Jump to content
XPEnology Community

ESXi - datastores vs RDM vs pass through disks


Backslash
 Share

Recommended Posts

Hi all,

I'm going to rebuild my server to be an ESXi machine and run DSM on top of that. I won't be running any other VM's except for maybe a home automation VM or something.

 

I'm trying to figure out what will be the best disk configuration going forward, whether I create datastores from the disks in ESXi, map the disks as RDM disks to the DSM vm, or buy a sata controller and do pci-e pass through.

 

Any insight into pros/cons would be great. Ideally I'd like to not spend any more money but open to suggestions.

 

Thanks everyone!

Link to comment
Share on other sites

Well the only way that DSM will have smart data from hardrives, is if you passthrough a controller to your DSM VM (it won't work w/ RDM).

 

If you use virtual drives (on a datastore) for your array, then you won't be able to use your disks with systems outside esxi. Like if you wanted to move the disks to real synology system. Or if wanted to mount your array in Linux (outside of esxi), to recover a broken array, ect. I'm not sure about transfer speed differences.

Link to comment
Share on other sites

RDM disks can be also moved a real synology system or connected to a passthrough controller...

No native SMART support for RDM disks... even though smartctl is able to read SMART data, but appearently the diskmanager uses something differnt to query SMART data and fails.

Link to comment
Share on other sites

Thanks for the replies!

 

So the general gist is that if I want to move my disks to a physical Symbology server (or to another physical Xpenology BareBones server) I need to use RDM or Pass through. And if I want SMART data I need to use Pass through.

 

If, however, I plan on staying with ESXi for good virtual disks are fine?

 

Sent from my SM-G928I using Tapatalk

Link to comment
Share on other sites

I still wouldn't recommend to use a proprietary disk format...

 

I started with RDM and ended up adding LSI 2008 controllers. Though, both my ESXi hosts use a xeon cpu, which is required in order to use directIO in ESXi.

If you pass through a controller, you have to assign a fixed amount of memory - the vm won't be able to use ram balooning anymore (=only consume as much host ram as the guest uses).

Link to comment
Share on other sites

If you pass through a controller, you have to assign a fixed amount of memory - the vm won't be able to use ram balooning anymore (=only consume as much host ram as the guest uses).

 

That's a good point - I allocated 4GB to my DSM VM, but I have 24GB in the server, so it's no problem - it may be an issue for others.

 

Note that you also lose the ability to hot plug devices to VM using DirectIO - that's why I also pass-through a cheap PCI-E USB3 card to DSM.

Link to comment
Share on other sites

I'm a complete noob to all this and have a HP microserver gen8 with a P222 controller, 16GB RAM, no Xeon CPU (yet)

 

I've got it running ESXi 5.5 and basically have my VMs running off a raid1 2X3TB, I was thinking of using the spare 2 slots and adding an additional raid 1 for pure storage for a DSM VM

and wondering my options.

 

Not sure if I can use the controller to host my VMs on the 1st raid 1 and have a passthrough or RDM for the 2nd RAID 1, could the controller handle it? I assume the easiest it just to add a second datastore and be done with it. however keen to go for the best solution.

 

thanks in advance for your opinions

 

Alzoo

Link to comment
Share on other sites

With DirectIO Passthrough vSphere hands over complete control of the disk adapter to the VM. Any disks attached to the adapter can only be seen within that VM.

 

RDM is similar, but at the disk level. So I think you could map the 2nd RAID array to a vmdk using RDM - However, I've not tried this, I went straight down the DirectIO route as I had an existing SHR array to migrate from a physical installation of DSM.

Link to comment
Share on other sites

With DirectIO Passthrough vSphere hands over complete control of the disk adapter to the VM. Any disks attached to the adapter can only be seen within that VM.

 

RDM is similar, but at the disk level. So I think you could map the 2nd RAID array to a vmdk using RDM - However, I've not tried this, I went straight down the DirectIO route as I had an existing SHR array to migrate from a physical installation of DSM.

Hey berwhale,

Any reason I wouldn't be able to create and SHR array with DSM6?

 

When installed I don't get the option to choose SHR. I am forced to create a raid group first and then volume after that. But irs only standard raid groups I can create.

