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Which Computer configuration for digital Imaging

John,

When a computer program needs more memory capacity than the installed RAM provides, it will use a technique called "page swapping" whereby a chunk of the data in RAM is written to hard disk so that the RAM is freed up for the next thing the program wants to do. This is covered under the heading of "virtual memory" in Windows. Later, when the data which was temporarily written to disk is needed again by the program, another chunk of data is written to disk so that the earlier data on the disk can be read back into the RAM again. These chunks of data are sometimes called "pages" and therefore the technique is called "page swapping". The Windows operating system calls it Virtual Memory, and Photoshop opens a temporary file for the purpose on whatever hard disk you defined under Edit>Preferences>Plugins & Scratch disks.

Once Photoshop gets into page swapping, the performance will suddenly slow down dramatically, especially if you've left the scratch disk setting at the default "startup" setting. Photoshop will usually give a warning about degraded performance if the scratch disk and Windows Virtual Memory disk are on the same disk partition, and recommends using a separate physical drive for the scratch disk.

You mentioned in your earlier post about adding an extra 512MB of RAM, that Photoshop no longer "seized up". That seizing up was due to the slowness of swapping the data between memory and the scratch disk. Even with the extra 512MB, Photoshop will still seize up on you if you perform enough operations on the image to run out of RAM and get into page swapping. To see what I mean, try rotating an image 90 degrees many times in succession, until the allocated RAM gets used up.

If the amount of RAM you now have is enough to do the usual image adjustment operations without getting into scratch disk usage, then you needn't worry about any of this. But if you are frequently running out of RAM, then a high performance scratch disk may be cheaper than buying extra memory.

The highest performance scratch disk is usually a RAID Zero (or RAID0) pair of IDE hard disks. "RAID" means Redundant Array of Inexpensive Disks. RAID Zero is a non-redundant mode whereby the data is striped across the array of disk drives, thus increasing the read and write performance dramatically. This is the best thing to use for a scratch disk because Photoshop can get the data on and off the RAID Zero array much faster than it could with just your c: drive.

You can buy a PCI RAID host adaptor and then you connect two new hard disks to that. Then in Photoshop you define the RAID0 array, which will have a drive letter like e: under Edit>Preferences>Plugins & Scratch disks.

You can also define a RAID One (RAID1) array whereby two drives are mirrored. The data is written to both drives simultaneously, thus protecting you from potential total data loss in the event of a disk drive failure. RAID1 doesn't provide any performance benefit, so for the purposes of the discussion in this thread, RAID0 should be of the main interest.

The RAID0 array must be defined in Windows 2000 under Control Panel>Administrative Tools>Computer Management>Storage. Here one would set up a 4GB partition at the start of the RAID for the scratch disk, and the remaining part of the RAID can be used for your image library.

I hope this answers your question.

Kind Regards,

Craig
 
Posted by Richard C&bell (Rc&bell2) on Sunday, November 30, 2003 - 2:48 am:

For all you people having difficulty with Photoshop and memory here are a few tips. One, check your scratch disk settings and make sure that you are using different disk for start and running program, if your drive is partitioned this setting can be critical= i.e. the first two settings should be for different places on your drive. For best performance, scratch disks should be on a different drive than any large files you are editing. * Scratch disks should be on a different drive than the one used for virtual memory. * Scratch disks should be on a local drive. That is, they should not be accessed over a network. * Scratch disks should be conventional (non-removable) media. * Raid disks/disk arrays are good choices for dedicated scratch disk volumes. * Drives with scratch disks should be defragmented regularly.

Just a quick note. I think this post is intended to say that you need to use a different PHYSICAL drive, not a different partition on the same drive. If you simply use a different partition on a single drive, you will make things worse because the head will have to travel back and forth much more than the head on a separate drive which can operate in a more or less fixed position when it works.

2) If you routinely clear the history of the image it will reduce the file size. 3) Remember to check your cache settings too- you can safely use half the RAM on your computer and still run Photoshop by itself. 4 Close everything else when doing serious photo editing 5)Edit as much as you can in RGB PSD, the most efficient place for Photoshop to work. 6) When saving monster size images, uncheck image preview in preferences, it will decrease the size of the file significantly. 8) Stop storing all your images on the hard drive if they consume a significant amount of space and go to CD's and back ups to reduce the amount of disk spaced used by image storage. If you re- save and close and re open the file, it should be sufficient to maximize efficiency- you do not have to completely close and open the program to "release the ram". If you are using a mac G4 with 256 RAM, that should be more than enough for large file sizes- 5-8 MB images to 10-20MB images.
 
