Unable to create RDM

[JimPhreak]

I'm having trouble creating an RDM based on the steps in this link. I keep getting a "missing required argument" error when I try.

Anyone have experience with this?

 

[whitey]

That's the 'harder way' to do it for sure. Use the GUI. Screenies attached.

 

[whitey]

One more:

 

[JimPhreak]

I should have mentioned that I'm trying to create the RDM for a locally attached SATA drive so the Raw Mapping Option is greyed out when trying to add it via the vSphere Client.

 

[whitey]

Ohh, my bad yeah my example was using a iSCSI volume across the vSphere SW iSCSI initiator to a FreeNAS zvol iSCSI backed disk. No experience w/ your type of config that other than saying DON'T do it...no seriously don't do it unless you have DANG good reason to. There are more proper ways of doing RDM's and oh BTW there are less and less (very corner cases) for uses of RDM's. Do tell me yours if you would be so kind?

2cents

 

[JimPhreak]

Ohh, my bad yeah my example was using a iSCSI volume across the vSphere SW iSCSI initiator to a FreeNAS zvol iSCSI backed disk. No experience w/ your type of config that other than saying DON'T do it...no seriously don't do it unless you have DANG good reason to.

2cents

I do have a good reason. I need to present a hardware RAID1 device attached to my onboard storage controller to unRAID for use as a cache drive. I can do a cache pool on unRAID but right now you can only use the btrfs FS with that pool which has terrible performance and makes a cache drive virtually useless. From what I've been reading there's no other way to do it.

 

[whitey]

Ewwww, have fun with that, talk to any VMware stg eng 'deep in the weeds' and 99% will vote to steer clear of RDM's unless absolutely necessary...with that being said I know nothing about unRAID.

GL!

 

[JimPhreak]

Ewwww, have fun with that, talk to any VMware stg eng 'deep in the weeds' and 99% will vote to steer clear of RDM's unless absolutely necessary...with that being said I know nothing about unRAID.

GL!

What's the reasoning to be so against it?

I can only go with what the experts on the unRAID forums have said and given my situation there's no alternative.

 

[whitey]

Mgmt nightmare at scale, mis-conception that an RDM will provide 'better perfoamnce' than a VMDK, migration nuiscances of data in/out of RDM's if you want to convert, potential corrupted/stepped on volume if SAN eng has a bad day or presentation is mis-configured (data/written over) etc.

That being said they 'can' be handy for DR scenario's, MSCS clusters/other clustering scenario's although there are many times more elegant way to do clustering that relying on technologies that require this, DIRECT SAN lun access for tools/apps/san mgmt control-plane that demand/require hooks to the RAW lun. I could go on...lived nightmares in an ENT env too long and we and now almost fully converted out of that mess and since vmdk's can grow to 62 TB now (supported array of course), really a non-issue/kinda defeats the whole RDM purpose (although I must confess again I have seen more mis-configured or falsely assumed that a 'higher-performance profile/tier or more native access to the disk was gonna be night/day difference...sadly VMFS and other cluster/shared filesystems over a reasonable dedicated stg network fabric can keep up to snuff and drive insane I/O...many times greater than an single local disk RDM certainly :-D wink wink/no hard feelings...I get you have a 'specific use case'

(disclaimer we typically we're using FC 8 Gbps carved of SAN fabric LUNs to vSphere so not really apples to apples...I digress...) Even my iSCSI RDM volume to yours is quite different to your approach but more similar to the FC RDM approach.

 

[RyC]

When I used RDM, I followed Tip #3 from this topic on the unRAID forum to create the RDM pointer for a SATA drive. ATLAS My Virtualized unRAID server

I tried it out with ESXi 6 and it still seems to work.

 

[JimPhreak]

When I used RDM, I followed Tip #3 from this topic on the unRAID forum to create the RDM pointer for a SATA drive. ATLAS My Virtualized unRAID server

I tried it out with ESXi 6 and it still seems to work.

Thanks for the reply. I'm familiar with that thread but never thought to check it for this issue. Luckily for me I actually got it to work using that exact method through simple Googling and I'm all set.