A Gurus Guide To Macintosh Performance Acceleration

Photoshop Acceleration Strategies
by Boots(boots@macgurus.com)



The famous "Liquid Sky" Photoshop splash screen.... you can access it by selecting ’About Photoshop’ from the Photoshop menu in the menubar while pressing the command key.


  In any discussion of performance acceleration, it is important to remember Photoshop user requirements vary widely. While single-user and small workgroup environments will benefit from most of the ideas outlined below, a smaller percentage of specialists can also justify the added expense of the faster RAID arrays for Photoshop’s ’scratch disk’. Certainly a cost/benefit assessment of any potential hardware upgrade should be tailored to the real-world requirements of your particular workflow. A large segment of Photoshop users may realize the most benefit by installing additional RAM as the only hardware upgrade. If your workflow constantly maintains an Efficiency reading of 100%, a fast RAID array may not be cost-effective. Macgurus recommends a well-thought out approach to hardware acceleration based on real-world necessity, rather than ’a need for speed’ for its own sake.

  Today’s Photoshop users take advantage of every bit of muscle their Mac’s can muster. Hi-bit workflows, complex filter operations, huge, many-layered files, and situations that require multiple applications to be in use simultaneously- can quickly push your Mac’s capabilities to the extreme. To begin with, please consider Adobe’s official recommendations for optimizing Photoshop performance.

  Macgurus has compiled a number of additional tips and suggestions to help you squeeze every last bit of power from your existing setup, and some graphic comparisons to illustrate the performance impact of various system configurations. Some of these tips are applicable to overall system health, speed, and efficiency while some are particular to Photoshop. Because of the advanced nature of certain configurations, appropriate care and caution should be used before you perform any alteration to your existing setup. We’d like to stress once again the importance of maintaining current, regular, and reliable backups of your precious Data. So sit back, take a sip, peruse freely, and be glad you bought a Mac!

TopTenTips: (well, 12 actually!)

1. Maintain a "lean ’n mean" approach when installing the Operating System and Applications. Keep disk clutter to a minimum by eliminating unused applications and language localizations, extra printer drivers, unnecessary extensions or plugins, and unused or rarely used fonts. This can help to keep your system and data files closer to the faster, outer area of your hard drives for faster performance, and minimizes the odds of encountering software conflicts.
   
   
2. Install and run the latest version of Photoshop on the fastest possible Mac, preferably a dual-processor machine. Adobe has indicated that while certain filters are slower in Photoshop CS, overall performance of Photoshop CS is actually about 7% faster than Photoshop 7. If your G4 Mac needs more power, consider a Dual Processor upgrade. According to Adobe, "All Photoshop features are faster on a multiprocessor system, and some features are much faster."
   
   
3. Carefully plan the optimum file sizes and Image Mode for your particular output requirements. Working on files that are unnecessarily large can slow down operations dramatically and quickly use up disk space. This is especially important for users working in 16 bits per channel for all or part of their workflows. Preserve disk space by saving in Photoshop format. If you work in TIFF format and can afford the extra disk space required, save uncompressed files- they will open and save more quickly.
   
   
4. Take advantage of Photoshop’s incredible automation and scripting capability. With a little organization and planning, many repetitive daily tasks can be reduced to a keystroke or a droplet.
   
   
5. Provide Photoshop with as much RAM as possible for the best performance. By doing this, you allow Photoshop to load large images entirely in RAM without resorting to the slower ’virtual memory’ process, which uses the hard drive as temporary storage for memory. And you’ll ’hit the scratch disk’ much less frequently. Photoshop needs a RAM allocation of at least 3 to 5 times the size of the file being worked on, in order to stay at a 100% Efficiency reading- or in other words, to keep the file completely in memory. Currently, Photoshop 7 and Photoshop CS are "officially" limited to addressing no more than 2 GB of RAM. In actual practice, a "100% Allocation" of RAM to Photoshop 7.01 is around 1800 MB on systems with 2.5 or more GB of RAM installed. In Mac OS X, the maximum amount of RAM available to Photoshop on a given machine will vary according to the quantity and nature of any startup items, running background processes, and other open applications.
   An important thing to remember about OS X: the system will always reserve a minimum amount memory for itself. Though it can certainly run on less, we recommend the operating system should not be ’starved’ below a minimum of 512MB of RAM for smooth and efficient operations. If the operating system is regularly forced to page out to disk (swapfiles) because of insufficient available RAM, any gains in Photoshop performance from a large RAM allocation will be offset.
   