Dear Craig,
Thank you very much indeed for taking so much trouble to provide such a detailed and clear explanation. The concept is certainly much clearer now. I shall definitely bear your comments in mind and take your advice if I start to get into difficulties with Photoshop again. This could well happen soon as I seem to be acquiring ever larger files.
Thanks again,
John

Thanks also to Richard and Don
 
Dear Craig,
Sorry to bother you again but I have just reread your post and there is one more point - when you refer to connecting two new hard disks to a PCI RAID host adaptor, I wonder if these are internal or external disks? It's just that I aready have two hard drives and I don't think there is room for more inside the machine.
Sorry for my denseness.
Thanks
John
 
Hi John.

A PCI RAID host adaptor controls internal ATA hard disks only.

Best,

Craig
 
Correct on the notes added to my first mention of techniques to save RAM in Photoshop. I did mean that a different drive altogether for start-up and running the program in scratch files settings is important. If you have a partition it will not make the computer run Photoshop faster. I have found it is preferable not to have a partitioned drive, but if one does, it is especially important to have a separate drive to go to. I find that having two different drives seems to separate the wheat from the chaff too. Richard
 
It is hard to tell from the initial post as to what degree the guestion needs addressing... is it conforming an ideal computer system for digital imaging workflow... or is it to expand on an existing one? Also, the degree of photographic needs is a key piece of missing information. Workflow speed and reliability is a far more critical issue for me as a wedding photographer and commercial shooter, than it is for a casual shooter.

Assuming it is a search for an ideal photo imaging system, I would also opt for a Mac system. It is the standard in the graphics, advertising and photographic industries. As such, the features and work flow design tend to be skewed toward these functions.

I know many photographers who started out with PC and eventually switched to Mac. Some others have remained on PC, but only because their investment is already to great to switch... but they have come to regret that PC investment as Mac continues the refinements aimed at the industries listed above... most of which photographers can benefit from.

I also agree that the latest greatest isn't necessary to maximize a computer system. A dual processor Mac G4
can be had now for a lot less than just a few months ago (due to the launch of the G5). And Lynns earlier suggestions are quite sound concerning other Mac solutions.

Were I conforming a new system, I'd limp along with what I had for as long as possible... until the G5s start becoming more reasonable (which already has stared to happen). The advantage is that the G5 Dual processor machines are expandable to 8 gigs of RAM.
This is of course overkill. But perhaps not in the future. For ex&le consider the advancements in Photoshop CS where many, many more functions now work in 16 bit, which means much larger file sizes. Plus the meg count in cameras is accellerating at a fierce rate.

My G5 has 4 gigs of RAM right now (expandable to 8). With the 2 processors and that amount of RAM, I can print on 2 printers (Epson 2200 and a Kodak 8500), be working in PhotoShop CS with an entire 2 gig CF card open in the browser, and be burning a DVD all at the same time with no effect on the speed of functions in PhotoShop with a 94 meg, 16 bit image open for correction.
 
>I agree with all of the statements Mark Williams makes about the Mac and PC. As a computer instructor who laughs continually at the nightmare that is Microsoft, I have two things to say. If you want your operating system to get in the way, freeze up, and offer you an irritating array of extra choices to compensate for the fact that the initial programming and design is flawed, you will get the one bonus of PC's- they are cheap. However, if you are serious about graphics and photography, the smooth integration of systems, and do not mind paying the price tag for thoughtful design, then Apple Computers are the superior system by miles. Simply put, one system is fun to work with, the other is just work. I will not even go into the subject of computer viruses! RC
 
> I second that, Richard is right. My studio has used both Mac & PC > computers for the past five years or so and I have begun to loath the > now lone PC (the others have died). I have endless problems with the > pc and I do not trust it with any vital data. The macs on the other > hand just work and are a pleasure to use. Mercedes vs. donkey and > cart. The price is the most attractive reason to buy a pc and with > the deal that I got from Dell last time I could not refuse, but when > you add up the cost of repairs, tech support, useless virus software, > lost data from crashes and lost time the mac would have cost a lot > less.
 
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