Mac mini + Promise Pegasus for Photoshop etc...

Discussion in 'Mac mini' started by elliotn, Nov 15, 2011.

  1. elliotn macrumors regular

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    Sep 5, 2011
    #1
    Hi

    I'm thinking of getting the following to use solely as a photo workstation (Photoshop, PhotoMechanic, Raw Developer, PTGui etc.):

    - base Mac mini
    - 8GB Crucial ram
    - Promise Pegasus R6 6TB
    - 128GB SSD (to replace one of the 1TB drives in the Pegasus)

    I would put the system and apps on the SSD. All my data would be on the 5x1TB drives. I would bypass the mini's internal hard drive (maybe use it as a Time Machine backup, or a SuperDuper clone.)

    Does this make any sense?

    If it does, which SSD should I buy?

    And what RAID configuration is best for the 5 x 1TB drives - I want fast save times, but I'd also like some protection if one drive fails?

    Thanks

    Elliot

    [Ouch... I've just noticed that Apple have massively hiked the prices of the Promise Pegasus units. The R6 12TB is up 35% (now £1899 - was £1399 a couple of days ago)]
     
  2. theSeb macrumors 604

    theSeb

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    #2
    Flooding in Thailand is having an effect on HDD prices.

    I would use RAID 5, but remember tha raid is not a backup. You still need to back up your data to somewhere.
     
  3. elliotn thread starter macrumors regular

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    #3
    Thanks. I don't know much about RAID. I just googled RAID 5 and found an explanation stating that RAID 5 offers 4x READ speed, but no increase in WRITE speed. That's a problem, as I really want fast save times for large layered files in Photoshop. Is RAID 0 the only way to get fast save times?
     
  4. theSeb macrumors 604

    theSeb

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    #4
    RAID 0 will provide the best performance, but if any of the HDDs fail, then your whole array (and data) is gone. Another option is RAID 10. In general terms when comparing RAID 5 and RAID 10, the former gives better read performance and the latter gives better write performance.

    The only issue is that 4 x 1 TB drives in RAID 10 will only give you ~2 TB of useable space. RAID 5 will give you ~3 TB of space.

    The Pegasus sequential write performance in RAID 5 is not a slouch though.

    Source: Anandtech

    [​IMG]

    http://www.anandtech.com/show/4489/promise-pegasus-r6-mac-thunderbolt-review/6


    I don't think you'll have any issues with RAID 5
     
  5. elliotn thread starter macrumors regular

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    #5
    Thanks for the detailed explanation.

    Those figures look spectacularly fast.

    My references are my old G5 (late 2005) which I use as a photo workstation, and my new Macbook Air (Toshiba SSD).

    The Air saves a large Photoshop file 3x faster than the G5.

    Looking at those figures, it seems that the Promise Pegasus will save the same file 3x faster than the Air.

    That would be fantastic! I sometimes work with very large files (multi layered 16bit PSDs, from 4"x5" film scans, or stitched from multiple digital frames). These files can take 3 minutes to save on my G5. 1 minute on the Air. And maybe just 20 seconds with the Pegasus (?)

    One thing I don't understand in those Anandtech figures - '4kb random write' - what does that mean, and how does it manifest itself? That seems to be the area where RAID 0 significantly outperforms RAID 5.
     
  6. theSeb, Nov 15, 2011
    Last edited: Nov 15, 2011

    theSeb macrumors 604

    theSeb

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    #6
    Very simply:

    A sequential write is a write without intermediate seeks. This what you'll be doing when writing your large files to your disc. When you copy a file you're doing a sequential write.

    A random write is normally an operation where your computer writes to a file and needs to seek to another location and then continue writing. In a mechanical HDD this is expensive because the head has to seek to this new location.

