320GB striped array (RAID 0) in a Macbook Pro

Macbook Pro with 2 drives installed
**UPDATE: April 2009** Two Intel X25-M 160GB SSDs in striped array in unibody MacBook Pro

**UPDATE: 28 Sep 2008** New benchmarks for striped SSD array in Macbook Pro.

Today, I installed an MCE OptiBay Hard Drive (a second 160GB 5400rpm drive) into my Macbook Pro. The directions that came with the drive were simple to follow, and it took about 15 minutes install (requiring the removal of 20-25 screws, plus two ribbon connectors).

When I booted back up, Mac OS X recognized the drive immediately (a SAMSUNG HM160JC) and asked me if I wanted to initialize it.

Instead, I rebooted from an external drive (backed up by the excellent SuperDuper) and created a striped RAID 0 array using the two internal Macbook Pro drives.

At this point, I discovered that you cannot partition a Mac OS X software RAID volume, so I was stuck with a single, 297.46GB volume. I back up my volumes with SuperDuper, and will just have to create scripts that backup a bootable system copy without images or video (and I'll back up images/video separately, which is fine).

Shown here before the 2nd drive was installed. Installation requires the removal of 25 screws.

I ran Xbench on my system, and the results [download] are pretty impressive. My machine's results are in the first column, compared to results of comparable configurations pulled out of the Xbench comparison site. The last column features benchmarks from a Mac Pro with a 250GB 7200rpm 3.5" drive.

    Macbook Pro Core2
2x160GB 5400rpm
3GB / v10.4.9
RAID 0 (Striped)
Macbook Pro
160GB 5400rpm
2GB / v10.4.9
Macbook Pro
160GB 7200rpm
2GB / v10.4.9
Mac Pro Quad
250GB 7200rpm
4GB / v10.4.8
Seagate 3.5"
  Blocks Score MB/sec Score MB/sec Score MB/sec Score MB/s
Results   137.52   110.50   118.20   158.46  
Disk Test   67.08   36.37   42.94   69.46  
--Sequential   93.51   70.23   77.31   94.80  
---- Write 4K 163.43 100.34 69.63 42.75 97.99 60.16 70.50 43.28
---- Write 256K 139.48 78.92 73.79 41.75 86.30 48.83 104.05 58.87
---- Read 4K 43.68 12.78 57.35 16.78 51.03 14.94 100.62 29.45
---- Read 256K 151.59 76.19 86.17 43.31 96.58 48.54 118.22 59.41
--Random   52.30   24.54   29.73   54.80  
---- Write 4K 23.24 2.46 8.99 0.95 9.68 1.03 21.29 2.25
---- Write 256K 100.03 32.02 37.83 12.11 83.38 26.69 122.85 39.33
---- Read 4K 71.24 0.50 66.16 0.47 89.59 0.63 93.70 0.66
---- Read 256K 106.25 19.72 98.17 18.22 123.23 22.87 138.64 25.73

All reads and writes are uncached.

The results are impressive, except that the RAID 0 doesn't seem to like small-block (4k) reads. Both sequential and random reads performed poorly. This should be fine, as I'm most often working with large images and video files.

screws removed during install

160GB 5400rpm drives are supposed to become much faster as they fill up. My drives are about 30% full, and I plan to re-run the test when they become more full.

MCE reports that the drive is supposed to shorten battery life on the system by 10-15%, but I haven't had a chance to do my own tests.

As for sound, I can hear the 2nd drive now, spinning quietly on the right-hand side of the machine. It's audible, but not annoying. The replacement drive chassis doesn't have the same clip receptacles that the SuperDrive chassis has, so the keyboard top on my Macbook Pro no longer sits exactly flush on the right side. There's probably a 1mm gap, which isn't enough to really bother me.

1mm gap between keyboard and chassis on right side

Subjectively, the system feels more snappy, and I'm happy to have made the upgrade. I use up at least 20-30GB per week in the field, and it will be great to be able to work on my notebook without having an external drive chained to it.

Many people don't like using RAID 0 arrays because they double the likelihood of catastrophic failure; I back up my data all the time -- even when I'm traveling -- so I'm not so worried.

Also see:

- Seagate Momentus 7200rpm 160gb drive benchmarks on BareFeats.com    a single-drive upgrade for better disk performance


This machine is really much faster now. I just booted up Windows XP in Parallels, and it didn't do the usual "take the computer down for a bit" routine during XP startup. It just booted, and was fast immediately after boot, as it is on my Mac Pro. Normally, the XP load process in Parallels slows my entire machine down as it struggles to pull data from the disk.

My Macbook Pro has always run hotter than my old Thinkpad did. Even when doing simple web surfing or writing e-mails, I can't use the machine in my lap for long periods of time without putting a book or pillow between it and my crotch. It *seems* to run a bit warmer with the 2nd drive in, but it's hard to remember, in comparison. The left palm area was always much hotter than the right (make sense -- it's where the main drive is); now the right side is also a bit warm -- but nowhere near the warmth of the main drive area.

The metal strip above the keyboard is always hot, now. I don't remember if this was the case before I put in the 2nd drive. It could also be because it has suddenly become warm here in the Bay Area. The temperature in my loft has gone up by a lot in the past two days.

The internal cooling fans do not run any louder or more often than they used to.


Some folks on the second Digg page are saying that it's stupid to use RAID 0 in a computer, because there are "no real world benefits" and because it's too dangerous.

I disagree. My machine is clearly running much faster, and it doesn't seem to be running that much hotter. The fans still only spin up with high CPU usage. Battery life has always sucked on the Macbook Pro, and the estimates of losing 10-15% seems to be accurate so far. When I copy images onto the machine while in the field, they are simultaneously copied to an external volume for backup. Finally, I back up frequently onto bootable, external media, even when I'm on the road, so losing my internal volume wouldn't be catastrophic. At home, my system backs up automatically to NAS every night. The only problem is that I would have to work off of an external drive, if the RAID failed. I'd have the same problem even if I wasn't using RAID.

I used to use a Thinkpad T-series notebook, which was a great machine because it allowed the use of two hard disks at a time in a supported, modular way. I loved that thing.

Anyway, back to the topic at hand. I'd love to hear about the negative Digg commenters' personal experiences with running RAID 0 in a notebook. I'll bet none of them have ever done it, and are speaking without any facts to back up their claims.


Still going strong! I noticed that I now get bursts of up to 54MB/s when copying over gigabit from my Mac Pro (which is configured in RAID 1+0 over 6 disks). That is awesome.

---UPDATE, NOV 25, 2007---

I have had network copy bursts of up to 90MB/s to my Mac Pro via gigabit ethernet, and regularly sustain 65MB/s when copying large files. See a screenshot here. I can't wait until solid-state drives come down in price. If compatible, I want to shove two of them into my computer and RAID them. :)