Wan Accelerators

Autodesk finally released a hotfix to improve the performance of saving to 2007 DWG format when running in a WAN Acceleration environment. The problem was an Autodesk problem, and not anything related to any particular Wan Accelerator as some people have thought. This is a Hotfix posted by Autodesk that you can also view from the following links...

2009 Wan Acceleration Hotfix link
2008 Wan Acceleration Hotfix link
2007 Wan Acceleration Hotfix link

Description of Problem
WAN acceleration technology typically relies on data-deduplication as a significant part of accelerating data transfer. The 2007 DWG format is written to disk with a type of error-checking that has the side-effect of nearly every byte of the file changing during full-save, even if little was changed. WAN accelerators fail to deduplicate the 2007 DWG data and must transfer nearly all bytes in the 2007 DWG file. This results in a slow-down during full-save when working over a slow WAN.

This hotfix will make a small change in the way the 2007 format DWG files are written to disk such that WAN acceleration hardware will be better able to deduplicate the 2007 DWG data; this will provide some performance gains for SAVE operations when users are saving across a WAN acceleration environment. The resulting 2007 DWG file will be readable whether or not others have this hotfix, but to achieve the best performance everyone working on the same DWG should install this hotfix.

After intalling the hotfix, you must set the Windows environment variable, ACADCOMPRESSIONMODE to 1 for it to have effect.

Note: For AutoCAD, you can often get performance gains in QSAVE operations by setting the ISAVEPERCENT system variable to 100. Using a value of 100 will maximize the chance that a QSAVE operation will use incremental-save rather than full-save. (WAN accelerator technology is able to show good performance in deduplication of 2007 DWG format files when incremental save takes place.)

Applicable Products
AutoCAD 2009
AutoCAD LT 2009
AutoCAD Architecture 2009
AutoCAD Civil 3D 2009
AutoCAD Electrical 2009
AutoCAD Land Desktop 2009
AutoCAD Map3D 2009
AutoCAD Mechanical 2009
AutoCAD MEP 2009
AutoCAD P&ID 2009
AutoCAD Raster Design 2009
AutoCAD Revit Architecture Suite 2009 (1)
AutoCAD Revit MEP Suite 2009 (2)
AutoCAD Revit Structure Suite 2009 (1)
Autodesk Inventor™ Professional 2009 (3)
Autodesk Inventor Suite 2009 (3)

(1) Apply this hotfix only if the installation includes AutoCAD 2009.
(2) Apply this hotfix only if the installation includes AutoCAD MEP 2009.
(3) Apply this hotfix only if the installation includes AutoCAD Mechanical 2009 or AutoCAD Mechanical Desktop® 2009.

Installation Instructions

To Install the WAN Acceleration Hotfix
You must have administrative privileges on your Microsoft® Windows® operating system to complete the installation process.

This installation requires you to replace the following files:

• acdb17.dll
• AcSignCore16.dll

After you replace these files, you must restart your system in order for this hotfix to take effect.

NOTE: Only apply this hotfix after you have installed an AutoCAD 2009-based product. This installation requires you to modify an installed product, which may cause Windows security warnings to display. For all Windows security warnings that display during installation, click Continue.

To Replace the acdb17.dll File

1. Close all software applications.
2. Navigate to your product installation folder; for example C:\Program Files\AutoCAD 2009.
3. In the product installation folder, right-click the acdb17.dll file and select Properties.
4. Click the Version tab and confirm the file version.
5. If the file version is 17.2.56.0, 17.2.111.0, or 17.2.112.0, proceed with this installation.
6. If the file version is greater than 17.2.112.1, do not install this hotfix.
7. Rename the affected original file.
8. In the product installation folder, right-click the acdb17.dll file and rename it acdb17.bak.
9. Based on the product you have installed and its version of the acdb17.dll file, double click the appropriate file.
10. For AutoCAD 2009-based products with the acdb17.dll file version 17.2.56.0
11. Based on the version of your product, double-click WAN_Accelerator_Hotfix_2009_32bit.zip or WAN_Accelerator_Hotfix_2009_64bit.zip.
12. For AutoCAD 2009 Update 1 with the acdb17.dll file version 17.2.111.0 or 17.2.112.0
13. Based on the version of your product, double-click WAN_Accelerator_Hotfix_2009_Update_1_32bit.zip or WAN_Accelerator_Hotfix_2009_Update_1_64bit.zip.
14. Extract acdb17.dll file to the product installation folder; for example C:\Program Files\AutoCAD 2009. NOTE: Keep the zip file that you used in step 6 open. Without opening other software applications, immediately proceed to the procedure below .

