vmware iscsi targets

datatechdc
datatechdc used Ask the Experts™
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i have a qnap nas that was setup for me and ISCSI targets configured.

i have VMs running on the actual qnap through the shares created on the qnap.

i have these iSCSI targets created but i dont know why.

what is the purpose of iSCSI targets and adding them to the VMs so they appear as drives?
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VMware and Virtualization Consultant
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Commented:
It allows your virtual machines to add iSCSI based block storage, and get round some limitations of virtual disks. (which would also be stored on the Qnap).

Test which perform better,

1. a virtual disk (VMDK) stored on the Qnap NAS.
2. an iSCSI target on the Qnap.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
disadvantage is you cannot VMware snapshot, an iSCSI targets as it's ben setup.
Your ISCSI targets were probably created so that your VMWare ESX/ESXi server can use them as local hard drives, to store the actual virtual machines on them.

You didn't use it in such way, but used SMB sharing to get the same effect. Using ISCSI is better since it gives you block-level access to the volume (via IP) so your HDD appear as actual HDD drives, rather than just shares.

Another thing you can do with ISCSI tagrets is to use them _inside_ your virtual machines to give those machines access to a HDD via IP.

What ISCSI actually is: it's a SCSI protocol (the same as on SCSI HDD cable) but this one works over IP and can use ethernet as a transport. So you can "connect" a drive (well, not actually a HDD, but rather a logical volume) to some computer (via ISCSI initiator software) and that computer will see this drive as a local HDD.
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Btw, QNAP is great with ISCSI, and ISCSI usually provider better performance with less CPU overhead.

The purpose to use ISCSI to give a virtual machine access to the drive is in several:
- you don't need to consume local storage (which may be more expesive, or may be limited in space )
- you can easily access it from another location in case your VM goes down, or move it between the VM's without copying
- the hardware that hosts your ISCSI target may have a backup solution, be mirrored, be replicated, etc.
- ISCSI volumes can be resized, even online on QNAP
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
you could be using NFS on the Qnap? (as you state shares?)

Author

Commented:
ok so the VMs are stored through shares on the QNAP. this seems to be working just fine.

the iSCSI must be setup to be used as local drives.

can i attach a single iSCSI target to multiple servers? (i have two terminal servers and will keep the data files on the iSCSI disk so no data is actually stored on the VMs).
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
No you cannot attach a single iSCSI targetbto multiple Windows VMs, if you do you will get corruption.

it can only be done with clustering, but only one computer has access at a time.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
if you need to access storage simultaneously use a nas, windows ahares or nfs.

Author

Commented:
i can't link my AD to the qnap NFS shares though can i?

Author

Commented:
or is it better to just use the iSCSI target on one of the servers and just change the path of the other server to point the directories?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
It depends on what options are available on your Qnap, Windows Shares are probably configurable, because Qnap could be added to AD domain, NFS is different.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
what do you want to do?

what VMware product are you using?
> can i attach a single iSCSI target to multiple servers? (i have two terminal servers and will keep the data files on the iSCSI disk so no data is actually stored on the VMs).

You actually could, but this would likely corrupt data stored on the ISCSI partition. So you have to be careful NOT to :)
ISCSI provides block level access, to use concurrent access use SMB or NFS (sharing)

> or is it better to just use the iSCSI target on one of the servers and just change the path of the other server to point the directories?

Depends on what you need. When you have an ISCSI target mounted on 1 server, then this server can do sharing. If this server is a domain member this sharing will actually work much better then the case when you would join QNAP to the domain and use SMB on QNAP (tested & restested, NAS devices usually have issues on the long run when joined to an AD domain).

But, in terms of simple file sharing (forget AD domain, just sharing) then sharig via QNAP is a better option (one less point of failure).

Author

Commented:
my goal is to be able to create multiple terminal servers and have one datastore for the users data (home directories, mapped drives, etc). these must have AD permissions enabled. i have close to 40 users and plan to add more.
Then I suggest you run an ISCSI initiator on one of your servers and (VM's or not) and connect to the ISCSI target, to get the drive locally avaliable.
Then, create the needed datastores on this drive. This will work fine, all AD permissions will work without isses - guarranteed.
Update: I'm not sure if I explained correctly - this server can be either one of the terminal servers, or a completely different server (VM or not). The user profiles, etc, should connect users using an UNC path (so it can be accessed from any terminal server)
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Okay, if you are running VMware vSphere, I would test which performs better for you with your Qnap.

1. NFS (possible current setup as you refer to directories)
2. iSCSI

VMware ESX can connect to both, you may find iSCSI performs better.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
if you are using NFS or iSCSI, you may also get better performance, by using and enabling Jumbo Frames, (but make sure your network and Qnap NAS supports Jumbo Frames), berfore enabling on ESX.

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