On The Extinction Of Ramdisks

System RAM is not typically used for storage anymore

Ramdisks were a cheat to make slow system I/O tolerable, but it was never an easy decision. These days, computers are fast enough that ramdisks are rare. Every part of the computer has gotten quicker and cheaper over the last two decades, including hard disk drives, RAM, and CPUs. A typical laptop like my MacBook Pro might have 4 GB of system RAM, 320 GB of hard disk capacity, and dual 2 GHz CPUs.Those specs would have seemed inconceivable just a few years ago: I still have a Dell laptop with a 20 MHz CPU and two expensive upgrades: 1 MB of RAM and a 20 MB hard drive!

Far more impressive, though, are the numerous performance optimizations that have appeared. I/O channels are quicker than ever, and caches have appeared at most performance bottlenecks. It’s hard to believe, but computers used to rely much more on raw storage. Many hobbyists recall waiting for data to load from cassette tape drives, or that one key performance advance in Intel’s 80486 chip was its on-chip cache. Today’s CPUs have three levels of cache, and operating systems have gotten much better at caching data internally as well.

Hard disk drives have sprouted their own caches, too, making I/O seem quicker than it is. My 1997 Toshiba laptop used an un-cached 4200 rpm hard disk, but even laptop drives today sport 16 MB or more and spin at 5400 rpm or faster. Although RAM was scarce back in the day, the performance gained from a ramdisk was worth the effort. Faster I/O and strategic caching has largely eliminated this need. Increasing operating system intelligence also plays a major part – witness the failure of hybrid hard drives.

The Modern Use Case

A long-standing argument in the field of computer system performance revolves around whether to manually reserve resources and place data or to let the system dynamically manage resources on its own. Computers do a decent job if allowed to, often adapting quicker and more efficiently to changing demands. But some jobs are harder to automate, and buffers and caches don’t always catch the right data.

Purely temporary data can be written to a ramdisk as a high performance scratch space. There is no need to store this on disk at all, and merely placing it there is likely to “pollute” the buffers, pushing out real useful data.

A ramdisk can also increase security somewhat by never allowing certain data to be written to disk. Ramdisks are sure to be flushed on the next reboot, but data on disk can linger and be discovered later.

One could even argue that today’s high-performance solid state disk is simply an evolution of the old ramdisk concept. NAND flash and RAM both offer the high random performance of the ramdisks of yore, and many analysts expect them to displace high-performance hard disk drives in the coming years. So perhaps ramdisks are not extinct after all!

Ultra-performance storage systems like this Violin array use RAM for storage

Using Ramdisks In Mac OS X

Mac OS X has the ability natively to create and use ramdisks. Here’s the simple procedure:

1. Create the ramdisk with hdiutil – This terminal command will create a 1 GB ram disk and report the name used. The number following the “ram://” statement is a number of 512 KB disk blocks – multiply the desired ram size in MB by 2048 (that’s 1024 times 2) to derive other sizes.
   hdiutil attach -nomount ram://2097152
2. Format the ramdisk with diskutil – The next command will format the newly-created ramdisk using the diskutil tool. We will use /dev/disk3, but you should specify whatever disk device hdiutil reported from step 1. You can also specify a different filesystem or disk name.
   diskutil eraseVolume "HFS+" "ramdisk" /dev/disk3
3. Your ramdisk will now appear – OS X will now mount the newly-created ramdisk and it will appear on your desktop. Note that the contents will be destroyed if it is unmounted or if the operating system is rebooted!
4. Delete your ramdisk – It’s worth saying once again: The ramdisk will disappear and all data will be deleted when you eject it or power off your computer. Be sure to back up any important data from it, then eject it with the following command:
   hdiutil eject /Volumes/ramdisk

Script It!

My backup script called for the creation of a tar file, compression, encryption, and rsync copying. I decided that I could perform the first three functions on the ramdisk to increase performance and reduce the chance that an unencrypted version would remain on the disk if the script failed.

A simple command line combination of the above creates the necessary ramdisk:

diskutil eraseVolume "HFS+" "ramdisk" `hdiutil attach -nomount ram://2097152`

This failed once I put it in a shell script, however. The issue was the finicky nature of diskutil – hdiutil’s output included a number of whitespace characters, and diskutil failed in the script whenever it encountered this. So I used the cut command to grab just the first field of the output, like so:

diskutil eraseVolume "HFS+" "ramdisk" `hdiutil attach -nomount ram://2097152 | cut -d " " -f 1`

This solved my problem, and I was able to tar and compress to /Volumes/ramdisk in my script. I added the hdiutil eject command to the script right after the encryption step to wipe out the unencrypted data. Although this isn’t foolproof security by any means, it’s better than nothing.

