Wanna get an OWC Pro SSD 120 GB -- how much do I need to lose?

Discussion in 'MacBook Pro' started by miata, Dec 1, 2010.

  1. miata macrumors 6502

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    #1
    Looks like my company upgrade got postponed for a few months due to budget constraints. As a short-term boost I'm looking at getting an SSD, but I'm a little worried about the capacity.

    I currently have a 320 GB drive and have been able to get by usage down to 93 GB. Will I need to worry about leaving headroom with a 120 GB SSD drive?
     
  2. ihonda macrumors 68000

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  3. Mabyboi macrumors 6502

    Mabyboi

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    #3
    I use a 160GB intel X25-M and its more than enough for my whole system + games. I store everything else on flash drives or my 1TB time capsule... I think 120 is more than enough.
     
  4. Saturdays macrumors member

    Saturdays

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    #4
    I just installed my 120 GB OCZ Vertex II like 30 min ago. Its great already notice improvements in everything. I might get the optibay but I am not 100% sure yet, gonna test out whether or not i'll need it first.
     
  5. miata thread starter macrumors 6502

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    #5
    My concern is that I was able to trim down to 93GB from around 200 GB, but I'll quickly sneak back up to at least 100-110 GB if I am not careful. I recall reading that you really want to leave lots of headroom for maintaining good performance with SSDs
     
  6. miata thread starter macrumors 6502

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    #6
    I thought about this. I really wouldn't miss the internal SuperDrive, but I already have a bunch of data tiered off on external storage. I just don't want to make things more complicated by adding yet another storage tier.
     
  7. ihonda macrumors 68000

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    #7
    then get a time machine and it will be wireless storage..?
     
  8. miata thread starter macrumors 6502

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    #8
    Not sure I follow. I already have Time Machine off my Airport Express for backup. I have tons of other storage while I am at home. The problem is that most of the time I am at work or on the go. I need to keep my data with me.

    I guess the real question is how much headroom is recommended for an SSD drive?
     
  9. spork183 macrumors 6502a

    spork183

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    #9
    That drive from OWC has 7% Over Provisioning build in beyond the 120. However, if you are talking about drive creep, you'll eat that extra 25gb in no time. Get an external fw 800 case from OWC and drop your existing drive into it. Adds less than a pound to your weight. Who says you can't take it with you? :D
     
  10. miata thread starter macrumors 6502

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    #10
    I'm a little worried about drive creep, but I should be in a new system in a few more months. I'm trying to figure out how much headroom is recommended for SSD drives like the OWC Pros.

    I already have one of those cases that I use for mirroring my system disk with CCC. They are very nice, and I appreciate the suggestion.
     
  11. alphaod macrumors Core

    alphaod

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    #11
    Just buy the OCZ Vertex 2; I don't see why you need to pay more for the OWC version of the same drive.
     
  12. Mabyboi macrumors 6502

    Mabyboi

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    #12
    Mine is at around 110 or 120 now, it seems to be fine.
     
  13. miata thread starter macrumors 6502

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    #13
    I just checked Amazon and the OCZ Vertex 2 is $250 versus $239 for the OWC Pro SD 120 GB direct from OWC. From Newegg the OCZ 2 is $249 after tax. So, OWC seems to have the best price for me -- besides I've been using them for many years with close to 100% satisfaction.
     
  14. Stvwndr219 macrumors 6502

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    #14
    My 80GB intel SSD is at 79 GB, no issues so far..
     
  15. miata thread starter macrumors 6502

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    #15
    So, you are still at less than 75% utilization.
     
  16. Voondebah macrumors member

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    #16
    I would try to leave 10-20% of the space free. Have you tried the tool GrandPerspective? It maps out all the files on your drive so you can easily pinpoint the big files.

    In preparation for your ssd, have you done any changes to the hibernate mode? Normally your system writes memory contents to disk when it sleeps just in case the battery dies, so it can recover the machine state from the hard drive. You can change the hibernate mode to not write the memory to disk, and save a few gigs of space.

