Synology-iSCSI-VMware

[schoondoggy]

I realize iSCSI is overkill for the average home server environment, but if you work with small businesses Synology has a nice iSCSI solution to go with VMware.

"The cool thing is that the Synology DS412+ is on VMware’s Hardware Compatiblity List and also supports the vStorage API for Array Integration (VAAI). The DS412+ supports Block Zero, Full Copy, HW Assisted Locking and Thin Provisioning."

http://www.viktorious.nl/2013/05/28/vsphere-5-synology-ds412/

[ikon]

iSCSI is definitely a pretty cool technology. I've seen them, but never had one set up at home. One of these days....

 

Question: Can more than one client computer access the same iSCSI target? Concurrently?

[schoondoggy]

Yes, the number is based on the performance of the array. This Synology DS412+ is on the low end, 32 iSCSI targets and 256 LUN's, and it does support snapshots, clones and thin provisioning.

[ikon]

Thanks.

[microsvr.de]

Watch out: iSCSI is a provided as a block device! You won't want to access the same target from two different servers, since they would overwrite each others data! It's like providing the same harddisk to two servers - how would they know where to write and which areas to leave alone? Use two iSCSI targets in that case - or use NFS in that case!

[schoondoggy]

You are correct. That is good clarification. In looking back at my answer, I was referring to multiple clients hitting the same Synology box, not the same target or lun. Thanks!

[ikon]

Great clarification guys. So my worry is justified after all. Good to know. Thanks.

[keeplearnin]

Yes the iSCSI piece of the Synology is a great feature! I have seen some examples of some nice home lab installs of users simply installing ESXi on a machine using just a USB thumb drive and a chassis with no hard drives installed whatsoever. Once ESXi is installed on the USB thumb drive and booted up you simply point the VMware host at the multiple iSCSI targets that can be created with the Synology NAS. This is more in line with a corporate infrastructure but at the same time is very handy for a home setup. Especially if you have critical VM's that need to be backed up regularly. Those critical VM's end up residing on lets say a 4 bay Synology setup with hybrid raid and can withstand drive failure. This is of course in sharp contrast to what a typical home user playing with ESXi has. The typical home user may just have a VMware host loaded with a bunch of hard drives running VM's on them. This makes it much harder to backup these VM's because that VM may be residing on a single drive in a VMware host. If the single drive fails that your running your single instance of lets say MSWHS 2011 you would be a sitting duck for that single drive to fail. However, for the crew here at WHS, I have to imagine those that are running VMware hosts for their critical data probably have at least a raid 1 or a raid 5 setup as one big hard drive where all their VM's are sitting. Some food for thought though.

[viktorious]

Hi all,

 

I am the author of the article you're referring to. Although iSCSI indeed presents a block device, it is a good idea to share the block device (LUN) between more than one servers in a VMware environment: actually this is common practice. VMware uses the VMFS file system, which is a multi-access (or call it clustered) file system which is designed to deal with different servers accessing the same iSCSI volume/LUN. With the paid version of VMware vSphere you have access to some cool features like vMotion, DRS and HA which (for example) enables you to move running virtual machines between different servers (=ESXi hosts). This is very beneficial e.g. for minimizing downtime in case of maintenance. VMware High Availability (HA) kicks in, in case of server failure. In this case VMware will restart VMs automatically on another server....this of course requires access to the LUN the VMs resides on. 

 

VMware used SCSI reservation version 4 of the product, but nowadays (version 5 and newer) leverages something called ATS locking. More information on ATS locking is in this article: http://blogs.vmware.com/vsphere/2012/05/vmfs-locking-uncovered.html

 

VMware also supports NFS to place your VMs on, which is more like a file share (and also support vMotion, DRS and HA). 

 

You can just try VMware vSphere for 60 days for free, just download the product from vmware.com. You will need ESXi for virtualization and vCenter server to use vMotion, DRS, HA etc. vCenter is available as a so called "virtual appliance", which is a pre-configured (Linux) virtual machine and is deployed quite easily on an ESXi server. 

 

Hope this helps!

 

Best regards

Edited October 25, 2013 by viktorious

[ikon]

Nice post victorious. So, if I read it correctly, the multi-access to an iSCSI device is a function of VMware, not iSCSI itself, correct?