7 ms·

Mac OS X SSD tweaks

62 points by bensummers 17y ago

wmf 17y ago
IMO these go beyond tweaks and are more like SSD ricing.
- Nwallins 17y ago
  noatime is a great counterexample to your 'ricing' claim. I run this mount option on nearly every filesystem under my command. relatime is also a viable option if you need things like mutt. From http://kerneltrap.org/node/14148 http://kerneltrap.org/node/14148 (which discusses relatime, a less-drastic version of noatime that keeps mutt working) > Ingo Molnar stressed the significance of fixing this performance issue, "I cannot over-emphasize how much of a deal it is in practice. Atime updates are by far the biggest IO performance deficiency that Linux has today. Getting rid of atime updates would give us more everyday Linux performance than all the pagecache speedups of the past 10 years, _combined_." > "It's also perhaps the most stupid Unix design idea of all times. Unix is really nice and well done, but think about this a bit: 'For every file that is read from the disk, lets do a ... write to the disk! And, for every file that is already cached and which we read from the cache ... do a write to the disk!'"
- mbreese 17y ago
  What's the issue really? There are three things mentioned, none of which is very controversial (okay, so part of the last one is). * noatime - which is a standard setting on Linux these days * Remove the hibernate file - which is valid, if you know the tradeoffs. And the author does describe them sufficiently. * Move temporary files to ramdisks - this is a pretty common speedup too. The controversial part is what to put in the ramdisk.
DenisM 17y ago
Sadly, no performance data is provided.
- Luyt 17y ago
  But these are not tweaks to optimize performance - they're for reducing the number of writes to the SSD somewhat. Now that I think of it, one could indeed view those writes as a performance metric (better being: less writes).
  - DenisM 17y ago
    Is it really better, or is it just a fell-good thing? What if reducing number of writes has no practical consequences at all? There is no data provided to judge either way.
    - scott_s 17y ago
      Cells in an SSD have a finite number of writes. But some brief Googling convinced me that with current drives, the number of writes a cell can take is not a concern even for heavy use.
    - lanaer 17y ago
      When an SSD modifies a page, it has to erase & rewrite the entire block. SSDs try to avoid this by marking the block as “free” and writing data to an entirely different block, if one is available. The point here is that in order to write a tiny bit of data, SSDs have to write to a larger portion of the drive (usually). So reducing the # of tiny writes should lengthen the lifetime of the drive. It's theory, but the theory is sound enough to me to optimize for it if there's little or no downside to the optimizations. Edit: though, as noted elsewhere, these drives will generally last more than long enough, so the effort is probably unnecessary.
- barredo 17y ago
  Here's a link to a more recent post in other blog http://damieng.com/blog/2010/04/09/macbook-pro-upgrade-to-crucial-256gb-ssd http://damieng.com/blog/2010/04/09/macbook-pro-upgrade-to-cr... — Author switched original 320GB MacbookPro HDD with a Crucial 256GB SSD, it provides benchmarks and compared perfomance and an interesting points: Don’t go with Apple’s factory-options for an SSD as they use slower Samsung drives and charge a premium for it which is unacceptable especially given how easy they are to replace. Which I hope, if true, Apple will fix by adding high-end SSD options in the near future
uuid 17y ago
Another way to save (the oh so precious) space on SSDs is to apply HFS+ compression to files.You can use ditto(1) or this GUI: http://latenitesoft.com/squeeze/ http://latenitesoft.com/squeeze/ Note, however, that files are decompressed on writes, so don't try it on anything large and frequently written to.
sumeeta 17y ago
Is there really a serious issue in the way OS X handles SSDs? I think I want to replace my MacBook’s hard disk with an SSD, but I’m afraid of having to spend hours rigging out the best configuration. Do you have to play with settings if you order a Mac from Apple with an SSD pre-installed? It seems like if I want to just plug an SSD in and get on with my life, I’ll have to wait for an OS X update. Unless this is all just PC-ricer talk that’s safe to ignore…
- uuid 17y ago
  As long as you leave plenty of free space, SSDs work great out of the box. Don't ever fill them (something beyond 80% capacity), or you will crush performance. The tweaks in the article are attempts to optimize for the last 2%, but in no way necessary.
  - rufo 17y ago
    Since you're going to be reading and writing to the drive repeatedly, the drive is always going to hit the write performance crunch no matter what you do (unless you support TRIM - Windows 7 does with the correct drivers, OS X does not, not sure about Linux). However, even degraded, write performance of a modern SSD will still make a hard drive look like yesterday's news - so honestly, I wouldn't even worry about it at all.
    - uuid 17y ago
      SSDs do degrade by around factor ten (!) in write performance when full, although not in read performance. (Tested this with an x25-m). Sadly, recovering from a fragmented SSD on OSX right now involves opening the machine and booting linux. (I tried that, and it works: http://forums.macrumors.com/showthread.php?t=841182 http://forums.macrumors.com/showthread.php?t=841182)
      - kwyjibo 17y ago
        My X25-m died after 3 months of use, and I had the hd nearly full.. And I thought I would have never have to make backups again ;)
rufo 17y ago
Given that Intel SSDs are claimed to support writing 100GB of data every day for five years before losing the ability to write, and I rarely hit even 10GB written in a bus development day according to OS X's Activity Monitor, I'm uncertain if these tweaks will make all that much of a difference in the lifespan of the drive.
- mrkurt 17y ago
  It's not so much the lifespan, it's performance degradation after lots of the drive has been written to. It's not a permanent problem, but I know lots of people who notice and end up formatting to regain their performance.
  - cdr 17y ago
    As far as I'm aware, TRIM takes care of the performance degradation. Not sure that OSX supports TRIM yet though.
    - wmf 17y ago
      Or it would if OS X supported it.
    - WALoeIII 17y ago
      OS X does not support TRIM. TRIM is only enabled on the G2 Intel SSDs and newer competing models, the original G1 does not have the instruction.
      - blasdel 17y ago
        And using a drive firmware that expects TRIM results in a massive regression when the kernel isn't regularly telling it to trim blocks, as it disables its normal GC. The Intel GC algorithm was great. I would have preferred it if they had simply ignored all the 'power user' fanboys that constantly harp on about how it would somehow save the day. Let them buy other drives, and leave more for the rest of us.
jawn 17y ago
For those like me who came away from this wondering what windows tweaks were available, I found a good thread here: http://www.ocztechnologyforum.com/forum/showthread.php?47212-Vista-32-64-SSD-Windows-Registry-tweaks http://www.ocztechnologyforum.com/forum/showthread.php?47212... It is a lot of the same types (ramdrives, no hibernation) of changes but for windows users.

