vSphere Availability

As this fault tolerant VMware is using is not new (Marathon offers this since the late 90's and they run XEN for virtualization since a few years, Stratus) I would like to know if vSphere 4 takes care about the virtual disks, too. At least with Marathon's FT and HA Server you don't have to take care about the mirroring of your disks. That even works without a SAN as you can use local disks for that and for distances about 160 km.

What about vSphere 4? Can it transparently switch over and guarantee continouos computing for the vDisks, as well? If so, what is needed to achive this?

Do I have to use a SAN for FT?

Do I need to have SAN mirroring in place (like EMC SRDF) or other mechanisms like storage virtualization (like EMC Invista, as SRDF transparent fail over is a thing of its own)?

Can I use separate SAN boxes and mirror the vDisks via VMware mechanisms?

AWo

VCP / vEXPERT 2009

Hello.

>Do I have to use a SAN for FT?

Reading through the vSphere Data Migration Checklist pdf, it appears that shared storage (FC, iSCSI or NFS) is a requirement for FT. There is some really good insight in this document about the requirements and realities of using FT.

As I posted other forum, vSphere 4 seems to pick up the slack of pieces and puzzled them together with one good software but some of the features can be accomplish with 3rd party product and plugins. :smileysad: unfortunately, the requirements for FT to function properly is fully clustered with shared resources as mentioned in the guide. But its so common that all enterprise application like Exchange, SQL and Oracle shouldn't be on standalone host :smileyhappy: but does it support RDM?

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Regards,

Stefan Nguyen

VMware vExpert 2009

iGeek Systems Inc.

VMware, Citrix, Microsoft Consultant

Hello,

I believe it is still single VMDK only not RDM support and yes you need shared storage or it does not really make sense.

Best regards,
Edward L. Haletky
VMware Communities User Moderator, VMware vExpert 2009
====
Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.
Blue Gears and SearchVMware Pro Blogs -- Top Virtualization Security Links -- Virtualization Security Round Table Podcast

I believe it is still single VMDK only not RDM support and yes you need shared storage or it does not really make sense.

In terms of the actual VMware possibilities, yes. But not in general. People who needs such a fault tolerant level and do not have a SAN in place can't use VMware FT then, but they could use Marathon with XEN on it.

I think it is an important feature that the instance which takes care about the fault tolerance should do that for all parts of the system. If we would loose one datacenter on our site it doesn't help if the guest has the ability to continue semlessly, but the disks can't follow as there must be to be a manual SAN switch performed first. Of course, there might be solutions which provide that mechanism. But that would mean that this switch-over is out of the control of vSphere (beside other links like additional costs). And that is where I would expect it to be: a single instance to control the whole process.

And there are already solutions which provide that even without a shared storage.

AWo

VCP / vEXPERT 2009

Hello,

I agree that all those items would be great, but given how FT was implemented the rest is not supported. VMware FT at this time has some serious limitations and requires shared storage. FT does not hook into SRM or SVMotion yet. It relies on your storage staying up. Given this, the rest does not make sense..... However, on second reading it is definitely easy to misunderstand what I wrote. I did as well.

VMware FT is not 'FULL Fault Tolerance' as you get with Marathon, and tempest style systems. It is a way to alleviate the need to create clusters of VMs (MSCS) to provide a high availability option. Could it eventually LockStep storage? Perhaps, I would think VMware is researching it but its quite a bit of work.

Best regards,
Edward L. Haletky
VMware Communities User Moderator, VMware vExpert 2009
====
Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.
Blue Gears and SearchVMware Pro Blogs -- Top Virtualization Security Links -- Virtualization Security Round Table Podcast