   It should also be noted there are differences in recommended memory use between Photoshop versions 7 and Photoshop CS. Adobe has specifically stated, that for Photoshop CS, "If you have 4 GB or more of RAM, set the Maximum Used By Photoshop in the Memory Usage section of the Memory & Image Cache preferences to 70%. This amount ensures that Photoshop uses as much of the first 2 GB of RAM as possible, while reserving enough RAM for other applications."
   As far as we can tell, a 100% RAM allocation to Photoshop 7.0.1 does not inhibit its performance- provided sufficient RAM is available for the OS.
   
   For Photoshop on PowerMac G5’s, we recommend a minimum of 2.5GB of RAM be installed in order to maximize Photoshop’s RAM allocation. This way, the operating system will not suffer under a "100%" or a "75%" allocation to Photoshop. Recent studies have shown that loading a G5 with 4GB of RAM provides about the maximum possible benefit. Beyond 4GB the cost/benefit ratio for Photoshop acceleration quickly deteriorates.
   
   Even a large RAM allocation in Photoshop can be used up quickly; extremely large files, multiple files and copies open, files with many layers and history states- all these situations can contribute to lowering Photoshop’s ’Efficiency’ reading below 100%- even on machines maxed out with RAM. When Efficiency regularly remains below 100%, add RAM first- then a fast scratch disk.
   Adding additional RAM to your machine is an excellent investment, as it tends to improve overall system performance across a wide range of applications- not just Photoshop.
   
   
6. Use a fast startup disk for the system and application files. Today’s 8MB cache ATA and SATA drives offer faster overall performance, loading and executing application code more quickly, and opening and saving files faster. The WD740 "Raptor" can be an excellent choice for instance, providing substantial all-around system performance improvement at a modest cost. Photoshop’s general performance improves with a faster startup disk.
   
   
7. Get a grip and start learning those Photoshop keyboard shortcuts! There is probably no better way to keep up with your newly-optimized and finely-tuned "muscle" Mac and Photoshop "beast", than to optimize your own ergonomic approach by minimizing unnecessary mouse movement. This is definitely worth the effort and will save you many minutes over the course of a day, and many, many hours during the life of your career. Enjoy!
   
   
8. Implement multi-channel storage acceleration for the Operating System and User/data files. By installing two fast 8MB cache ATA or SATA drives on separate internal busses, you provide your Mac with twice the available storage throughput. By separating the Operating System to one drive, and your User data to the other, a system-wide performance boost will result. Photoshop performance improves with faster saves to disk- even with a default scratch disk location of the startup disk. Combine this with an additional drive or striped RAID array on another independent bus exclusively for the scratch disk, and the fastest overall configuration is achieved.
   
   
9. Provide Photoshop with a dedicated scratch disk on a second hard drive or disk array. By "dedicated", we mean that the drive or volume is used only for the scratch disk and no other files. Every time you open Photoshop, the application automatically creates a large- and normally invisible- temporary file and writes it to the designated scratch disk, regardless of the image file size, or memory allocation settings. Even with History states and image cache levels at the minimum, and memory allocation and Efficiency at maximum, Photoshop still uses this temporary file- automatically accessing it and updating it as you make changes to the open image file.
   This scratch disk action is very sophisticated: if at all possible, Photoshop will make changes to the temporary file only during idle time, when the user is not performing any operations. If you start to make changes to the image while the scratch disk is updating, the process is immediately put on hold until you complete your changes, after which the updating resumes until complete, or is interrupted again.
   
