On windows xp some people recommend moving the swap file to a faster drive for better performance Would this affect Photoshop's performance? TIA

tons of discussion on a recent thread whether or not a Raid 0 scratch disk would improve PS performance. My thoughts:

First, it obviously depends on how often and how deeply your hitting the scratch disk. On the bottom of the image window you can click on an arrow and choose to display "efficiency" this is a measure, in % of how much of the function is using RAM vs the scratch disk (probably didn't word that correctly - but the lower the % the more you are using the SD. 100% means entirely in RAM)

I believe that the biggest improvement you can make is to add ram up to the point where PS can make effective use of it. In a windows system today this is about 2 gig with PS set to use about 1.7 gig. Next is to ensure the SD is on a separate physical drive that PS or your operating system. CS2 (don't know how far back) can make use of dual processors and some functions (mostly filters) can speed up using dual core, but there won't be an across the board increas in speed using dual core.

The faster the drive, the quicker you'll complete any operation that's using the SD. Whether or not raid makes a difference - that ends up being a bit esoteric for most users. If you are stiching an number of high res 16 bit images you might want to research that a bit more. IMHO you will get an improvement, but have no idea of the magnitude.

There are really two issues here; separate drive for scratch and the speed of that separate drive.

It definitely helps to have CS's scratch on a separate physical drive from the program itself. But more precisely, what you are trying to accomplish is getting CS's scratch on a separate physical disk from the OS's pagefile. The reason for this is that the OS pagefile (essentially the same thing as a scratch disk for the OS) is also tagging the main drive for overflow memory requirements while running CS (and any background programs). When the two programs are on the same physical drive, they have to share time on the I/O path to the drive they're on and this creates a bottleneck. Moving CS scratch to a separate disk eliminates the need to share and greatly increases performance.

As for speed of the scratch drive, this definitely helps too, though is a less significant factor than having the separate drive itself. To wit, I had my scratch running initially on a 250G 7200RPM SATA drive (SATA's are faster than IDE's), then moved it to a 36G 15KRPM SCSI (about the fastest you can get). The result was a 10% increase in performance on my standardized speed test running a complex, memory-intensive CS action.

However, that 36G SCSI drive cost 50% more than the 250G SATA drive, so the price/performance gain for that swap is debatable.

Now factor in RAID 0's doubling of the drive costs with its 50% reduction in reliability. You will see a marginal increase in performance at best and I think it quickly becomes clear it is a realtively poor idea. Any money spent here will most certainly be better spent on more memory and faster main drives. Actually, you would probably even be better off dedicating the second drive you would need for the RAID 0 to the OS pagefile instead...

Having more RAM than this helps, too, since that will be available to other applications.

A web browser can easily use 200-300 MB of RAM, and various stuff in XP uses around a 100 MB or more without any effort.

I'd recommend having at least one half gigabyte more than the maximum you'll dedicate to Photoshop, to reduce the chance of other applications interfering.

If only Windows XP supported some kind of memory affinity, that would be really nice.

Speaking about scratch, I stitched 24 d2x images with PTgui yesterday (4 rows of 6 images), the resulting cropped image is 17.000 by 11.000 and the tiff file is 2.4 GB...

During cropping, the PS scratch went up to 11 GB...

Cheers,
Bernard

And it's finished already?

Sorry, I didn't input my question properly What I meant was windows paging file and not the scratch file My computer > properties > advanced > performance > settings > advanced > virtual memory > change If the disk is faster - 7200 rpm - then it supposedly delivers a better performance How does that affect Photoshop? TIA

The answer is "it depends".

If you're allowing Photoshop to use more memory than you've got RAM, or Photoshop is paged to disk, then the performance of that harddrive matters, to a similar extent as the performance of the disk used for Photoshop scratch space matters.

Where does this leave the notebook users among us - where a 2nd disk is not an option, unfortunately (unless if using an external USB / Firewire drive).

I guess, that a 2nd drive of similar speed wouldn't add much value in any system (desktop or notbook), if one may assume, that normally _either_ the scratch file _or_ the Windows page file are accessed, but never both of them simultaneously? I.e. a 2-disk-setup only makes sense at all having the 2nd disk's speed far beyond USB/Firewire levels, if I got it right?

If so, then the primary option left to tackle performance issues on single-disk-systems such as notebooks is probably down to the amount of memory - what's a reasonable amount on notebooks? what are the notebook users amoung yourself experiencing / suggesting?

