Halp me trim down my Mac system drive to fit a ssd

April 22, 2011 12:49 PM

SSD's for Mac Pro (NOT a laptop): I'm thinking about adding a smallish one of these to a 3-year-old Quad-Core Xeon desktop and can't find any descriptions about how exactly to split out storage (Documents, Pictures, Mail, Downloads, etc.) from apps and System files. I.e., how to install Snow Leo and apps on the ssd so they use another standard internal drive for all their storage, etc.? Anybody done that? Thank you!
posted by dpcoffin to Computers & Internet (10 answers total)

You want to move your /Users directory to a different partition.

Here's a recent How-to.

If you're still really tight on space, you may want to look into moving swap and logs to another partition. The downside is that they are some of the most-used files, so you may not get as much advantage from your SSD as you're hoping for if you put the files that should be cached on slower drives.
posted by Mad_Carew at 1:00 PM on April 22, 2011

Before moving /Users/, I'd figure out what out of ~/ doesn't fit. Probably just your music, photos and videos. Does anyone really have 40 GB of word docs? Then I'd stick all that extra stuff onto a second harddrive (I've called mine Media) and now my boot drive is tiny enough to fit on a SSD. I'd then CCC my boot drive to the new SSD, replace the boot drive with the SSD and now I'm done. Should take about an hour.
posted by Brian Puccio at 1:05 PM on April 22, 2011

You want to move your /Users directory to a different partition.

Yep, this is the right answer. Make the SSD the boot/app disk and migrate your Users folder to a regular hard drive.
posted by Blazecock Pileon at 1:08 PM on April 22, 2011

I have a setup where a SSD is my boot drive in Snow Leopard, and a 750GB 2.5" drive is my data drive. I did not move /Users/. I moved my iTunes library and everything that is big (video files, software storage etc) onto the 750GB which is mounted as /Volumes/data/. Keeping ~ on your SSD greatly improves browser cache performance and other caches which are kept in ~/Library/. You can easily manually get all of the big stuff out of ~ without moving /Users/ and will see better performance as a result.
posted by thewalrus at 1:37 PM on April 22, 2011

I should add that all kinds of other things will see a big SSD performance improvement from keeping ~ on your boot drive. Google Earth's cache, for example, and a lot of things that keep small files stored under ~/Library/Application Support/. My local copy of my IMAP email is small enough to keep in ~/Library/Mail/ which greatly improves search performance.
posted by thewalrus at 1:41 PM on April 22, 2011

I totally agree with thewalrus. Don't move your home directory in its entirety- move the big stuff.

iTunes prefs will let you specify where your music lives. Launch iPhoto while holding down Option and you can point it at a different database. Mail and Browser downloads can be set via their prefs. Use IMAP for your mail.

Those things alone will likely account for 90%+ of your disk space.
posted by mkultra at 1:50 PM on April 22, 2011

Lots of writes are done to cache folders. Considering the limited write life of SSDs and their relative costs, it might be a good idea to prioritize which cache folders go on the SSD.
posted by Blazecock Pileon at 2:02 PM on April 22, 2011

Response by poster: Interesting idea, Mr. Pileon, altho it sounds a bit over my head…
So how exactly would you figure out which caches work the hardware the hardest, and then safely put some of them one place and leave others where they were?
posted by dpcoffin at 1:41 PM on April 23, 2011

Personally, I wouldn't bother. I'd just keep the /Users folder on a separate platter hard drive.
posted by Blazecock Pileon at 9:32 PM on April 23, 2011

I completely agree with thewalrus and mkultra, you have a few GB of other files that your apps will constantly read from and write to, you're getting a solid state drive to minimize latency, you might as well go all in, it doesn't cost you more.

Lots of writes are done to cache folders. Considering the limited write life of SSDs and their relative costs, it might be a good idea to prioritize which cache folders go on the SSD.

If by "limited write life" you mean "you will no longer be able to write to the drive in several years", then yes, I'd worry. (I don't own a hard drive older than 3 years, spinning or otherwise.)

References?

• Assuming a much smaller endurance rating of 100,000 cycles (typical rating quoted by NAND flash vendors), a bigger volume of writes per day at 3.4TB and no caching nor wear leveling implementations, a 160GB solid state drive is projected to last up to 12.9 years, which is definitely longer than the average replacement cycle of most IT storage devices and equipment.
• With the Eee PC SSD, a typical user (6 hours/day, 10% write rate) will write for 36 minutes per day resulting in a useful lifespan of ~25 years
• Multiply that out and it would take 360,000 days of using my machine the way I have been for the past two weeks for all of my NAND to wear out; once again, assuming perfect wear leveling. That’s 986 years. Your NAND flash cells will actually lose their charge well before that time comes, in about 10 years.
• To give you an idea, the Intel X25-M flash drives claim a lifetime of 5 years even if you average writing 20GB a day, which is far more than most people write every single day for five years.
• I've had an X-25 G2 SSD for almost two years now (snagged one from newegg right as they came out) in my MBP that I use about 50 hours a week as my boot drive with no issues. Recently did the unsupport TRIM enabling and speeds are back up to the same levels as when I purchased it. No signs of writes failing. Besides, when I worry about data integrity, I've got a RAID 6 array that does weekly scrubs with all of my data backed up. Most everything I do on my computer is instant and using a computer with a solid state drive is torture.

posted by Brian Puccio at 8:43 AM on April 25, 2011