    Effectively your hard drive is made up of sectors that can contain a part of a file. Imagine the simplest scenario where you have a hard drive with 6 sectors and each one can store N amount of data. Therefore I can store 6 * N data. The drive is empty and I try to write a 2N file. The drive will look like this (F - full sector, E - empty sector)

    F F E E E E
    (this was a sequential write)

    Now we write another 3N file. The operating system will check for available space and start writing. The drive will now look like this

    F F F F F E
    (this was also a sequential write because we found a sequential block of empty sectors to fit our file).

    But what happens if we delete the first file? The drive will now look like this

    E E F F F E

    And what if we need to write another 3N file? Well there are two empty sectors at the beginning and one at the end. This means that the first 2 sectors will be written sequentially, then the drive needs to seek to the end and write the last sector. This is a random write. This is clearly bad for performance and why you should run a defragmenting tool regularly in Windows.

    Luckily, in Mac OSX almost all of the writes are sequential, if possible, and OSX also makes sure that your drive does not end up fragmented, but, frankly, I haven't read much about how it does this.

    Edit: Here is an explanation what the apple file system does to prevent fragmentation

     
  7. elliotn thread starter macrumors regular

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    Sep 5, 2011
    #7
    Thanks again for the explanation - I think I'll be getting a Pegasus.

    I wonder if this it for price rises, or whether this is only the beginning?
     
  8. thekev macrumors 604

    thekev

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    #8
    Bypassing the internal drive is a terrible idea. If you really want an SSD, put it inside.

    Most people don't understand raid or how photoshop saves files. If you're saving big layered files, are you at 8 or 16 bpc? I think it was CS4 where they started to offer the option to turn off layer compression when saving. Basically on the G5, you weren't limited by hard drive speed. You were limited more by processors and scratch disks. When photoshop saves a large file, it goes through a lot of calculations. If the only thing involved was writing 1GB of data to disk, even on old drives you would have been finished in 20 seconds.

    You need to do some research on photoshop plugins.

    http://macperformanceguide.com/PhotoshopCS5-performance-DisallowFlateCompressedPSD.html

    http://kb2.adobe.com/cps/902/cpsid_90248.html

    How big are your files anyway? If you're in CS5 with truly massive files that go into GB, you will want more than 8GB of ram, and if you are sticking with 8GB, you'd want a dedicated scratch disk. My choice would be a small SSD in the second drive slot on your mini, assuming you're buying the mini server.

    Discreet vs integrated graphics don't mean much to photoshop unless they start to require OpenCL.


    I never found it to prevent this stuff completely. Also the directory system in OSX gets messed up easily. I couldn't live without disk warrior.

    ----------

    Beware they're noisy as hell. Also you'll want to ensure you have a functional way of hooking up pegasus + whatever display. If you're a big photoshop user avoid the thunderbolt display or anything that uses an LED backlight assuming you ever want neutral grey to actually appear grey.
     
  9. theSeb macrumors 604

    theSeb

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    #9
    Actually in the apple article it says that the sys dir is a mess, but there is reason in the madness and defrag tools can cause worse performance.
     
  10. thekev macrumors 604

    thekev

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    #10
    What article do you mean? I never said anything about defrag tools. Disk Warrior just messes with directories. It simply reduced spinning wheels and slow mapping of directories in the finder. It has nothing to do with sequential read/write speeds.

    Also I don't understand why you own an Air. The mini uses similar parts to a macbook pro. In the same situation, I'd opt for a quad core macbook pro with an SSD. It may run hot but I haven't seen the mini run much cooler. That would be faster than either of the machines you just mentioned (air and base mini). I just don't see the point in owning multiple computers with neither of them being all that powerful.
     
  11. theSeb macrumors 604

    theSeb

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    #11
    I assumed we were still talking about fragmentation and I only read up about DiskWarrior after I had posted.

    You were talking about something and I was thinking of something else.

    What does this have to do with this discussion and why does it bother you what computers I have without knowing what I use them for? I have a MBA, a MBP and a Mini and I am waiting for the new Mac Pro. I also have a crap Windows laptop and quite a powerful PC. Is this acceptable for you?
     