© sfoskett for Stephen Foskett, Pack Rat, 2010. | Ramdisks: Back From the Brink of Extinction
This post was categorized as Apple, Computer History, Enterprise storage, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

Here’s the scoop: Apple’s Mac mini EFI Firmware Update 1.2, released back at the end of August, claimed to improve “compatibility with the latest Apple memory kits on Mac mini computers”, but in typical Apple fashion, no one quite knew what that meant. Some brave soul must have tried installing two 4 GB PC3-8500 SO-DIMM modules in the Mini’s two RAM slots, and must have been awfully happy when they did, because it works! All 2009 Mac Minis are supported, including the recently-released Mac Mini Server and the earlier March-era machine.

This is now confirmed by Mac Mini Colo, a more reliable source than Macrumors forum posters, so I’m finally confident in posting this. Being a cheapskate, I’m not going to run out and spend $510.98 at Amazon on two Crucial SO-DIMMs for my $599 computer. But I’m eager to hear from you if you have the inclination, and will be watching as prices fall in the box at right. An 8 GB Mac Mini ought to perform amazingly when running VMware Fusion or VirtualBox!

Note: Some of these links include affiliate codes that help pay for this blog. For example, buying an Amazon Kindle with this link sends a few bucks my way! But I don't write this blog to make money, and am happy to link to sites and stores that don't pay anything. I like Amazon and buy tons from them, but you're free to buy whatever and wherever you want.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | Got Excess Money? Upgrade Your 2009 Mac Mini RAM To 8 GB!
This post was categorized as Apple, Terabyte home. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

Can you supercharge a Mac Mini?

Last week I reported my progress upgrading my Mac Mini’s RAM and hard drive to extract much more performance out of Apple’s little desktop. And indeed, adding a 7200 rpm high-performance laptop hard drive did make a noticeable difference in system responsiveness.

But a question came in via email asking, will Western Digital’s killer 10,000 rpm VelociRaptor SATA drive work in the Mac Mini? So inspired, I set out to find out just how far one can push a Mac Mini’s performance!

Pillars of Performance

As I noted in my last update, there are four keys to desktop system performance: CPU, RAM, storage, and graphics. The Mac Mini’s CPU is soldered in place and its graphics are integrated into the system chipset, so neither are upgradable. The best one can do on the CPU side is to order a built-to-order 2.26 GHz Mac Mini from Apple, adding $150 to the base Mac Mini price of $599.

Base Mac Mini: $599

2.26 GHz CPU upgrade: $150

Running total: $749

PC hackers commonly upgrade their systems’ performance by tweaking the system BIOS to overclock the CPU, memory, and system bus. But you can’t overclock a Mac Mini, or at least I haven’t found the secret yet.

More RAM always helps, but the Mini won’t accept more than 4 GB 8 GB of RAM. The graphics can also be improved slightly by installing more than 1 GB of RAM because the system will then use 256 MB of RAM as a frame buffer instead of 128 MB. Since we’re going to be opening the system anyway, we can save some money by upgrading the RAM ourselves. The Mac Mini uses 204-pin DDR3 SO-DIMMs rated at PC3-8500 (1066 MHz). A nice 4 GB matched set can be purchased from Amazon.com for $60.

4 GB RAM upgrade: $66

Running total: $815

Your Apple Mac Mini is now maximally configured, with the exception of storage.

Update: The 2009 Mac Minis can now accept 8 GB of RAM!

Killer Storage

The only remaining upgrade is storage. And here, the Mac Mini is amazingly adaptable. About 2/3 of the vertical space covered by that aluminum and plastic exterior consists of a black plastic cage containing the DVD SuperDrive, hard disk drive, and cooling fan and serving as a support for the BlueTooth and 802.11 wireless antennas. This is your target.

The Mac Mini’s storage subsystem is up to date, with two SATA channels supporting 3 Gbit speed and advanced capabilities like native command queueing (NCQ) even though the stock Mini’s hard drive lacks these features.