    Go to terminal, and run the command:
    sudo pmset -a hibernatemode 0

    you will probably have to type in your password. Afterwards, you can remove the sleep image. Run the following command to remove the image:
    sudo rm /var/vm/sleepimage

    The disadvantage of changing the hibernate mode is that if the battery dies, you will not be able to restore the machine state, so if you had any unsaved work, you're out of luck.
     
  17. miata thread starter macrumors 6502

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    #17
    I would be pretty close to 20% if I migrated today, sounds promising.

    I've used Disk Inventory X which seems very similar to GrandPerspective. Lately, I started using OmniDiskSweeper which I like even more. Both of these helped me to get from 200 to 93GB.

    I'm pretty sure I killed hibernatemode a while back. And /var is only 4 kB.
     
  18. Voondebah macrumors member

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    #18
    Well, it sounds like you've got a good handle on things! I would say you're good to go then. You just need to avoid filling up too much of that empty space since there isn't any TRIM in OSX.

    My understanding is that blocks in an ssd cannot be overwritten - once written to, they have to be erased before they can be written to again. The issues comes that when you delete files from a system without TRIM, these blocks are not erased. The drive will attempt to use all of the free, unwritten blocks first when writing files, but eventually they will run out. At this point, the blocks that are free but haven't been erased have to be used. This is what you want to avoid, since now writes will require the block to be erased first, and then written, slowing things down. The idea of TRIM is to erase these blocks when the file is deleted (or at a convenient time when the drive is idle) to avoid having a drive full of these "free but full" blocks.

    So, if you have extra space, you can delay the point at which this would happen. Controllers have a degree of garbage collection to also help with this issue. The drives in the new macbook airs have very aggressive garbage collection to make up for OSX lack of TRIM - if you haven't bought a drive yet, the Kingston SSDNow V+100 series uses this controller.

    The aggressive garbage collection can help retain performance as the drive becomes cluttered, but can potentially reduce longevity. Flash memory can only be written to so many times before it goes bad, so a lot of garbage collection means extra writes -> reduced lifespan. How much less of a lifespan and if it's something to worry about is something i'm not sure about.

    I've definitely left a wall of text here, but I've got one more bit of advice to configure your system for the ssd, and it's to enable 'noatime'. Unix based systems normally keep track of the last access time of each file, or atime. This timestamp is modified every time a file is read! Imagine if spotlight is indexing your drive and reading every single file - that's going to cause a lot of extra writes as the atime values are changed! Thankfully, atime can be turned off. It's called noatime, and there's a good guide on how to do it here:

    http://blogs.nullvision.com/?p=275

    There's also some other SSD advice there, but I wouldn't bother with the RAM disk thing, as I've read conflicting info about how good of an idea it is.
     
  19. miata thread starter macrumors 6502

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    #19
    Thanks for the info. I just placed my order with OWC.
     
  20. maflynn Moderator

    maflynn

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    #20
    I opted for the OWC drive because of the problems the vertex 2 seems to have issues with MacBook, particularly the 13" MBP. I paid more then I wanted to and while I could have gotten a larger OCZ drive, the peace of mind/excellent customer support that OWC provides is worth it.
     
  21. WMuntean macrumors regular

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    #21
    FYI, I wouldn't be too concerned with the amount of "Free" space on your hard drive. If the issue is maximizing unwritten sectors on the SSD, that goal will become unattainable within several months of use. For example, you can contrast your written data in Disc Activity under OSX's Activity Monitor with the amount of data that you -- the user -- actually modified. Here, you will notice about 500mb of unaccounted data being written by the OS (given that you use the computer for about 4-6 hours a day). That will add up and, regardless of what the OS displays as free space, the sectors on the SSD will be saturated.

    Thats my understanding of the whole "headroom" issue. What are everyone's thoughts on this?
     
  22. miata thread starter macrumors 6502

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    #22
    All of this SSD block wiring business seems very complicated. My understanding is controllers like the SandForce do things to minimize the number of writes that wear out the SSD. When you reduce the amount of free space the conroller has more difficult doing this block write management and starts re-writing blocks at a higher rate. I think that is one of the reason different SSDs have different degrees of over-provisioning.

    I was reading up on this free space stuff and was hoping to find a hard rule at least for specific SSD drives.
     

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