  12. elliotn thread starter macrumors regular

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    Sep 5, 2011
    #12
    Why is it a terrible idea? I thought that was the whole point of Thunderbolt.

    If Apple puts an SSD inside, it more than doubles the cost of the machine (base mini at £529 vs mid mini with SSD at £1,179).

    I don't fancy doing it myself on a new machine - it sounds fiddly, I'll break something.

    So I was thinking I'd put my money into the Promise Pegasus + SSD, and just use the mini as a processor, flipping it on eBay every 12 months to get a new one with a faster processor. (No DIY to put off a potential buyer.)
     
  13. elliotn thread starter macrumors regular

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    Sep 5, 2011
    #13
    Mostly, my files aren't huge. Nikon D700 and D3X files, with several pixel layers, and then maybe 20 masked adjustment layers - between 200 and 800 MB.

    Now and again I work with stitched files from PTGui. These can be quite big - between 1 and 2GB.

    I was thinking of creating a scratch partition on the Pegasus RAID 5 array.

    ----------

    Hmm, 'noisy as hell' sounds bad! I like a low level background hum (masks the tinnitus!), but I don't want a hair dryer under my desk. Anyone confirm that these things make a racket?

    Re. display, I was planning on plugging my Eizo CG275w into the Pegasus with a miniDP to DP cable.
     
  14. philipma1957 macrumors 603

    philipma1957

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    Howell, New Jersey
    #14
    yes you got it and you can buy low cost small ssd's as raid0 a pair of 64gb ssd's in a raid0 are fast.

    I have a promise I have 2 samsung 64's as a raid0

    I have an intel 600gb ssd as boot drive

    I have 3 1tb hdds as back ups. run as jbod. they do a clone of the intel every other day.

    I have the two internal 750gb hdds on my server as

    time machine a and time machine clone.



    the intel is a fast boot /osx / iTunes / drive

    the 1 tb hdds make good superduper clones of the intel

    the 2 ssds are fast as scratch drives.


    and in a year or two I will replace the server.


    I still have 3 1tb hdds I have not used.

    this was not that expensive until prices hit the roof on hdds.
     
  15. thekev, Nov 15, 2011
    Last edited: Nov 15, 2011

    thekev macrumors 604

    thekev

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    #15
    The point of thunderbolt is external PCI support/ high bandwidth connections. I can't recall if it supports system boot, but you'd be placing your boot drive on a shared channel with your data. You'd be better served with that drive inside it. Apple doesn't have to do this for you. You could use the same ssd you were going to put in the promise enclosure in the mini. It uses 2.5" drives.

    Perhaps I typed in the wrong place. I meant for the OP. He owns an air + an old G5. He was going to buy a base mini on top of it. It would be faster, but i'm not sure the increase in speed on the computer end will be up to his expectations. I wasn't referring to you (sorry if I made it seem that way), and yeah I'm waiting on the new mac pro too :).

    "Scratch partition" is a bad idea no matter how you look at it. You know I have been through so many computer headaches myself that I don't really want to see others go through similar ones. If you were partitioning a backup boot drive or something like that and using the fastest portion for scratch allowing a generous amount of extra space, that might work. The problem with your method is it will be accessing the same disks when it reads data and has to scratch portions of this data. It's going to put a lot of unnecessary wear on your drives, and partitioning a prosumer grade raid box into two raids over a single controller is just asking for problems.

    It's kind of like I said before. It sounds like you are just going to end up spending a lot for what you gain in performance. Depending on where your data is currently saved, the raid might be beneficial, but my thoughts are that you'd probably see the biggest gain via a lot of ram due to 16 bpc files at the sizes mentioned. 16 GB for a mini is still cost prohibitive today, but that may change soon enough. You can partially determine your benefit from ram in CS5 on (which is 64 bit mac side) via keeping an eye on scratch sizes and disk paging (via activity monitor). If you're working with large files, I can give you a checklist to help conserve ram and speed up your system. It was designed more around the old 32 bit limitation though.

