Mac Hardware « Jonathan Mills

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Using RAID 10 on Mac OS X

Wednesday, May 27th, 2009

Now that your raid set is hosed, feel free to experiment with new things. Like a hybrid raid that uses a software RAID 0 to stripe across two hardware RAID 1 mirrors.

First, boot off your Mac OS X install DVD. Open RAID Utility. Use it to create two mirrors. Something like this:

Then, open Disk Utility and play with its software raid features until you make it stripe across those two mirrored volumes you just set up. Like this:

Now install Mac OS X on your new, hybrid, RAID 10, that can handle up to two disk failures (if they aren’t in the same mirror), and doesn’t become degraded in a disk failure scenario, and has very fast rebuild times. win-win-win.

Now, to go out and buy a big external drive to run Time Machine with…..

Posted in Apple, Mac Hardware, Mac OS X | Comments Off

NEVER USE RAID 5. EVER.

Wednesday, May 27th, 2009

So, over a year ago I bought a Mac Pro with the Apple RAID Card. I was really disappointed to find that it didn’t support RAID 10, which is a form of nested raid whereby a RAID 0 (a stripe) is laid across two or more RAID 1’s (disk mirrors). Apple’s implementation allowed for RAID 0+1, which is the other way around: a mirror of two stripe sets usually. That is a much inferior setup, because if any single disk fails, then both disks in that striped pair are out — meaning half your mirror is down. In a RAID 10, you can lose a disk without penalty. You can even lose two disks as long as they aren’t on the same side of the stripe (i.e. aren’t both in the same mirrored pair) — again, without penalty.

In light of Apple’s foolish RAID 0+1 option on their raid card, I opted for RAID 5 instead. Against my better judgement. But with faith in Apple. AND IT FAILED. I lost one disk last week. I promptly shut down my machine in an orderly fashion (because SATA isn’t hot-swappable; only SAS can do that in a Mac Pro). I replaced the failed disk with an identical cold spare that I had on hand (holla). I booted up, I started the RAID Utility program, I marked the new disk a hot spare, the Utility added it back into my raid set and began rebuilding the array, which, of course, was in a degraded state. The rebuild finished — all lights were green — the RAID Utility told me that my RAID 5 set was “Viable (Good)”. Viola! Right?

Wrong. I rebooted the machine and it never came back up! I booted off the Mac OS X DVD and verified the volume in Disk Utility. Fail. Inaccurate record count. Unable to mount the volume. I re-open the RAID Utility and attempt a VERIFY procedure on the raid set. Fail. It won’t even start the routine.

In the end, I lost the entire 1.2 TB RAID 5, with about 600 gigs of my precious data on it. I had backups of all the most recent things, but lost some music, and quite a lot of movies I’d ripped from NetFlix DVD’s and — because of their size mainly — hadn’t backed-up onto my too-small external drive. Yeaaaah. *sigh*

Thanks, Apple.

Posted in Apple, Geek, Mac Hardware, Mac OS X | Comments Off

iPhone 2.0 Worldwide Launch on June 9th

Wednesday, May 21st, 2008

iPhone 2.0 Worldwide Launch on June 9th | Gadget Lab from Wired.com:

A June 9 launch date for the iPhone 2? No surprises there, and now it looks like inside sources are confirming the June 9 date, which is also when Steve Jobs’ keynote at Apple’s Worldwide Developers Conference is scheduled.
But Gizmodo’s Jesus Diaz has got wind of the details of the launch, and his source tells him that the Second Coming will be a worldwide event — not just in the United States. He also claims that his snitch, “someone very, very close to the 3-G iPhone launch”, says that the current fixed pricing model will be discontinued in favor of a more Euro-friendly flexible price point, one that can shift subject to the markets and the whims of the telcos.
The last point concerns Spain. As we reported this morning, Telefónica will indeed carry the iPhone, and will be launching it along with its brand new Madrid megastore on June 18.

Via Wired.com

Posted in Mac Hardware, iPhone | No Comments »

Mac Pro RAID Card not all that ‘Pro’

Friday, March 7th, 2008

Does RAID 0+1 instead of RAID 10. Really? Seriously?

I was contemplating ordering one of these with a Mac Pro because I wanted to use it in RAID 10. RAID 10 is a stripe (RAID 0) across two or more mirrored pairs (RAID 1). Conversely, RAID 0+1 is a mirror across two or more striped pairs. But as the manual clearly states, it doesn’t do RAID 10. It does RAID 0+1, and that’s not so good.

There are dramatic differences between these two configurations:

Chances of array failure:

“Mathematically, the difference is that the chance of system failure with two drive failures in a RAID 0+1 system with two sets of drives is (n/2)/(n – 1) where n is the total number of drives in the system. The chance of system failure in a RAID 1+0 system with two drives per mirror is 1/(n – 1). So, using the 8 drive systems shown in the diagrams, the chance that losing a second drive would bring down the RAID system is 4/7 with a RAID 0+1 system and 1/7 with a RAID 1+0 system.”
Performance in degraded state:

Another difference between the two RAID configurations is performance when the system is in a degraded state, i.e. after it has lost one or more drives but has not lost the right combination of drives to completely fail. In a RAID 0+1 configuration, the loss of any drive in a set causes the failure of that entire set and the set is removed from the RAID system. Generally (in the two set case) this means you are left with a RAID 0 system made up of the remaining set of disks. This probably slightly improves write performance and slightly degrades read performance (but that’s just a WAG, I haven’t done any testing). In a RAID 1+0 system, you would see the same effect on each mirror that loses a drive, but not the whole system. In other words, a RAID 1+0 configuration will tend to show similar, but less dramatic, changes in performance when in a degraded mode than RAID 0+1.
Recovery once a disk is replaced:

RAID 1+0 only has to re-mirror one drive, whereas RAID 0+1 has to re-mirror the entire failed set. So RAID 1+0 will recover significantly faster.

Given these pretty significant failings of RAID 0+1 as compared to RAID 10, it’s a pretty good question as to why Apple would choose the much poorer option for its ‘Pro’ RAID card, for which it charges $720. I’m just really left scratching my head.

Shame on you Apple, shame!

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Time Capsule teardown

Saturday, March 1st, 2008

Time Capsule teardown:

Filed under: Wireless, Apple

Apple’s Time Capsule hasn’t even been shipping for a week yet, and Flickr user “nakedmac” has already dissected his Time Capsule. What may be surprising is that the Time Capsule is no more than an Airport Extreme with a hard drive. But remember when Steve said that the Time Capsule would feature a “server-grade hard drive?” Well, it features a Hitachi Deskstar hard drive. According to the Typical Mac User Podcast blog, the Hitachi hard drive isn’t necessarily rated for “server-grade.”