The Storage Architect » Microsoft

Why Does Microsoft Hyper-V Not Support NFS?

Chris M Evans — Thu, 02 Jun 2011 06:27:40 +0000

I recently wrote an article covering storage for virtualisation and was surprised to find out that Microsoft does not support the use of NFS shares with Hyper-V. At first I thought perhaps I was doing something wrong and that my configuration was in error. But after a lot of lab testing and eventually finding some obscure forum posts, I’ve concluded that NFS cannot be used for storing Hyper-V guests. But why?

Client for NFS

Microsoft has supported an NFS server and client within Windows for some time. In Windows Server 2008, the Client for NFS can be added through the “Services for Network File System” role. This creates a new MMC plugin on the start menu that allows administration of both Client and Server services for NFS. From that point on there’s not much to configure in the GUI and all NFS shares are mapped via the command line, or within WMI for Windows Server 2008 R2 (look for future posts describing NFS installation and configuration).

Hyper-V Fail

Any attempts to create Hyper-V guests fail with the error code shown in the screenshot attached. I’ve tried lots of options; pre-creating the VHD, importing the guest and so on, however all fail to allow a VHD to be created. Where does this leave me? Well, I can fall back to standard block-based Fibre Channel and iSCSI LUNs but this is potentially limiting if I’m looking to be more efficient with my Hyper-V installation. SCVMM 2012 for instance assumes I’m storing VMs on an entire single LUN as it uses LUN snapshots to replicate virtual machines. To make this kind of configuration work best, I’d need a storage system that does LUN level thin provisioning; this escalates my costs somewhat.

So the question is, why would Microsoft put in such a restriction? It’s not as if network share-based guests are totally banned as I can use CIFS to store them. Of course I wouldn’t want to do that because CIFS has some severe performance and integrity limitations that make it unsuitable. Perhaps it’s just that Microsoft still don’t “get” storage. After all, the latest recommendations for Exchange 2010 are to use DAS. Redmond needs to embrace the use of storage agnostic connectivity for Hyper-V; it’s these kind of features that keep VMware ahead and for many will make ESXi a preferred option.

Comparing iSCSI Targets – Microsoft, StarWind, iSCSI Cake and Kernsafe – Part I

Chris M Evans — Mon, 11 Apr 2011 21:37:51 +0000

This week, Microsoft released their iSCSI Target software for general availability. Previously this had only been available for installations with Windows Storage Server via OEMs. Now anyone with Windows 2008 R2 can install and use the software without restrictions. However, there are already a number of other iSCSI target software offerings already on the market, most notably from StarWind, iSCSI Cake and Kernsafe, so how does the Microsoft offering stack up? In this series I’ll look at each product and compare features and functionality, starting with Microsoft.

Installation

Installation of the Microsoft Target is pretty simple; it can be downloaded here: Microsoft iSCSI Target, then follow the instructions.

Configuration

The Microsoft Target is configured through a MMC plugin that can be found under the Administrative Tools folder from the Start Menu (see screenshot 1). As the management tool uses a vanilla MMC window, it’s rather basic in appearance but follows standard conventions of right-click options to select properties or using the Action menu item. For instance, right-clicking on the Microsoft iSCSI Software Target displays a context menu and Properties option, leading to a two-tab dialog box. This allows the IP and iSNS details to be specified. In my example (screenshot 2) I’ve tied the Microsoft Target to a single IP address as all of the Target software products are deployed on the same server. There doesn’t appear to be an option to change the listening port, which defaults to 3260. iSNS server configuration is pretty simple, consisting of a list of either IP address or server names (screenshot 3).

Targets can be created by clicking on the iSCSI Targets tree item and selecting Action or right clicking. The configuration wizard asks for basic details such as the target name and default security details; specifying “*” for the IQN provides open access. In my test environment I created two targets, target0 and target1. These are shown in screenshot 4. The properties for a target allow configuration of security/authentication, performance parameters and virtual disks. Virtual disks use the VHD format and can be either fully provisioned or differencing. Unfortunately thin provisioned VHDs are not supported, which is disappointing (see screenshot 5). Once created, virtual disks are associated with a target and exported for use. One or more LUNs can be associated with a Target (as is standard with SCSI). These appear to the hosts as separate devices. The benefit of having multiple LUNs to the same target is that security is performed at the target rather than LUN level. Therefore access to one or more devices can be performed once on the Target. Screenshot 6 shows the two targets configured and idle (no connected hosts), with screenshot 7 showing a single target login. There doesn’t appear to be a way to find the logged in initator for a target although this may be available via WMI (still under investigation).

Snapshots

A point in time (PIT) copy of a LUN can be created using snapshots. Each snapshot represents a copy of the LUN at the time the snapshot was taken and can be used to return the LUN to a previous state. Alternatively the snapshot can be exported via another target or mounted to the iSCSI Target host itself. Either way, these LUNs are read-only copies and can’t be modified. Screenshots 8 and 9 show the snapshot list and a schedule to create a daily snapshot of Virtual Disk 0.