To Replace the AcSignCore16.dll File

1. Navigate to your Autodesk Shared folder; for example: C:\Program Files\Common Files\Autodesk Shared.
2. In Autodesk Shared folder, right-click the AcSignCore16.dll file and select Properties.
3. Click the Version tab and confirm the file version.
4. If the file version is 17.2.56.0 proceed with this installation.
5. If the file version is greater than 17.2.112.1, do not install this hotfix.
6. Rename the affected original file
7. In the Autodesk Shared folder, right click the AcSignCore16.dll file and rename it AcSignCore16.bak.
8. Double-click the zip file you used when you replaced the acdb17.dll file. See To Replace the acdb17.dll File, Step 6.
9. Extract the AcSignCore16.dll file to the Autodesk Shared folder; for example: C:\Program Files\Common Files\Autodesk Shared.
10. Restart your system.

To set the ACADCOMPRESSIONMODE environment variable

On Windows XP

1. Right-click My Computer, and then click Properties.
2. Click the Advanced tab.
3. Click Environment variables.
4. Click New to add a new system variable name and value.
5. Set the Variable name to ACADCOMPRESSIONMODE
6. Set the Variable value to 1
7. Click OK until you return to the desktop

On Windows Vista

1. Right-click My Computer, and then click Properties.
2. Right-click My Computer, and then click Properties.
3. Click the Advanced system settings link.
4. Click Environment variables.
5. Click New to add a new system variable name and value.
6. Set the Variable name to ACADCOMPRESSIONMODE
7. Set the Variable value to 1
8. Click OK until you return to the desktop

To Uninstall the WAN Acceleration Hotfix

1. In the product installation folder
2. Delete the acdb17. dll file that you downloaded.
3. Restore the file you renamed to the original name. See To Replace the acdb17.dll File, Step 5.
4. In the Autodesk Shared folder
5. Rename the AcSignCore16.dll file to AcSignCore16.dll.hotfix.
6. Restore the file you renamed to the original name. See To Replace the AcSignCore16.dll File, Step 4.
7. Restart your system.

For more information about this issue, I have previous posts around it
WAN war breaks out over changed file formats in AutoCAD MEP
Reduced write performance for Riverbed WAN links when working with AutoCAD MEP 2007 DWG files
WAN Accelerators Part II

I recieved comment from Alan Saldich, the VP of Product marketing for Riverbed and below is his message. He told me basically that this is not a Riverbed issue, but an Autodesk issue, and that all WDS solutions are affected by the file format change. Here is his letter.I’m the VP of product marketing for Riverbed, and I wrote a lengthy post yesterday on this topic, which can be viewed here:http://www.wdsforum.org/forum/index.php?showtopic=183Silver Peak has admitted (in a call earlier this week with the TechTarget reporter who wrote that article) that the issue with the AutoCAD 2007 / 2008 .dwg file format is *not* specific to Riverbed and *does* affect all products that use deduplication in their solutions, including their own. The only way to determine the degree to which any particular WDS solution is affected by the file format is to do your own testing. Remember, the problem is most pronounced with the ISAVEPERCENT (Incremental Save Percentage) set to zero, which forces a complete save, and which causes all the bytes to be scrambled. Using a non-zero value for that setting (like the default value of 50) reduces , but does not entirely eliminate, the impact of the new file format on WDS solutions.Unfortunately this is not an issue that can be solved by Riverbed or any other WDS solution provider - it was caused (inadvertently) by the way Autodesk decided to change their file format, including scrambling the bytes on every complete save. Any product that tries to find duplicate data will be affected, possibly to a varying degree, but there is no doubt there is an adverse effect.Alan SaldichVP Product Marketing & AlliancesRiverbed