Thanks
Henning

It just finished 5 minutes ago... That 8 GB quad G5 is becoming more attractive every day... I am not sure whether I can wait for Vista to show up...

Cheers,
Bernard

As a notebook user, you've already sacrificed performance on the altar of convenience.


That's an assumption which I don't think you can rely on. It's not unlikely that both are accessed simultaneously, especially considering the stupid way Windows uses its page file.

What's "normal" depends on your usage patterns. If you don't run any other applications than Photoshop, it's possible that Windows won't be using its page file much. But how likely is it that you're not using other applications?


Not necessarily. The important thing is to have the second disk on a separate channel. USB is unfortunately rather unsuitable for this, but Firewire could probably work. The downside to this is that you're creating a shackle by adding that external drive.

Some laptops come with the option of two harddisks, and if those are on separate ATA channels, you can reap some benefits, but that doesn't help you if you want a notebook.

But these benefits are rather small.


A reasonable amount would be 4 GB, but I don't recall seeing that possibility in a notebook. There might be a laptop or a portable with that kind of capacity, but notebooks are in general just too small to fit that amount of RAM right now.

I sincerely regret going with only 1 GB when I bought my laptop in Singapore, I should've upgraded to the maximum of 2 GB immediately.

On the other hand, if you only use Photoshop on that notebook or laptop as a temporary solution until you get back to your big and fast computer, 1 GB should be enough for a lot of uses. Indeed, it is enough for most of my uses too, I just wish I had more.

Hehe, that was quite a long while ...


Keep in mind that in current versions of MacOS X, GUI apps can't address more than 4 GB of RAM anyway.

But the remaining 4 GB of RAM can be used as a nice ramdisk.

I'd buy that RAM from another vendor than Apple, though, Apple is charging way too much money.

Right but if the application is developed by a clever team they can split the GUI front-end from the working code (different app)...We did just that with medical imaging software earlier this year.

The only good thing about buying RAM from Apple is that it is covered by the AppleCare extended warranty... Frankly, I'm not sure if it's worth the hefty price tag (well, IMO, i'ts not).

Yes, but we're discussing Photoshop here, not some recently developed app.

Photoshop CS2's limit is 3.5 GB, BTW. I think that program could do well with a recode of several core elements as well as parts of the user interface.


Yes, that's a point.

But I also don't think the extended warranty is worth the price.

(Then again, I live in a country with pretty good consumer rights. If I were a company, my rights would be less, but I'd still be pretty well off.)

Right, I forgot that it was about Photoshop only - Sorry.

From Adobe support website it looks like Photoshop can really take advantage of more than 4GB of RAM:

..If you have more than 4 GB (to 6 GB (Windows) or 8 GB (Mac OS)), the RAM above 4 GB is used by the operating system as a cache for the Photoshop scratch disk data. Data that previously was written directly to the hard disk by Photoshop, is now cached in this high RAM before being written to the hard disk by the operating system...

I've never bothered to perform tests on my Macs to see if the ones with 8GB are really that much faster than the ones with only 4GB.

No problem. It's a useful reminder that Adobe should get around to fixing this.


No, it's not Photoshop taking advantage of it, but the operating system.


It depends on your usage patterns.

This has to do with the virtual memory subsystem of MacOS X. While I don't know the specifics of how this program works, I'm pretty certain that it doesn't prioritize file system caching over applications.

So if you e.g. run a web browser for a couple of weeks, use three or four instances of Bridge, or maybe Capture One (or goodness forbid, Aperture), these applications will be competing for the remainder of the RAM.

I won't call Adobe's advice bad, but it's certainly not the most helpful, since it seems to imply that Photoshop is getting preferential treatment to that extra available RAM. As far as I know, this is simply not the case.

If you want to guarantee that RAM is dedicated to improving Photoshop scratch disk performance, create a ramdisk.

Here's how to create a 4 GB ramdisk on the command line (you probably need to do it differently to ensure that it happens at every boot, though); lines beginning with the $ sign is the command, and the following line(s) is(are) the output from the command:



The number after ram:// is the number of 512 byte sectors, so if you multiply it by 512, you get the number of bytes in total for the ramdisk. A 2 GB ramdisk would be ram://4194304.

(Thanks to Phil Armstrong for providing this particular answer; I'm not really familiar with MacOS X yet, though I know how to go about it with Linux.)

You can then use /Volumes/untitled for your scratch disk space.

I guess this is beyond the normal Photoshop user reach?
I've been using this (or similar) technique for customers. Creating the disk at startup is no probleml...