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We have a Synology NAS RS810RP+ running DSM 2.3-1161 and there are several block level iSCSI devices configured. Each of the devices is used as iSCSI harddrive for a different ESXi VM.

(Every VM has one device and every device belongs to one VM, there is no sharing of devices between VMs)

We have assigned a seperate LUN to each iSCSI, so we have now:

VM0 <-> LUN 0
VM1 <-> LUN 1
VM9 <-> LUN 9

I guess every VM and every iSCSI device in our configuration needs a different LUN? But there are only 10 LUNs (0 to 9) possible in DS 2.3, this means we can only have 10 VMs living on the NAS?

We do not have all VMs running at the same time, so the resources are not an issue.

How can we host more than 10 VMs on the NAS?

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up vote 1 down vote accepted

Instead of allocating an iSCSI LUN for each VM, create a single NFS filesystem and then place your VM images on this filesystem. Now your limitations are simply capacity (how much space do you have?) and performance (can your NAS keep up with the i/o requirements of your VM infrastructure?).

This document form VMware addresses NFS vs. iSCSI vs. Fibre Channel performance:

The short summary is that NFS performs roughly as well as iSCSI in almost all situations.

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This is very interesting. And according to figure 6 we will even win CPU performance on the ESXi host system because NFS is cheaper compared to software iSCSI. – mit Nov 19 '10 at 3:57
If you are happy with this answer would you mind accepting it? Thanks! – larsks Nov 19 '10 at 14:12
oh .. sorry for the delay – mit Nov 30 '10 at 16:42

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