Friday, March 28, 2008

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:

Silver 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 Saldich

VP Product Marketing & Alliances


  • 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, and my cell phone is +1 650 888 4032.

WAN war breaks out over changed file formats in AutoCAD MEP

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...
Bryan Betts, Techworld

A 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.

Monday, March 17, 2008

How to best place Addenda, Alternates, or As-Builts within the project?

How you organize these items would largely depend on your internal processes and workflow. One solution would be to draw the alternates as regular constructs in Project Navigator and then create special views for them.

If you want to present completely different plans/elevations to represent Alternates, you could use divisions in Project Navigator to represent them; when generating the view, you just need to include the appropriate division into the view.

In some cases you might also consider copying the project in Project Navigator and put the Alternates into the copied project. If you copy a project, however, you have two different file sets to maintain; the copied project does not retain any links to the original one.

Friday, March 14, 2008

Project Navigator performing slowly in AutoCAD MEP

Some activities in Project Navigator, such as loading xrefs, take what seems like a long time. This is normal. These processes need to run their course before other activities can be initiated.

I was recently working with a client who is creating a large hospitol project using AutoCAD Architecture and AutoCAD MEP and project navigator. I noticed how long it was taking to open constructs, views and sheets and so I looked for some info that could help them be more productive and came across some tips to help improve performance of their project navigator.

The specific activity of dragging a view to a sheet actually involves several background processes, including loading all the files in nested external references, updating project database files, managing layers for viewports, scaling geometry, and coordinating data fields and labels.

For your network environment, follow the guidelines below:

  1. To rule out any potential problems with your network environment, temporarily copy the project files to a local workstation and perform the same operations with Project Navigator. Compare the speed in both environments to determine if the problem is directly related to network speed.
  2. Use a Windows operating system on your server. AutoCAD MEP only supports a Windows networking environment. If you are using a Novell or UNIX server, you will need to install the Windows Client for these operating systems. However, due to the permission restrictions on these operating systems, the performance of Project Navigator can be dramatically affected.
  3. Install the most recent service packs and patches for the version of Windows installed on your server.
  4. Check for the presence of antivirus and spyware applications on your system. These applications have features, such as Symantec's Auto-Protect functionality, that constantly monitor the files on your computer or server. This type of application can slow performance down because files are being scanned while they are being used. If you are using this type of virus protection, try disabling it to see if performance is affected. You should disable this feature on the server as well. If you want to leave this feature enabled, you can set up exclusions for the files and folders you use with your projects.

For your workstation, follow these guidelines:

  1. Install the most recent service packs and patches for the version of Windows installed on your workstation.
  2. Disable Digital Signatures in AutoCAD MEP: In the Registry Editor, look for the following key: [HKEY_CLASSES_ROOT\CLSID\{36A21736-36C2-4C11-8ACB-D4136F2B57BD}\InProcServer32] Delete the content of the Value Data field for the Default item.
  3. If you have custom hatch patterns, make sure that they are not loaded as part of the or files. Any custom pattern should be saved as a separate PAT file in the support directory location.

For your project files, follow these guidelines:

  1. When working with Project Navigator, all users should be using the same version of AutoCAD MEP. Every new version of AutoCAD MEP introduces additional information saved on the project files and that can create conflicts and slowdowns if different versions are used to read the same files.
  2. If you are using old template files, cut the entire contents and paste them into an updated AutoCAD MEP template.
  3. Purge unused block definitions take up a lot of file space in all drawings.
  4. In all drawings, including the template drawings used by Project Navigator, the value for the variables should be set to the predefined value: INDEXCTL = 2 (Spatial indexes are created) XLOADCTL = 2 (Enabled with Copy. This enables demand loading, but uses a copy of the referenced drawing, so others can edit the original drawing.)
  5. Manage the temporary files that are created as part of the “Enabled with Copy” demand load strategy built into Project Navigator. These files remain after a system failure or an aborted Project Navigator activity. Deleting the AC$ files in the Temp folder can reduce the time required to open most drawing files and significantly improve system performance.
  6. Minimize Multiple Sessions. Launching multiple or concurrent sessions of AutoCAD MEP, AutoCAD Architecture, AutoCAD, or Revit MEP dramatically reduces system performance and may possibly affect the overall stability of the system. Avoid this practice and adopt other work methods. If you cannot avoid multiple sessions, consider using your most capable workstations in these situations.
  7. Before dragging views into sheets, temporarily unload external references from the view drawings. Drawings with attached xrefs will reproduce that xref. This can lead to duplicate or circular xrefs and confusion as to what should actually be in the drawing. This can tax workstation resources and affect performance.
  8. Check for the presence of the following blocks in all your drawings, and delete them: AVE_GLOBAL, AVE_RENDER, RM_SBD
  9. Detach any AutoCAD CAD Standards associated with the individual drawings. This can be done on the CAD Manager menu, under AutoCAD CAD Standards.
  10. Change the FIELDEVAL variable to [2], so field values are only updated when the drawing is saved.

Wednesday, March 12, 2008

Reduced write performance for Riverbed WAN links when working with AutoCAD MEP 2007 DWG files

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.

Monday, March 10, 2008

Civil 3D Object Enabler Breaks the Add Pipe/Duct Tool in AutoCAD MEP

There is an issue with AutoCAD MEP where you cannot draw more than one segment of pipe or duct at a time. When you are prompted for starting point, and ending point of the first segment, the command exits without allowing for additional segments.

The Civil 3D Object Enabler breaks the pipe/duct add mechanism. The Autodesk development team has tentatively scheduled to deliver a fix in the next update to the Civil 3D Object Enabler, available in approximately two to four months. Please note their quality assurance teams may need to reschedule some fixes. Please rely on the timeline information as a guideline only and not a guarantee.

If this is happening to you, you only have two options as of now. Uninstall the Civil 3D Object Enabler, or continue with the add duct/pipe tool ending after each segment is added.