9 Replies Latest reply on Nov 21, 2012 1:53 AM by mixapix

    Cache size and SSDs (CS4 on a Mac Pro)

    mixapix Level 1

      I'm trying to figure out how many/how big drives/SSD or hard drives I need to get for a quad-core Mac Pro, and am stuck when it comes to the scratch disk.

      I plan to upgrade its memory to 12 or 16GB (I've heard this is enough for most uses).


      1) How do I determine how big a scratch disk needs to be in Photoshop CS4 extended (Mac)?

      I've come across a few sites which explain how to calculate this but they're very technical and hard to grasp IMHO.


      2) Where do SSDs come into the equation? Obviously they're still too expensive and small for file storage, but will a SATA-3 SSD (connected to a SATA-3 PCIe card if the onboard SATA-3 interface will be a bottleneck) do wonders as a scratch disk? I've read opinions that go both ways on this. Or are they mostly for use as a system and applications boot drive? And does it make much of a (real world) difference to use a SATA-3 SSD/PCIe interface or just stick with the SATA-II interface already available?


      3) Apart from Photoshop, do other applications use a scratch disk as well (Lightroom for instance, which I also use)?

      It seems a waste to dedicate a hard drive or SSD just for Photoshop alone.



        • 1. Re: Cache size and SSDs (CS4 on a Mac Pro)
          Curt Y Level 7

          Scratch disk size depends upon what you will be doing.  If just minor stuff then 50 gigs might be enough.  More serious stuff, like large images and lots of layers may take 100 - 200 gigs.   Saw one opinion that stated your scratch disk should be 100 times larger than your largest image you will work on.


          You can get SSD in large sizes, but of course they are spendy.  They are extremely fast to read from.  Again it all depends on how much demand you will be putting on the system.

          • 2. Re: Cache size and SSDs (CS4 on a Mac Pro)
            Brett N Adobe Employee

            1) Photoshop creates a scratch disk the same size as its RAM usage, which is generally about 70% or your available system RAM. So with 12 to 16 GB of RAM, you will have about 8 to 12 GB of scratch disk allocated. Photoshop's RAM usage is determined in Preferences > Performance.


            2) SSDs are good for performance, not for storage (too expensive). So anything that might be in active use a lot, such as the scratch disk, should be on an SSD if possible. The Photoshop scrach disk should be on a separate drive from the OS and its scratch disk (called a paging file on Windows) when possible.


            3) Lightroom doesn't have a scratch disk. The Photoshop scrach disk is where an image is stored while it is being worked on. Lightroom doesn't work in the same way, it doesn't really open images. However, it references and rebuilds image previews constantly, so these should be store on an SSD when possible.

            • 3. Re: Cache size and SSDs (CS4 on a Mac Pro)
              Lundberg02 Level 3

              It's SATA III no matter what, but a SSD eliminates the seek time and is way faster for read writes, coming closer to physical RAM.

              • 4. Re: Cache size and SSDs (CS4 on a Mac Pro)
                Noel Carboni Level 8

                First, let me say that I'm a PC expert, not Mac, but the concepts can apply.


                Re-examine your suggestion that SSD is too expensive to be used for general storage.


                My suggestion:  Create a RAID 0 array out of multiple high performance SSDs connected via SATAIII (6 gbps) and use it for everything.  Don't skimp on the cost, make the array big enough so that you can put your OS and data on it and still have gobs of (e.g., 50%)  free space.  That's not to say you can't keep some spinning HDDs also in the system as well, for low-access data.


                Yes, this is expensive, but SSD prices are dropping and it's not going to break the bank.  Think about what your time is worth going forward..


                I'm living this dream.  In April I created a RAID 0 array of 4 x 480 GB SATAIII SSD drives (OCZ brand) on which I have installed Windows 7 and all the data I access on a daily basis.  At the moment I have about 1 TB of free space remaining of the nearly 2 TB total.  I can sustain data throughput to/from the drive array at 1.7 gigabytes / second, and latency is around 0.1 milliseconds.  I also have 3 TB of spinning HDD internal storage for files I only rarely need to access.


                This configuration accelerates EVERYTHING.  All disk access is instantaneous.  I literally can't tell when Photoshop accesses its scratch files.  It's like using a computer from Star Trek instead of one from 2012.


                Just a thought.  Watch for sales, big SSDs can be purchased for WELL under a dollar a gigabyte now.  If that still seems expensive, consider that HDD storage was at that price density not all that many years ago (less than 10).



                • 5. Re: Cache size and SSDs (CS4 on a Mac Pro)
                  mixapix Level 1

                  Having a Star Trek computer wouldn't be such a bad thing

                  So you've basically got just a single 480GB drive which contains Windows, Photoshop and your other programs, your files and as well as being a scratch disk? I guess with a good workflow that could work: edit the files in question and at the end of the day you transfer them over to the 3GB regular hard drive for permanent storage. I've read so much about the need for separate drives for everything, but maybe this isn't as important when you run a 4x RAID-0 setup as yours, being extremely fast in any case.

                  Alas I don't have the finances (or needs, although wants is another issue) for anything like that right now, but definitely something to keep in mind for later.