   
   
   The ever-present Photoshop temporary file, also known as the ’scratch file’ or ’scratch disk’. Normally invisible, we’ve used the excellent system utility Cocktail to make the file visible in the finder. Note also the presence of Adobe ImageReady’s temporary file. IR uses a similar scratch disk mechanism- though not quite as sophisticated as Photoshop’s.
   
     When you first open Photoshop, the scratch file is roughly 25-50MB without any documents open. It grows quickly and varies according to image size. When you add history states, layers, saved selections, and alpha channels, the scratch file usually balloons to many times the size of the image file. In PS7, when the scratch file reaches 2 GB in size, a second scratch file is created. When that one reaches 2GB, a third is made- and so on. If you work in 16 bits per channel on large files, this can mean many scratch files- and having large areas of contiguous free space on the designated scratch disk volume becomes really important! For non-startup disk scratch disk volumes, a volume size of at least 4 GB is highly recommended, but typical scratch partition sizes are often much larger.
   
     If the designated scratch disk happens to be the startup disk containing the system, the Photoshop application, and the open Photoshop file, then the armature of the hard drive has to move back and forth more frequently and for relatively long distances to read and write these changes to disk. This is the default configuration, and depending on the speed and other characteristics of the hard drive, and available disk space on the startup disk, this can end up being the slowest possible arrangement.
   
     If you must run Photoshop with the scratch disk at the default location, maximum speed is maintained by keeping large amounts of free and unused space on the drive. If most of the files are on or near the fastest, outer portions of the drive, everything runs faster. Large areas of contiguous free space will promote ideal conditions where the scratch disk file is written in contiguous chunks, thereby offering the fastest reads of that file. But this is the high-maintenance alternative and requires vigilance and/or a really large drive. Squeeze Photoshop’s scratch disk space and she tanks.
   
     By providing Photoshop with an additional hard drive or striped RAID array on a separate ATA or SATA bus, or through the PCI bus with a SATA or SCSI host adapter, these problems are eliminated. Photoshop no longer has to do all it’s business from a single hard drive. It can now execute application code and read and write to disk at the same time. This translates into a significant performance boost, which can be substantial when large files are involved and a striped RAID array is used as a dedicated scratch disk. After adding RAM, and a fast startup drive, the next important hardware improvement a user can make is to give Photoshop an independent and fast scratch disk. All operations are improved- including opening files from disk and saving changes. This has a positive cumulative impact over time, as many seasoned pros adhere rigorously to the maxim "save early and often".
   
   
10. For advanced users who have implemented a separate two or four-drive striped RAID array for Photoshop’s scratch disk, an additional speed boost is obtained by saving the image file to disk at the same volume location used for the scratch disk. This is commonly known as the "work disk/scratch disk" method. In this arrangement, the scratch file and the open image file exist side by side at the same location. With the faster striped RAIDs, this provides a big boost and the fastest possible file open and save times. However, we cannot over-emphasize the importance of an established and regular backup procedure when using this technique. Data on a striped RAID volume is many times more vulnerable to permanent loss from user error, software failure, or mechanical malfunction. Use at your own risk!
    
    
    An example of using a fast striped-RAID array volume as both a ’work disk’ for the open Photoshop document, and as the designated ’scratch disk’ location for Photoshop’s temporary file.
    
    
11. For users who have implemented a separate volume or a two or four-drive striped RAID array volume for Photoshop’s scratch disk, additional speed improvements can be obtained by adjusting the disk driver settings for that volume. Third-party driver software- like SoftRAID, usually offer settings optimized for specific applications or workflows, including Photoshop.
    
    
12. For the fastest dedicated scratch disk volume performance, regularly erase it and optimize it with a qualified utility, such as Alsoft’s Diskwarrior. If you run the scratch disk at the default location on the startup disk, regular optimizations with Diskwarrior will keep directory fragmentation to a minimum, and improve general performance.