• I'd like to post my own response to this as Riverbed's VP of Product Marketing and Alliances. I know this is a frustrating issue for our customers who rely on us and on Autodesk, and that's why we did the webcast in the first place a few weeks ago - to explain the issue as best we could. I have personally been working on this issue extensively for the last few months, and especially in the last few weeks. Let me make a few points and give you all an update.We have worked with Autodesk directly on this and we know what causes the problem, and Autodesk agrees with us. It is definitely not specific to Riverbed. Let me be clear: There is absolutely no dispute about that. Autodesk has had developers looking into the issue with their new file format to see if there's something that can be done. Unfortunately as of this moment there is no immediate fix. The problem is caused by a rescrambling of the bytes in Autocad 2007 / 2008 files upon a complete save, and that causes "cold" performance on writes. Reading files across the WANReads are generally fast because if the file in question has been written across the WAN before, then the bytes have not been re-scrambled and the read is fast, as usual. However, if you have a highly collaborative environment where someone in the other office could open and re-save the file, in that case the second read across the WAN could also be slow (because the bytes are again re-scrambled).If users are using other versions of AutoCAD or Civil 3D that don't rely on the newer file format, then they are not affected. The rescrambling is not compression nor encryption - it is an inadvertent byproduct of performance improvements that Autodesk made in an effort to make AutoCAD work better (nothing to do with WANs at all).The only option right now is to leave the Incremental Save Percentage (ISP) setting at its default setting of 50 - that works much better than forcing a complete save. There's some confusion here about whether a setting of 0 or 100 is the one that causes the complete save, and we're trying to clear that up (anyone know for sure?).Several of our competitors (Cisco and Silver Peak primarily) are trying to take advantage of this issue by claiming that it is somehow specific to Riverbed, and that is where a lot of the confusion and angst comes from. Silver Peak has probably been the most aggressive on this front. Unfortunately, they have been wrong about (1) how Riverbed is impacted by this and (2) claiming that they are not affected by the problem. Silver Peak has conceded (yesterday) that (1) this is not a Riverbed-specific problem, but rather it's caused by the way .dwg files are written in the new format, and (2) their products are also affected by it.If you read their claims carefully, and after talking with them it became more clear, their claims that they work well with AutoCAD 2007 / 2008 are couched in terms of average deduplication rates across a range of ISP settings (remember the only relevant use case here is a complete save, not incremental saves), across other Autodesk products like Revit (again, not relevant because Revit does not use .dwg files and is not affected by this issue), and by including other irrelevant operations like FTPing the same file over and over (again, not relevant because the files are not re-saved and therefore the bytes don't get scrambled again, so you get "warm" performance). Just to reiterate again... the problem occurs only when you do a complete save.Silver Peak still claim to be less affected - we'll see if that's true and by how much). The only way to document that will be through publicly available testing of both products under the exact same scenario. We are working on that through a customer who has their products and we will publish the results as soon as we can. We have already completed testing with Cisco's products and Blue Coat's and we have demonstrated the same problem affects their products in almost exactly the same way. As for our products being 'bricks', I'm very sorry you feel that way. If you are having problems, I would like to help you set up a support call to make sure there isn't some other issue like a duplex mismatch or other networking-related issue.We have literally hundreds of architecture, engineering and construction companies all over the world who rely on our products to accelerate AutoCAD, including most of the large multi-site firms in the US. Overall, as of December 31st, we had over 3,500 customers in virtually every industry and over 40,000 Steelhead appliances in use, so it's hard to believe that this is a systemic problem. If you or anyone else on this board would like to talk to me personally, I'd be happy to. My email is alan@riverbed.com, and my cell phone is +1 650 888 4032.