Mac OS X SSD tweaks

62 points by bensummers 17y ago

wmf 17y ago

IMO these go beyond tweaks and are more like SSD ricing.

Nwallins 17y ago
noatime is a great counterexample to your 'ricing' claim. I run this mount option on nearly every filesystem under my command. relatime is also a viable option if you need things like mutt. From http://kerneltrap.org/node/14148 http://kerneltrap.org/node/14148 (which discusses relatime, a less-drastic version of noatime that keeps mutt working) > Ingo Molnar stressed the significance of fixing this performance issue, "I cannot over-emphasize how much of a deal it is in practice. Atime updates are by far the biggest IO performance deficiency that Linux has today. Getting rid of atime updates would give us more everyday Linux performance than all the pagecache speedups of the past 10 years, _combined_." > "It's also perhaps the most stupid Unix design idea of all times. Unix is really nice and well done, but think about this a bit: 'For every file that is read from the disk, lets do a ... write to the disk! And, for every file that is already cached and which we read from the cache ... do a write to the disk!'"
mbreese 17y ago
What's the issue really? There are three things mentioned, none of which is very controversial (okay, so part of the last one is). * noatime - which is a standard setting on Linux these days * Remove the hibernate file - which is valid, if you know the tradeoffs. And the author does describe them sufficiently. * Move temporary files to ramdisks - this is a pretty common speedup too. The controversial part is what to put in the ramdisk.

DenisM 17y ago

Sadly, no performance data is provided.