The hard drive sits in a cradle immediately under the optical drive, face-up in an open cavity over the motherboard. Although it ships with a slim 9.5 mm high hard disk, my ruler says that the Mac Mini cradle can accept a 12.5 mm z-height disk. This is interesting from a capacity standpoint, since some higher-GB drives are 12.5 mm 3-platter units, including the popular TravelStar 5k500 drive from Hitachi.

However, the Mini was designed to have an air gap between the hard disk and DVD drive, and a 12.5 mm drive will press against the optical unit, potentially causing heat problems. And a larger 2.5″ drive will not fit, including the 15 mm mechanism from the Western Digital VelociRaptor.

Therefore, any crazy disk drive dreams that also include leaving the Mini and its DVD drive in the original case are right out. All is not lost, however! Apple kindly included the MacBook Air’s Remote Disc support, so the Mini doesn’t need a DVD drive at all if you happen to have another Mac or PC handy. Removing the SuperDrive leaves room for up to two 2.5″ hard disks!

Without the SuperDrive in the way, a 2.5″ Western Digital VelociRaptor hard disk drive should fit just fine. Although it ships with a massive heat sink, the VelociRaptor isn’t as power-hungry or hot as you might imagine. It might be a good idea to apply some cooling fins or add an extra fan, but I’m betting the Mini wouldn’t have any trouble driving this 10,000 rpm drive once the SuperDrive is removed. So the WD VelociRaptor is a serious option for the Mac Mini.

Another killer performance option is a RAID-0 set of internal SATA drives. Although the Mini’s second SATA channel (normally used for the DVD drive) does not have the proper connectors or mounting supports for a hard disk drive, iFixit sells a DIY kit to connect a second hard drive. This kit, which includes two 500 GB 5400 rpm hard drives, sells for about what a single 300 GB VelociRaptor costs, and should provide similar performance using RAID-0 striping.

WD 300 GB VelociRaptor hard disk or iFixit dual-500 GB kit: $250

Running total: $1,065

Conclusion

So there you have it! For just over $1,000, you can have the baddest Apple Mac Mini possible. But for quite a bit less, I suspect that a 2.0 GHz/4 GB/7200 rpm disk combo would be nearly as fast.

One more thing: If you decide to use RAID-0 on your internal drives, you must use Time Machine to protect your data! A stripe set of disk drives poorly mounted in a tiny chassis without a properly-engineered cooling or power system is a recipe for disaster. Your disks will fail, and your data will be lost!

Note: Some of these links include affiliate codes that help pay for this blog. For example, buying an Amazon Kindle with this link sends a few bucks my way! But I don't write this blog to make money, and am happy to link to sites and stores that don't pay anything. I like Amazon and buy tons from them, but you're free to buy whatever and wherever you want.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | How Far Can You Push a Mac Mini?
This post was categorized as Apple, Terabyte home. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

The Tortoise and the Hare: Upgrading my new Mac Mini's hard drive and RAM made all the difference!

It may seem odd to buy a computer intending to upgrade it right out of the box, but so it was with me when I snapped up a new 2009 Nvidia-powered Mac Mini. I had been waiting for Apple to update the aged Mini line, saving up my pennies, but the out-of-box specs for RAM and hard drive space were underwhelming.

Out-Of-Box Upgrade

Unlike the old Mini, where the $799 model netted a SuperDrive as well as additional memory and disk, the new Mini’s $200 upmarket model was seriously overpriced. So I decided to pick up a base model and upgrade it myself right away.

Now that my upgrade is complete, I’m pleased to say that my Mac Mini is a whole new animal! Where the spec base Mini was sluggish, exhausting its meager 1 GB of RAM and swapping to a crazy slow hard drive, my Mini is now snappy and quick. Launching iTunes (with 13,000 songs) took upwards of 30 seconds before, but the song list is now visible before the dock icon bounces twice!

Desktop computer performance is a product of four variables:

1. CPU speed
2. RAM capacity
3. Hard drive performance
4. Graphics capabilities

Other things matter a great deal, but only these four can be changed in a given system. In other words, although the chipset, memory speed, and system bus all have a massive impact on overall performance, you can’t swap these things out! The majority of computers are limited to upgrades in the four areas listed (CPU, RAM, hard drive, graphics), and each must be balanced for satisfying system performance.

