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MBP with 16 GB of RAM : is a scratch disk still mandatory ?

Feb 12, 2013 8:15 AM

Hi,

I will have to replace my two computers in a row: a trusty Intel iMac 24 white, mate screen, still good but painfully slow when it has to apply complex filters on 21 Mpx files, and a PowerBook G4 17". The latter is incompatible with Intel software (already dropped by Lightroom 3), and the 2006 iMac support has been dropped with the launch of Lion. So! I'll have to bite the bullet and buy a new workhorse first, forgetting the portable solution for quite some time for budget reasons… I first considered a new iMac 27", but some specs made me look at the Mac Mini with Fusion drive instead, as the tiny machine has awesome performances and takes some great third parties monitors (NEC etc), and for the iMac's price. The only feature I might miss from the iMac is the Retina display.

 

But then I thought that maybe, I could kill two birds with one stone! Or kill one bird and have at least half of the other, if using a MacBook Pro in clam-shell mode as my daily workhorse could be imaginable (I'd have to add the price of a good monitor). I had first put that idea aside when I saw that the MBPs are limited to 8 GB of RAM on Apple's website. But then I found a retailer who packs them with 16 GB of RAM, and even with an additional SSD drive in place of the SuperDrive, allowing FusionDrive to be set. Equipped that way, the MBP should be a rocket compared to my current iMac Jeep! Not that I need that much power now, but considering that I replace my computers every 5 or 6 years only, I'd better make sure that it is suitable for the trip.

 

Now, reason has it's reasons not to spend overly for unnecessary features. I probably wouldn't benefit that much from a SSD as the main drive, since booting and launching apps is not what consumes time. Also, the files to work on are on external USB3 drives (I'm glad I took that option a couple of years back, even if I have not been able to use them at speed so far). What really takes time in that work, besides computing itself, is the Photoshop scratch task. So I thought that maybe, FusionDrive isn't something I really need either since it won't be possible to assign the SSD itself as a scratch disk, and I'm neither sure that ML will set large blocks aside there and allocate them to Photoshop. Maybe it does. But because of the way Photoshop works, I could probably purchase a small external Thunderbolt SSD, and set it as Photoshop scratch, and occasionally for Final Cut, and spare. And thus, keeping the SuperDrive in, which will certainly be handy in few occasions.

 

But, maybe I won't even need a scratch partition! I have looked at the scratch file sizes for my work, and the average size is 2 to 3 GB. No wonder my iMac is so slow with it's max of 3 GB of RAM ! The fastest scratch disk I can set now is an external FW800 Lacie, quite slow by today's standards and so noisy that I have long let go of that setting. But with 16 GB of internal RAM, a 7200 rpm 750 GB disk and external USB3 storage, I expect the MBP to be set to make wonders, without any costly or geek aware addition.

 

The thing I'm not sure about yet is how Photoshop balances RAM usage and scratch writing. If there is enough RAM (would in my case 16 GB for say: two open documents with 2 GB of work files each, suffice?), will the scratch partition become unnecessary? I think it should work fine with the single partition, but please correct me if I'm wrong!

 

Lastly, if there is any experience in using the MBP in clam-shell mode extensively that you wish to share, good or bad, I'd gladly take it. I am a little concerned with heat and lifespan. Ouch, what a lengthy post… Thanks for having read it through!

 

… Oh! Yes… what do you think of the Hi-Res Antiglare Widescreen Display option? I would take it but I have not seen one in any of the shops I visited.

 
Replies
  • Currently Being Moderated
    Feb 12, 2013 8:40 AM   in reply to alpshiker

    Yes, you need a scratch disk.  If you do large files with lots of layers you could use 100-200 gigs.  There was a recent post on scratch files and Mac and it seems they are hidden so you may not be seeing what you think you are seeing.  3 gigs seems really light for a scratch file unless a really simple edit.

     

    You say it will not be possible to assign the SSD as a scratch disk, why not?

     

    With a USB3 connection, or SATA3 connnection you could use an external as scratch.

     
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  • Currently Being Moderated
    Feb 12, 2013 8:49 AM   in reply to Curt Y

    The scratch file will be initialized to the same size as the RAM available to Photoshop. The scratch will grow only if required. An initial 3 GB scratch sounds correct for alpshiker's machine which provides no more than 3 GB RAM to Photoshop. Depending on type of work being done in Photoshop, document size and History size, it's possible for the scratch to never grow beyond its initial 3 GB size.

     
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  • Currently Being Moderated
    Feb 12, 2013 8:54 AM   in reply to alpshiker
     
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  • Noel Carboni
    23,471 posts
    Dec 23, 2006
    Currently Being Moderated
    Feb 12, 2013 9:24 AM   in reply to alpshiker

    Just some idle thoughts...

     

    In my opinion, in this day and age no one should buy a new computer that boots and runs from spinning hard drive storage.  SSD has arrived, and the prices keep dropping.  Anything less than SSD is simply not future-proof.  That's not to say you can't have some HDD storage too, but don't configure it to be used in real time.  I'm personally not a fan of "hybrid" solutions either, as they complicate the thing you want to be utterly reliable:  Not losing your data.

     

    Yes, I understand that SSDs are significantly more expensive than HDDs.  They're well worth the price difference.

     

    The responsiveness of a computer running entirely from SSD is nothing short of amazing.  To the point that once you've used one you'll never, ever, want to use one running from spinning storage again.  You realize that you were waiting for things all the time.

     

    Modern processors are capable of chunking through data so very rapidly that HDDs really hold them back.

     

    For example, you really don't need to worry about providing a second drive for Photoshop scratch if you have all SSD storage, as there's no potential for thrashing.  Thus you COULD outfit a system with a single gargantuan SSD-based system volume and nothing else.  All your free space is available in one place, and everything just works more simply.

     

    Of course, nothing stops you from having extra spinning hard drive storage for low-access data, backups, etc.

     

    -Noel (living the SSD dream since April 2012).

     
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  • Noel Carboni
    23,471 posts
    Dec 23, 2006
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    Feb 12, 2013 11:05 AM   in reply to alpshiker

    Why should the scratch files have to be in an alternate partition?  I have no experience with hybrid drives, so I don't how they would handle the writing and reading of temporary files.

     

    -Noel

     
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  • Noel Carboni
    23,471 posts
    Dec 23, 2006
    Currently Being Moderated
    Feb 12, 2013 11:30 AM   in reply to alpshiker

    A separate device is not the same as a separate partition.

     

    Adobe's intent is to have you use multiple SATA connections simultaneously, and to keep heads in a spinning drive from seeking back and forth as multiple processes try to use it simultaneously.

     

    Partitioning a drive will likely make more seeking happen (again, thinking strictly of spinning HDD here), not less.

     

    -Noel

     
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  • Currently Being Moderated
    Feb 12, 2013 11:43 AM   in reply to alpshiker

    From what I understand programs can not access "large blocks".  THey write to whatever is availble.  To me the advantage of a partition is it is a defiened space of "neat freeks" and it minimizes fragmentation on the rest of the disk.

     
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