Luyt 17y ago
But these are not tweaks to optimize performance - they're for reducing the number of writes to the SSD somewhat. Now that I think of it, one could indeed view those writes as a performance metric (better being: less writes).
- DenisM 17y ago
  Is it really better, or is it just a fell-good thing? What if reducing number of writes has no practical consequences at all? There is no data provided to judge either way.
  - scott_s 17y ago
    Cells in an SSD have a finite number of writes. But some brief Googling convinced me that with current drives, the number of writes a cell can take is not a concern even for heavy use.
  - lanaer 17y ago
    When an SSD modifies a page, it has to erase & rewrite the entire block. SSDs try to avoid this by marking the block as “free” and writing data to an entirely different block, if one is available. The point here is that in order to write a tiny bit of data, SSDs have to write to a larger portion of the drive (usually). So reducing the # of tiny writes should lengthen the lifetime of the drive. It's theory, but the theory is sound enough to me to optimize for it if there's little or no downside to the optimizations. Edit: though, as noted elsewhere, these drives will generally last more than long enough, so the effort is probably unnecessary.
barredo 17y ago
Here's a link to a more recent post in other blog http://damieng.com/blog/2010/04/09/macbook-pro-upgrade-to-crucial-256gb-ssd http://damieng.com/blog/2010/04/09/macbook-pro-upgrade-to-cr... — Author switched original 320GB MacbookPro HDD with a Crucial 256GB SSD, it provides benchmarks and compared perfomance and an interesting points: Don’t go with Apple’s factory-options for an SSD as they use slower Samsung drives and charge a premium for it which is unacceptable especially given how easy they are to replace. Which I hope, if true, Apple will fix by adding high-end SSD options in the near future

uuid 17y ago

Another way to save (the oh so precious) space on SSDs is to apply HFS+ compression to files.You can use ditto(1) or this GUI: http://latenitesoft.com/squeeze/ http://latenitesoft.com/squeeze/ Note, however, that files are decompressed on writes, so don't try it on anything large and frequently written to.

sumeeta 17y ago

Is there really a serious issue in the way OS X handles SSDs? I think I want to replace my MacBook’s hard disk with an SSD, but I’m afraid of having to spend hours rigging out the best configuration. Do you have to play with settings if you order a Mac from Apple with an SSD pre-installed? It seems like if I want to just plug an SSD in and get on with my life, I’ll have to wait for an OS X update. Unless this is all just PC-ricer talk that’s safe to ignore…

uuid 17y ago
As long as you leave plenty of free space, SSDs work great out of the box. Don't ever fill them (something beyond 80% capacity), or you will crush performance. The tweaks in the article are attempts to optimize for the last 2%, but in no way necessary.
- rufo 17y ago
  Since you're going to be reading and writing to the drive repeatedly, the drive is always going to hit the write performance crunch no matter what you do (unless you support TRIM - Windows 7 does with the correct drivers, OS X does not, not sure about Linux). However, even degraded, write performance of a modern SSD will still make a hard drive look like yesterday's news - so honestly, I wouldn't even worry about it at all.
  - uuid 17y ago
    SSDs do degrade by around factor ten (!) in write performance when full, although not in read performance. (Tested this with an x25-m). Sadly, recovering from a fragmented SSD on OSX right now involves opening the machine and booting linux. (I tried that, and it works: http://forums.macrumors.com/showthread.php?t=841182 http://forums.macrumors.com/showthread.php?t=841182)
    - kwyjibo 17y ago
      My X25-m died after 3 months of use, and I had the hd nearly full.. And I thought I would have never have to make backups again ;)

rufo 17y ago

Given that Intel SSDs are claimed to support writing 100GB of data every day for five years before losing the ability to write, and I rarely hit even 10GB written in a bus development day according to OS X's Activity Monitor, I'm uncertain if these tweaks will make all that much of a difference in the lifespan of the drive.

mrkurt 17y ago
It's not so much the lifespan, it's performance degradation after lots of the drive has been written to. It's not a permanent problem, but I know lots of people who notice and end up formatting to regain their performance.
- cdr 17y ago
  As far as I'm aware, TRIM takes care of the performance degradation. Not sure that OSX supports TRIM yet though.
  - wmf 17y ago
    Or it would if OS X supported it.
  - WALoeIII 17y ago
    OS X does not support TRIM. TRIM is only enabled on the G2 Intel SSDs and newer competing models, the original G1 does not have the instruction.
    - blasdel 17y ago
      And using a drive firmware that expects TRIM results in a massive regression when the kernel isn't regularly telling it to trim blocks, as it disables its normal GC. The Intel GC algorithm was great. I would have preferred it if they had simply ignored all the 'power user' fanboys that constantly harp on about how it would somehow save the day. Let them buy other drives, and leave more for the rest of us.

jawn 17y ago

For those like me who came away from this wondering what windows tweaks were available, I found a good thread here: http://www.ocztechnologyforum.com/forum/showthread.php?47212-Vista-32-64-SSD-Windows-Registry-tweaks http://www.ocztechnologyforum.com/forum/showthread.php?47212... It is a lot of the same types (ramdrives, no hibernation) of changes but for windows users.