Link to comment
Share on other sites

@Backslash - I think you have to select the 'quick' option when setting up the volume. You only get offered RAID with the custom option.

That's odd.

I don't get the choice. I have to create a raid group and then volume second.

 

Did you use the ova/ovf or install manually with the ISO?

 

Sent from my SM-G928I using Tapatalk

Link to comment
Share on other sites

Unfortunately I don't see any VMDirectPath I/O pass-through devices on my HP Microserver so its RDM for me

 

thanks for the info

Link to comment
Share on other sites

Yes, but the whole server is only £20 more than buying the CPU on it's own. Also, you can fit more drives in the T20 - 2x 2.5" in the optical bay and 4x 3.5" in the normal bays, plus there's space to add one 3.5" or two 2.5" drives in the floppy drive hanger. There's also room to add an internal drive rack if you have some DIY skills.

 

I have 2x 2.5" drives as ESXi datastores and 4X 3.5" drives passed-though to DSM. All I had to buy was a couple of SATA power splitters.

Link to comment
Share on other sites

Yes, but the whole server is only £20 more than buying the CPU on it's own. Also, you can fit more drives in the T20 - 2x 2.5" in the optical bay and 4x 3.5" in the normal bays, plus there's space to add one 3.5" or two 2.5" drives in the floppy drive hanger. There's also room to add an internal drive rack if you have some DIY skills.

 

I have 2x 2.5" drives as ESXi datastores and 4X 3.5" drives passed-though to DSM. All I had to buy was a couple of SATA power splitters.

If only the T20's were available in Australia. I'd hand over my cash right now! Haha. MN

 

Instead I'll be having to do a custom build.

 

Sent from my SM-G928I using Tapatalk

Link to comment
Share on other sites

Unfortunately I don't see any VMDirectPath I/O pass-through devices on my HP Microserver so its RDM for me

 

You need CPU support for DirectPath I/O - a Xeon or an i5+ I think.

 

Xeon and i3 (not i5).

 

Intel yielded to HP/DELL/Lenovo and enable direct I/O with an i3 CPU so the manufacturers can sell cheap servers for small businesses.

Link to comment
Share on other sites

Unfortunately I don't see any VMDirectPath I/O pass-through devices on my HP Microserver so its RDM for me

 

You need CPU support for DirectPath I/O - a Xeon or an i5+ I think.

 

Xeon and i3 (not i5).

 

Intel yielded to HP/DELL/Lenovo and enable direct I/O with an i3 CPU so the manufacturers can sell cheap servers for small businesses.

 

That's only true for:

- 4th gen i3 >= i3-4010U

- 5th gen I3

- 6th gen i3

 

And almost all i5's do -> https://en.wikipedia.org/wiki/List_of_I ... processors

The statement was fit for a HP microserver Gen8, which has no support for >= 3rd gen CPUs.

Link to comment
Share on other sites

  • 1 month later...
Yes, but the whole server is only £20 more than buying the CPU on it's own. Also, you can fit more drives in the T20 - 2x 2.5" in the optical bay and 4x 3.5" in the normal bays, plus there's space to add one 3.5" or two 2.5" drives in the floppy drive hanger. There's also room to add an internal drive rack if you have some DIY skills.

 

I have 2x 2.5" drives as ESXi datastores and 4X 3.5" drives passed-though to DSM. All I had to buy was a couple of SATA power splitters.

 

 

berwhale, what controller cards are you using?

 

 

I've just got a T20, and want to move over my 4 hard drives from my N54L, and add a couple more but it seems the controller card I got pexsat32 and it (https://www.startech.com/uk/Cards-Adapters/HDD-Controllers/SATA-Cards/2-Port-PCI-Express-SATA-6-Gbps-Controller-Card~PEXSAT32) doesn't seem to be compatible with DSM 5.2 as I can't see any hard drives in DSM when it's added to pass-through.

Link to comment
Share on other sites

I'm using a card with a Marvell 88SE9215 chipset...

 

http://eud.dx.com/product/iocrest-marve ... -844282997

 

 

Okay cool, ordered the same one but Syba branded from Amazon, should have it this evening. :smile:

 

 

Assume I should just be able to plug in my existing drives and pass-through to a VM that is of the same DSM version number and the volume will show up fine?

Link to comment
Share on other sites

 Share

×
×
  • Create New...