Windows 7 is faster than Windows XP in many ways, and one boost comes from a long-needed update to the SMB (Server Message Block) protocol—as long as you use compatible Windows Server editions. Here’s an overview of SMBv2 and what it means to companies deploying Windows 7.
In its new OS, Microsoft updated the aging SMB protocol components—known to some as CIFS – and in doing so, provided the means to make it far faster to perform file transfers and deal with multiuser software needs.
The big SMB and speed change came first to Windows Vista editions, but the speed difference wasn’t very dramatic. The reason is that SMB is about relationships, and compatible Windows Server editions are needed to get a perceptible speed increase. The client and server (or server device) needs to support SMBv2 to get any advantage. If a host is an SMBv1 device (as are most print servers, as an example), then there is no speed improvement because SMBv2 falls back to the SMBv1 for compatibility reasons. None of the speedy components are available in the relationship because conversations revert back to SMBv1 speeds unless both devices are SMBv2.
And therein lies a strange part about SMBv2. Some devices on a network will be really fast because they’re sped up by SMBv2 relationships, while another server or shared storage device (running SMBv1) might appear as though it’s comparatively asleep. For the time being, most non-Microsoft Windows server devices don’t support SMBv2, although print servers, storage servers, and other non-Windows devices (especially those devices using Linux) may get an update in 2010 that will support SMBv2 functionality (called SAMBAv4) and things return to their speedy SMBv2 pace.
Along with the initial edition of the update came a problem, as it was soon found that the SMBv2 had some potential security problems. These are now fixed by updates (and described in this Microsoft Tech Bulletin: MS09-050). If you have automatic updates turned on, you’re already fixed. Don’t use SMBv2 without the updates, as exploits that can simply blue-screen your machine are easy to accomplish.
Why is SMBv2 faster? There are many reasons and no one disagrees that the v1 to v2 updates were needed. The history of SMB can also be found by searching for CIFS, or the Common Internet File System, a method of communicating files, their contents, and file states between machines. There’s more to SMB, described below.
The original SMB protocol has had numerous fixes over its decade and a half life, but none so radical as in SMBv2. Efficiency was brought by cutting down the number of back-and-forth maintenance packets between hosts and client computer, as well as increasing the buffer sizes used. Today, Windows 7 uses still another update, SMBv2.1, and more can be expected.
SMB is an underlying convention and protocol suite that represents access, resources, and underlying relationships between two or more computers or other network-shared devices, and manages interchanges between network devices. In practice, users don’t see the plumbing, rather they see the network shared resources represented by the plumbing. The devices are often computers (like servers and workstations) but can also be printers, file repositories (like the DFS/Distributed File System), or network shares.
Most Windows users know SMB most simply as their “Network Neighborhood.” When they can’t logon or authenticate to a resource listed in their neighborhood, it’s because of another part of the SMB protocol that does that.
Also, inter-process components allow network applications to join to local resources. In older SMB versions, there were over 100 commands to link, chat, and communicate between application requests and the communications processing of those requests. These are boiled down dramatically in SMBv2, and the reduction in the commands and their chattiness–something users almost never see–improves speed and efficiency.
Move importantly, SMB relationships built between a computer and network resources are tougher to tear down when normal events occur, such as a WiFi or other network link becoming unavailable for a moment or so. The ability to sustain communications over intermittent or contentious links (think of overly-used access points at coffee shops) means that SMBv2 links across a VPN link from a computer to a Windows Server 2008 server won’t need surprising re-authentication, and that file downloads can withstand temporary interruptions without having to restart the download from scratch. Connection persistence helps get the job down more quickly with SMBv2 as well.
Expectations and Gotchas
If your organization has implemented SMBv2, you’ll see the speed in quicker downloads, easier and faster access to server shares, and applications like MS Outlook retrieves mail faster than ever before. When the big downshift to SMBv1-based occurs, you’ll notice the difference after SMBv2—especially during downloads.
But all of this requires that both computers and servers are compatible with SMBv2. While Microsoft’s Windows 2008+ servers have it, predecessor editions do not. Most Linux servers (and Apple clients and servers) don’t have it yet, and that means that network attached storage (NAS) devices that use BSD or Linux have no speed benefit until a stable SAMBA 4 version arrives for NAS devices that use SAMBA (which is an SMB emulator for non-Microsoft systems).
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