    Regarding noise factor, take a look at the Apple site. Go to the promise enclosure and look at comments. You'll notice the two biggest complaints are DOA drives and noise factor. Most of these external enclosures are pretty audible. If you find a good one that uses high quality fans, it can be much less of an issue. I've upgraded fans on some personally. I haven't looked at what is inside one of the Promise enclosures. Cheap fans do get noisier as they age.

    Regarding the Eizo it's an excellent display. Edit: oops got threads mixed up, it was someone else that was marked as from the UK, thus the reason for being jealous of their pricing from Eizo. The CG275w has a mini displayport connection, so you wouldn't need to use an adapter. I would ask Eizo first if this configuration works properly. They're very good about testing (I switched to them after three bad NEC experiences even though some of the NEC people are really nice).

    Bleh that got really long.
     
  16. theSeb macrumors 604

    theSeb

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    #16
    Heh. I couldn't figure out how you knew what I owned so, in retrospect, I should have guessed you weren't replying to me. That's what I get for posting at 1 am.
     
  17. elliotn thread starter macrumors regular

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    #17
    Many thanks for the detailed reply. I'd probably buy a new Mac Pro if it were available - fill it up with 3TB drives and be done with it.

    True, the base mini won't be massively faster than my Air (8Mb vs 4Mb ram will be noticeable, and there's a slight increase in clock speed). But I already find my Air speedy - it runs my Photoshop actions 3x faster than my G5 (I take the point that 3x faster save times could be as much to do with Photoshop architecture as disc speeds - I'm running CS2 on my G5, and CS5 on my Air).

    One point of getting the mini is simply to have a separate computer for photography (the Air gets used for everything else, and the G5 goes to landfill). But maybe I should go for a more capable version for the times when I work with really big files. Maybe the mini server - put in two 128GB SSDs, one for system and apps, the other as dedicated scratch disc, and use the Promise Pegasus at it's default configuration (RAID 5?) for all data (working files and archive).

    Re. the Eizo CG275w - yes, I'm in the UK, so I got it relatively cheap.
     
  18. elliotn thread starter macrumors regular

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    #18
    I managed to find a dealer selling Promise Pegasus units at pre-flood prices - http://www.jigsaw24.com/

    I've bought the R6 12TB for £1379 (incl VAT). £520 less than Apple. It will arrive next week.

    I still haven't decided which Mac mini to pair with it. Initially I'll take it for a spin with my Macbook Air.

    Elliot
     
  19. elliotn thread starter macrumors regular

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    #19
    The Promise Pegasus has arrived and fortunately it's not 'noisy as hell'. It's not silent, but I don't think I'll notice it under my desk.

    Re-reading this thread, I think thekev's advice - to leave the Promise Pegasus as is (RAID5), and to get a more powerful mini, with system/apps on one internal SSD, and scratch on a second internal SSD - is probably most appropriate for me. (I appreciate that Philipma has experimented with more exotic configurations of his Promise Pegasus, but I'm not a natural tinkerer.)

    I'm still wary of cracking open a brand new Mac mini to install SSD drives, so I'm now looking at the mini server with two Apple-installed 256GB SSDs.

    It's arguable that I only need a 128GB SSD for system/apps, and a 64GB SSD for scratch. If I did install these myself, I would saving myself over £500 compared to Apple's 256GB/256GB option (I'm looking at the prices for Crucial M4 SSDs).

    - What brand SSDs does Apple install in it's Mac minis? Presumably Apple has tested them and is prepared to stand by them (?)

    - If I install SSDs myself (e.g. Crucial M4 or Samsung 830), can I be confident that they will work (and continue to work) in a mini?

    - Is there an online video guide to swapping drives in the mini Server?

    Thanks

    Elliot
     

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