VCB – VMware Consolidated Backup 是  VI3 时代推出的针对虚拟机备份的一个组件，目前也适用与 vSphere 4.0 的备份，可以和其他备份软件相结合，实现 Lan-Free 和 Off-Host 的备份，和新的虚拟化环境相适应，与传统的 Backup Agent 方式的备份相比，不需要在每一台 Client 上安装 Agent 了，备份时数据流不通过 VM 和 ESX Host，减少了备份对应用的影响。

但是 VCB 的缺点是：
1. 备份时产生的 Snapshot会出现各种各样的问题，如 Snapshot 创建失败，Snapshot 删除失败，某些应用程序不支持 Snapshot 在其存续期间应用会产生故障；
2. 需要一台 VCB Proxy，安装 VCB 组件，以 NetBackup 为例，一般推荐安装在 NBU Media Server 上；
3. VCB 备份需要一个大的磁盘空间，用于放置虚拟机的快照，特别是进行 Full VM 的备份时，如果同时发起多个备份，需要考虑这个 staging disk 的空间一定要足够大，不然会出现 156 错误。

随着 vSphere 的推出，引出了 VMware vStorage API 的概念，可以替换 VCB。相比 VCB，VMware vStorage API 具有如下优点：
1. 不再需要 VCB Proxy 的角色，备份服务器可以支持从存储上 ESX Host 上看到 Datastore 中备份虚拟机；
2. 不再需要一个磁盘空间用作备份时的 staging disk；
3. 提供了 changed block tracking 功能，可以实现 block 级别的差别变化，大大缩短 image-level 增量备份的时间。

vStorage API 的限制：
1. ESX Host 必须是 4.0 以上版本 (也有一种说法是支持 ESX 3.5，但未经官方证实)；
2. VM 的硬件版本必须是 7 以上；
3. 至少目前看来，支持的厂商还比较少，只有新兴的如 Veeam 等厂商的备份产品支持，NetBackup 要等到 7.0 版本才会支持，而 NetBackup 7 目前还没有正式发布。

注：有一种说法［http://www.vnotion.com/?p=181］是 vStorage 支持 ESX 3.5，只是不具备 changed block tracking 等新功能，这个功能在进行增量备份的时候还是很有用的。

名词解释:
Changed Block Tracking – CBT is a new feature in vSphere that can keep track of the blocks of a virtual disk that have changed since a certain point in time. This is extremely useful for backup and replication applications that can use this information to greatly improve incremental backup and replication times. Without CBT these applications have to figure out changed blocks on their own so being able to get this information for free using the vStorage advanced programming interfaces is extremely valuable to them.

内容提要：

This document compares the performance of 4GbE FC, 1GbE and 10GbE iSCSI, and 1GbE and 10GbE NFS protocols using both VMware® vSphere™ 4.0 and ESX 3.5 on NetApp® storage systems. This document seeks to compare the individual protocol performance and CPU utilization at varying workloads.

一些测试结果：

在云计算方面，觉得 VMware 似乎慢了半拍，虽然 2009 年 9 月份随着 vSphere 4.0 的发布，提出了 vSphere 是业界第一款云操作系统，但是真正使用 vSphere 作为商用云计算平台的公司目前都还标明了“This service is currently in limited beta”（http://www.vmware.com/appliances/services/vcloud-express.html），目前还达不到 Amazon 使用 Xen 的成熟程度。

三种常见的云计算服务及其服务提供商：
   * Software-as-a-Service (SaaS)
     SalesForce CRM
     Google Apps
   * Platform-as-a-Service (PaaS)
     Google App Engine
     Microsoft Azure
   * Infrastructure-as-a-Service (IaaS)
     Amazon EC2
     The Rackspace Cloud

有句话很是认同：
If you want to be a SaaS provider then you may want build on top of a PaaS cloud.
If you want to be a PaaS provider then you may want to build on top of a IaaS cloud.
If you want to be a IaaS provider than you may want to build on top of virtualization.