Summary

The Microsoft iSCSI Target offers basic functionality with the ability to add snapshots. Not being able to use thin provisioned VHDs is disappointing, however the underlying filesystem could be placed on thinly provisioned disks, but that may defeat the point of presenting storage using the iSCSI Target. Of course the iSCSI Target is free and free is (almost) always good.

Next post: StarWind iSCSI Target

Microsoft Q&A Session: IP Expo 2010

Chris M Evans — Thu, 02 Dec 2010 10:00:10 +0000

Before IP Expo this year, I was invited to a Q&A session with Zane Adam, Microsoft General Manager for Azure. I’ve not posted any video from the event (yet). Fortunately Microsoft have saved me the effort and posted a few clips online. Here’s one video with a few interesting questions.

Enterprise Computing: Hitachi Enters The Cloud

Chris M Evans — Wed, 14 Oct 2009 08:01:15 +0000

Yesterday Hitachi Data Systems (HDS) used SNW USA to release information on their proposed cloud strategy, referred to as “Agile Cloud”. Everyone believes they need a cloud story and clearly Hitachi are no different.

Taken from the presentation I was given last week, is the following picture. This pretty much sums up Hitachi’s approach; make a virtue of the technology they have today around virtualisation and revamp their Content Archive Platform as a generic content platform – HCP.

Most of the things you’d expect are there – multi-tenancy, consistent name spaces, security, data tiering, REST interface to the HCP platform, but one or two differences stuck out for me. Firstly Hitachi are not about to get into the business of being a cloud services provider (CSP), like EMC, Microsoft, Amazon et al, but rather are making their technology available to other service providers to take up this challenge. Second, they are not betting on commodity solutions for data storage (e.g. Atmos) but are assuming Enterprise customers will want the same level of reliability they currently enjoy on existing Hitachi hardware.

With stories in The Press regarding data loss in cloud offerings ringing in everyone’s ears, there’s sure to be an increased focus on transparency regarding data security – not from an access point of view but on the use of technologies like RAID, backup and other methodologies cloud providers will implement to ensure data loss doesn’t occur. It’s also an opening for increasing the price and breadth of service offerings – a tiered approach to cloud storage provision as clearly one size/protection level doesn’t fit all.

Bl** Hyper-V!

Chris M Evans — Thu, 16 Oct 2008 12:00:00 +0000

Well, I wasted 3 hours of my life last night trying to get Hyper-V working on one of my PC/servers. Admittedly it’s an ancient 2 years old, only has PCI-Express, SATA-II support and up to 4-core Intel processors, but for some reason, my attempts to install Hyper-V would get just so far and fail with a cryptic 0x8007045D error.

As a seasoned professional, I tried the obvious – shouting at the PC, kicking the PC, snapping at my children as they came in to ask innocent questions, then as a last resort I tried using different installation media, screwing about with BIOS settings and so on.

None of it worked. The error code, according to Google, seems to be hardware related, but I’ve no idea where and Hyper-V being a complex high-quality piece of software gave me no clues. Perhaps if the installation hadn’t taken up to 30 minutes at a time (goodness knows what it was it was doing) I could have got back to Heroes an hour earlier.

After giving up, I re-installed VMware ESXi – an installation which, no kidding, took only 10 minutes end to end.

I have been planning a review of the virtualisation technologies, especially with respect to storage, clearly Hyper-V is going to make this a challenge.

Microsoft – you’re not on my Christmas card list this year (which they weren’t on in the first place as my wife writes all the cards in our house) – VMware welcome back.

NTFS Update

Chris M Evans — Mon, 24 Sep 2007 05:18:00 +0000

I did some more work on my NTFS issue on Friday. As previously mentioned, I was seeing NTFS filesystems with large levels of fragmentation even after drives were compressed.

The answer turns out to be quite simple; Windows doesn’t consolidate the free space blocks which accumulate as files are created and deleted. So, as a test I started with a blank 10GB volume and created a large file on it. Sure enough the allocation occurs in a small (2 or 3) number of extents. I then deleted the large file and created 10,000 small (5K) files and deleted those too. I then re-created the large file, which immediately was allocated in 100′s of small fragments and needed defragmentation immediately. The large file was created using the freespace blocks freed up from the small files.

What’s not clear from the standard fragmentation tool provided with Windows is that the free space created by the deletion of files is added to a chain of free space blocks. These free space blocks are never consolidated even if they are contiguous (i.e. as in this instance where I deleted all the files on the disk). This means even if you *delete* everything on a volume, then the free space is still fragmented and files will be created with instant fragmentation. The other thing to note is that the standard Windows defragmenter doesn’t attempt to consolidate those segments when a drive is defragmented, it simply ensures that files are re-allocated contiguously. It also doesn’t report that fact either.

I’m currently downloading Diskeeper, which allegedly does consolidate free space. I’m going to trial this and see how it affects my fragmentation problem.

Incidentally, I used one of Sysinternals’ free tools to look at the map of my test drive. Sysinternals were bought by Microsoft in the summer of 2006, however you can find their free tools here. I used Diskview to give me a map of the drive and understand what was happening as I created and deleted files. What I would like, however is a tool which displays the status of free space fragments. I haven’t found one of those yet.

So, now I have an answer, I just have to determine whether I think fragmentation causes any kind of performance issue on SAN-presented disks!