypervisor. This isn't a RAID problem, it's an LVM problem. That you have RAID is not a factor, since that has already grown. That's no longer part of the equation.
To verify, go into your RAID management tools and see what size RAID array it believes that it has. Then see what size LV it is offering to the hypervisor. Sounds like they don't match.
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
I’m assuming the thin provisioning is the culprit but that’s only an assumption. I recall reading that it would slow down in time vs thick provisioning being a bit speedier.
By only a TINY bit, and only during times of thin expansion. If you are seeing a performance issue, then that's not it.
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
Things are working but we are definitely seeing plenty of times where the speed is not where it use to be.
Disk slow as they become fragmented (not a problem for modern SSD, but spinning rust still has this), as contention increases (more workloads slows what is available for everyone), and as the disks fill up. Once you are past 85% capacity, storage gets slower.
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
I'm just deeply assuming the thin provisioning is the culprit but that's without proof, only assumptions.
Can't be, so that can be ruled out right now. Thin provisioning has so little overhead, hence we you "never" turn it off except in really specific circumstances and those are pretty obvious (large scale, crazy high performance databases, for example.)
There is no possibility that thin provisioning is a factor here.
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@krisleslie said in Having sluggish performance on my Xen Server VM's, looking for suggestions to boost performance:
@DustinB3403 so my original installation of Xen Server was to 4 disks, raid 10. When we added the additional 4, dell did a "live" update to the raid configuration so that it added the capacity. That part looks fine but then from Xen Server I'm under the "assumption" it will see the Raid has changed automagically and expand but alas it didn't
So your saying I need to add a new SR? Is that different than expanding the existing one?
You should not expect this to show up as Dell (LSI) RAID controllers contain a LVM layer. Expanding the RAID only makes the RAID card's LVM ready to be configured. Until that is done, it should be impossible for the hypervisor to see the additional storage. The RAID card doesn't know how the additional capacity is meant to be used, so it can't do anything else with it until you tell it what to do.
This is the caveat with the power of LVM on the hardware RAID.... it gives you awesome benefits like making a single RAID array that you can present as an many disks as you want to the OS. But the caveat is that you have to configure it every time, as there is no possible default setting.