嗯，我的观点是：虚拟化和存储是云计算的基础。

(There is another easy way to get the WWN of any HBA card vendor, just install NetApp Host Utilities and run the HBA Info in Start menu/All Programmes/NetApp/Windows Host Utilities/. Added at Jan. 13 2010 by xuming)

And if you bought the HP x86 PC server and have set up the server with the HP SmartStart or have installed HP System Tools on the server, there is a easy way to get the WWN number.

Just open the https://servername:2381 in your favourite web browser, follow the instructions below and you can get the WWN in easy way.

The first public comparison between the two blade systems comes from Steve Kaplan, Vice President Data Center Virtualization Practice at INX.

His technical analysis is well worth a read.  

And here is his storage predictions for 2010 and the year beyond

Storage Predictions for 2010 and Beyond

I’ll start with some easy predictions this time around. 

• FCoE will become available end-to-end, with major storage vendors supporting FCoE interfaces by the end of 2010. This should be an easy prediction, as the market is demanding FCoE given the potential cost and cabling savings. It takes longer for the design integration and testing of storage controllers, so it is no surprise that this takes longer than server or interconnect changes.
• PCIe 3.0 will make it to market, with availability in blades first. This is almost a given at this point.
• Multiple storage and server vendors will address the end-to-end data integrity problem. Now the predictions are getting tougher. There is definitely a market need given the documented problem of mis-corrected or undetected errors in the data path, and I believe that vendors will fill this market need in 2010. This will be the only major change in file system technology and the first major change in a long time.
• There will be market consolidation in the flash solid state drive (SSD) market in 2010. The number of vendors in the market is just too large for the size of the market. Some companies will either merge, get bought out, or disappear. The market for flash disk drives is only so big and it cannot support the large number of companies in the market even with the growth of the technology. And STEC (NASDAQ: STEC) will finally get some competition in the enterprise SSD market from the likes of Pliant and Seagate (NASDAQ: STX).
• Flash SSD usage will increase, with multiple RAID vendors and multiple controller card vendors providing better support, which means higher bandwidth and more IOPS in 2010.
• 10 Gigabit Ethernet will become the standard connectivity for almost all systems. Higher-end home PCs from Dell, HP and others will support this technology. Home routers from multiple vendors will have this support, likely before the end of the year (see Enterprise Technologies Will Change the Consumer PC Market).
• NFSv4.1 (pNFS) will enter the market with products from multiple vendors in 2010.
• 40 and 100 GbE will continue their march to product availability, with the potential for some interconnect between switches available in 2010, but with certain availability in 2011. For 40 GbE to be viable for the host side, dual port, will require PCIe 3.0 with at least 16 lanes, and at that PCIe 3.0 provides only 16 GB/sec of bandwidth, while 20 GB/sec is needed for full rate, full duplex operation. PCIe 3.0 is a must for host side connectivity.
• Last but not least: By the end of 2011, the cloud hype that you hear today will be greatly diminished. Clouds are good for some things, but just like the storage service providers and application server providers of the late 1990s or grid computing in the early part of this decade, clouds will meet a similar fate. SSPs and ASPs are providing services for some applications, but they are not going to solve all problems for all enterprises, as there is just not enough network bandwidth, the latencies for some applications are too high, and the security problem end-to-end has not be solved in a standard way (see Why Cloud Storage Use Could Be Limited in Enterprises). Besides, does anyone really see enterprises giving up control of their most critical data? I sure don’t.

In some perspective, it is more comparable to FCoE (Fiber Channel over Ethernet) than iSCSI. It export block devices (SATA HARD DISKS) over the network with a very high throughput when coupled with a quality Ethernet switch. A qaulity Ethernet switch can maximize throughput and minimize collisions through integrity checking and packet ordering.

In a typically implementation of AoE, you will need some dual-port Gig-E cards, a Gig-Ethernet switch and some disks.