Article sent to me from a user. Thanks for the link. I summed up the article below. From the article, it sounds like Autodesk doesn't have a solution yet. I don't know much about the various WAN acceleration applications, but I thought I'd share these articles with you.It seemed like a good idea at the time...By Bryan Betts, TechworldA changed file format has sparked off a fierce war of words between users, WAN acceleration vendors and Autodesk, which significantly changed its DWG drawing file format in both the last two versions of AutoCAD. The result, is that WAN optimisation gear from the likes of Riverbed Networks - which has a strong user-base in CAD - is no longer able to accelerate file transfers over the WAN. Given that many CAD-using companies need to share drawings across multiple offices, that's a big problem. At issue is a new dynamic file format which deliberately makes a saved file look completely new, even if it is only an edited version of an existing file, says Riverbed VP Alan Saldich. That means block-level caching schemes can't do what they'd normally do, which is to send only the changes over the WAN. Format errors "To improve the speed of the application itself, they changed the file format so that every time you change the file, every bit gets scrambled," Saldich explains. "If you FTP the file twice or reopen it without saving, we can work on that."There's only two ways to solve it. One is for Autodesk to revert to the former file format, which seems unlikely. The other thing is they could tell us enough about the file format to undo it." Saldich explains.In the meantime, Saldich and Autodesk VP Guri Stark have issued a joint statement advising affected users to do one of two things: either revert to an earlier AutoCAD DWG file format; or adjust an AutoCAD setting called Incremental Save Percentage (ISP) to 50, which reduces the amount of data scrambling when a file is saved. Other WAN acceleration companies have used the issue to bash companies such as Riverbed for developing application-specific optimisation modules. However, Saldich claims it's nothing to do with those - he says they're just protocol optimisations to reduce the number of round trips, and they don't deal with file formats. He argues that it's one of the first symptoms of a bigger problem that is only just emerging now."It affects any product that relies on data de-duplication, including backup and replication," he says. "I truly think the AutoCAD team were unaware of this when they did the development work back in 2004, as data de-duplication wasn't common then. "The bigger story here is that de-duplication is a widely-used technology now, and software developers need to take account of that. We are 100 percent certain of the problem, and any vendor has the same issue, which is that you don't get to look at the data before it gets written to disk." Aaron claims Autodesk had its own reasons for formally testing his company's gear - it is a Silver Peak user, with some three dozen of its WAN optimisers around its organisation. Aaron acknowledges though that when Saldich argues that application developers need to be better aware of how their software will run over a WAN, he has a good point. "The more the software developers do to address this, the more we all benefit," he says.We asked Autodesk for its comments, but nearly two weeks later the company had still not found a spokesperson or offered any feedback.

In March 2006, Autodesk changed the DWG file format for AutoCAD 2007 to make it more compact and improve performance for AutoCAD users. Autodesk’s customers widely welcomed this change and almost all AutoCAD users have enjoyed improved performance.However, Autodesk and Riverbed have recently received reports that some customers using some WAN acceleration appliances, including Riverbed’s Steelhead appliances, have experienced noticeable reductions in write performance when working with files saved in the AutoCAD 2007 “DWG” format. One of the side effects of the DWG format changes is that when users perform a complete save from within AutoCAD (as opposed to an “incremental” save), virtually every byte of the file gets changed – even if zero changes were made to the file itself. The net effect is that writes that would normally affect only “warm” data are actually “cold”, due to the reordering of the data in the file.Users of Riverbed or other affected WAN acceleration solutions can implement the following immediate workarounds that improve write productivity.

1. Using a feature in AutoCAD called “Incremental Save Percentage” (ISP), and setting it to 50
2. Using a version of the DWG format other than the AutoCAD 2007 DWG format.

The performance and productivity of their customers is a key consideration for Autodesk and Riverbed. Both engineering teams are working together to devise workarounds and are examining potential longer-term solutions. Given Riverbed’s experience in WAN acceleration technology, our joint work may also provide solutions for customers of other WAN acceleration or deduplication technologies, who might be experiencing similar issues with write performance.