                  Since the Mac Pro has room for 4 SATA drives, an empty optical drive bay which can take up to two SSD drives (with a suitable caddy/adapter) and 4 PCIe slots my plan so far is as follows:


                  - 2x 2TB SATA-3 hard drives in RAID-0 (striped) mode for file storage

                  - 2x 3TB SATA-3 hard drives in RAID-1 (mirrored) mode for Time Machine backups

                  - 1x (perhaps 2x later, in RAID-0 mode) SSD drive(s) as the boot drive (for Mac OSX and all my applications). I've got my eyes set on a 240GB OWC Mercury Extreme Pro 6G given all the rave reviews. It seems to have some better wear-leveling technology than most other drives, or so I hear.

                  - 1x OWC Mercury Accelsior PCIe dual SSD card (RAID-0 striped I believe, for extra high speed) for scratch disk. I'm hoping the 120GB model will suffice.

                  A more cost effective solution would be to just use a standard single SSD via a SATA-3 PCIe installable controller card (the Mac Pro has SATA-2 in its drive bays). Even lower cost would be to attach a standard SSD drive connected to the empty optical drive bay's SATA-2 connector. But I suppose trying to aim for the fastest solution here (OWC Mercury Accelsior dual-SSD RAID-0 via SATA-3) would make a noticeable difference.


                  I see there are different opinions on scratch disk sizes, so I should probably avoid getting a really small drive. What happens when I occasionally work on some really huge files and the scratch disk won't do? Will Photoshop continue writing to the next drive in the list of assigned scratch disks and finally use the boot drive if there still isn't enough space available?


                  Regarding Lightroom: it doesn't write any temporary files at all? In other words; it can't take advantage of the scratch disk which Photoshop will use?

                  • 6. Re: Cache size and SSDs (CS4 on a Mac Pro)
                    Curt Y Level 7

                    If you use Bridge you can put the cache on the scratch drive.


                    An yes if you have multilple scratch disks checked in PS it will use them if not enough space on primary.

                    • 7. Re: Cache size and SSDs (CS4 on a Mac Pro)
                      Noel Carboni Level 8

                      mixapix wrote:


                      Having a Star Trek computer wouldn't be such a bad thing

                      So you've basically got just a single 480GB drive which contains Windows, Photoshop and your other programs, your files and as well as being a scratch disk?


                      No, I have a RAID 0 array of four of them, each of which has 480GB, for a total of 1.74 TB (per Explorer, which uses powers of 2) or 1960 GB (decimal).


                      Yes, the OS boots from there, swaps to/from there; Photoshop runs from there, its scratch points there, my photos that I work on are there, my output area is there.  Everything that needs hyperfast disk access gets it.



                      • 8. Re: Cache size and SSDs (CS4 on a Mac Pro)
                        Lundberg02 Level 3

                        If your Mac Pro is SATA II everything is less than SATA II, regardless of what the label says.

                        • 9. Re: Cache size and SSDs (CS4 on a Mac Pro)
                          mixapix Level 1

                          Curt Y: yes, I do actually use Bridge, so that's an excellent suggestion for other uses of the scratch disk!


                          Noel Carboni: I think I may have misunderstood RAID-0, thinking that it just made read/write access faster but not multiplying the size. In other words: 4x480GB drives in RAID-0 would still mean a single 480GB drive as far as Windows/OSX is concerned, but using 4 "lanes" for parrallel and super-fast access of the data.


                          Lundberg02: I've read that the Mac Pro has internal SATA-II connections for each of the drive bays but by utilizing a SATA-III card in one of the PCI-express (PCIe) slots you can get SATA-III speeds (with SATA-III 6G drives of course) connected to that card.

                          I was wondering if SATA-II or III would matter for the boot drive as this forum posting confused me where it said:


                          The answer to if you need/could benefit from a 6G/pci-ssd is hidden in the way you want to use the drive.

                          If you want a boot drive which makes your softwares super-snappy you can go for any kind of drive with high 4K read/writes. A 6Gbps ssd in a 3Gbps connector will work fine since the 4K read/writes are so far from the bandwidth bottleneck in the 3Gbps interface. Samsung 830 would be my choice of drive here due to its good performance and amazing reliability.


                          On the other hand, if it is bandwidth you are after there are several options depending on what you want to spend Remember that bandwidth is not super important for a boot drive, so these does not have to be bootable

                          * upgrading the standard drive bays in a mac pro to sata 6Gbps, http://blog.macsales.com/12247-upgra...ys-to-sata-3-0

                          note that this will make the drive bays "un-bootable" but you can still take one of the extra Sata ports on the motherboard and put a boot drive on that. With this you can add 4 6Gbps ssds to the standard drive bays in the mac pro and raid them.

                          * accelsior SSD from owc (these can be raided as well, look at http://macperformanceguide.com/Revie...e-stripe3.html for numbers).

                          * revodrive. Not bootable, but the Revodrive and Revodrive x2 (NOT!! Revodrive 3) are usable with mac osx. They have about the same max-performance as the accelsiors but are somewhat more limited. And usually more expensive (at least here in Sweden).


                          What exactly does he mean above (colored in red)? That I won't benefit much from a 6G drive connected to a SATA-III interface (for a boot/applications drive) and might as well use the built-in SATA-II connector?