#####
# Comparison of AoE vs iSCSI
################################

These are the following advantages of AoE over iSCSI

    * AoE is cheap and simpler software stack. The advantage of AoE is that you don’t have the overhead of translating ATA to SCSI then back to ATA if you are using ATA drives. So there is a performance pickup.
    * Server processing load for iSCSI is much higher than AoE for equivalent throughput. AoE can spare processing cycles. iSCSI requires TCP/IP and its requisite complexity.
    * AoE is not a routable protocol. Therefore it provides you inherent security.
    * AoE Ethernet frames are passed by standard switches.
    * AoE and iSCSI both have initiator support for Windows and Linux.

Disadvantages of AoE over iSCSI

    * If you need features such as encryption, routability and user-based access in the storage protocol, iSCSI is a better choice.
    * AoE is not much suitable for critical enterprise applications. AoE is not as scalable as iSCSI or Fiber Channel when you consider location i.e., with Fiber Channel and iSCSI, you can scale your storage throughout. This is primarily due to the inability of AoE to route AoE traffic.
    * ATA disks are not as reliable as their SCSI counterparts.

推荐阅读 ZFS 最佳实践指南：http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide

Before you can configure iSCSI storage, you must create a VMkernel port to handle iSCSI networking and a service console connection to the iSCSI network.

To create a VMkernel port for software iSCSI

1. Log into the VMware VI Client, and select the server from the inventory panel.
   The hardware configuration page for this server appears.
2. Click the Configuration tab, and click Networking.
3. Click the Add Networking link.
4. Select VMkernel and click Next.
   This lets you connect the VMkernel, which runs services for iSCSI storage, to the physical network.
   The Network Access page appears.

5. Select the vSwitch you want to use or the Create a virtual switch radio button.
6. Select the check boxes for the network adapters your vSwitch will use.
   
   Your choices appear in the Preview pane.
   Select adapters for each vSwitch so that virtual machines or other services that connect through the adapter can reach the correct Ethernet segment. If no adapters appear under Create a new virtual switch, this means that all the network adapters in the system are being used by existing vSwitches.

7. Click Next.
   The Connection Settings page appears.
8. Under Port Group Properties, select or enter a network label and a VLAN ID.
   • Network Label — A name that identifies the port group that you are creating. This is the label that you specify when configuring a virtual adapter to be attached to this port group, when configuring iSCSI storage.
   • VLAN ID — Identifies the VLAN that the port group’s network traffic will use.
     

   • Under IP Settings, click Edit to set the VMkernel Default Gateway for iSCSI.

     The DNS and Routing Configuration dialog box appears. Under the DNS Configuration tab, the name of the host is entered into the name field by default. The DNS server addresses that were specified during installation are also preselected as is the domain.
     
     Under the Routing tab, the service console and the VMkernel each need their own gateway information. A gateway is needed for connectivity to machines not on the same IP subnet as the service console or VMkernel.
     

     Note

     Make sure that you set a default gateway for the port that you created. You must use a valid static IP address to configure the VMkernel stack.

9. Click OK to save your changes, and close the DNS and Routing Configuration dialog box.
10. Click Next.
11. Use the Back button to make any changes.
12. Review your changes on the Ready to Complete page and click Finish.

After you create a VMkernel port for iSCSI, you must create a service console connection on the same vSwitch as the VMkernel port.

To configure a service console connection for software iSCSI storage

1. Log into the VMware VI Client and select the server from the inventory panel.
   The hardware configuration page for this server appears.
2. Click the Configuration tab, and click Networking.
3. On the right side of the screen, click Properties for vSwitch associated with the VMkernel port you just created.
4. On the Ports tab, click Add.
   The Add Network Wizard appears.
   

5. As a connection type, select Service Console and click Next.
   The Connection Settings screen appears.

6. Under Port Group Properties, enter a network label that identifies the port group that you are creating.
   
   Newer ports and port groups appear at the top of the vSwitch diagram.

7. Enter the IP Address and Subnet Mask, or select the DHCP option Obtain IP setting automatically for the IP address and subnet mask.
8. Click the Edit button to set the Service Console Default Gateway.
9. Click Next.

   The Ready to Complete screen appears.
   

10. After you have determined that the vSwitch is configured correctly, click Finish.

After you create a VMkernel port and service console connection, you are able to enable and configure software iSCSI storage.