Apple designed the Mac Mini as an integrated unit, however, so the graphics and CPU are not upgradable. But these are the system’s strong suits: The Nvidia 9400M chipset gives solid graphics performance, matching or beating the integrated Nvidia 8600M GT graphics in my late-2007 MacBook Pro, and the Intel Core 2 Duo CPU is easily quick enough for general computing tasks. Frustratingly, Apple ships the Mac Mini with inadequate RAM and a very, very slow disk. So upgrading both is a sure-fire way to an excellent system!

Good Memories

Update: The 2009 Mac Minis can now accept 8 GB of RAM!

Killer Storage

The Nvidia chipset is up to date as far as RAM goes. The Mini uses fast 1,066 MHz DDR3-8500 memory and has two SO-DIMM slots. These chips are still hard to find in stores (Fry’s doesn’t carry them!) but they aren’t expensive. Thankfully, rather than filling up both slots with useless 512 MB parts, Apple uses a single 1 GB SO-DIMM in base Minis. I was lucky enough to find another Mini upgrader on Twitter who sent me his leftover RAM for the cost of shipping after taking his Mac all the way to 4 GB (thanks, Joe!) and I bet that most folks could do the same. Otherwise, Other World Computing sells leftover 1 GB DDR3-8500 SO-DIMMs from aluminum MacBooks and Mac Minis for just $12.95! They also have upgrade instructions.

The new Mac Mini performs well in CPU and RAM tests, but 1 GB is insufficient and upgrading to 2 GB gives a noticeable boost

As of Friday, my Mini was rocking 2 GB of RAM, enough for general desktop computing. One side benefit of upgrading was graphics performance: The Mini will use 256 MB of system RAM as a frame buffer if at least 2 GB of RAM is installed, speeding up user interface windowing operations by about 20%, according to Xbench. Overall memory performance also improved with two SO-DIMMs installed, with streaming operations up by 20% to 25%.

Driving It Home

The Mini’s hard drive performance was especially disappointing. The stock 120 GB Hitachi TravelStar 5K320 was a special Apple OEM unit with a single platter and 8 MB of cache. Its slow 1.5 Gb SATA interface wasn’t the bottleneck, though – this drive just poked along, maxing out at about 35 MB/s in sequential operations. This compares favorably to previous-generation drives, but can’t hold a candle to the latest disk drive mechanisms. Apple’s upgrade option for the new Mac Mini is a 320 GB 2-platter version of this same drive. I expect it will perform only slightly better than the 120 GB unit. The stock 320 GB drive seems to perform much, much better than the 120 GB unit in sequential operations!

I decided to upgrade my Mini to a 7200 rpm high-performance drive, and my research led me to Hitachi’s 7k320 series. With just two platters, this 9.5 mm high drive unit remains slim enough for the Mini (or any laptop), and the power specs look great! Hitachi claims only a half-Watt difference between the 7k320 and miserly 5k320 in spin-up and negligible differences in most other operations. Comparison tests showed that the Hitachi was a solid performer against competing offerings from Western Digital, Seagate, and Samsung, and ZipZoomFly listed the 320 GB drive for just $59 after rebate!

The 7200 rpm Hitachi is almost twice as fast as the stock Mac Mini hard disk in random I/O operation

I couldn’t be happier with the 7200 rpm Hitachi drive’s performance. It blows away the stock drive, delivering 32 MB/s in large random write operations, and even beats the solid 5400 rpm Western Digital Scorpio Blue drive I use in my MacBook Pro.

The 7200 rpm Hitachi is easily the fastest drive I've tested in sequential reads and writes

The new Hitachi blows everything else away in sequential operations, too. It delivers a solid 80 MB/s while reading and writing large files while the stock unit could barely reach 35 MB/s! These differences are magnified by the 7k320′s large 16 MB cache, which makes the most of its 3 Gb SATA interface.

Although it doesn’t have to conserve battery power like a laptop, heat is a major concern in a small computer like a Mac Mini, and disk drive power requirements translate directly into heat generation. It turns out that the Mini has such an excellent cooling system that I thought Bjango’s iStat Server was broken: It almost always reported 1,500 rpm fan speed and 120-130° F temperatures. Under sustained load, the Mini’s fan never reached 2,000 rpm and no sensor reported greater than 150° F. The 7200 rpm Hitachi drive has had no impact on in-box temperature or noise levels.

The Mac Mini: Transformed!

Apple delivered a solidly-designed general-purpose desktop computer with the new 2009 Mac Mini, but crippled its performance with too little RAM and a too-slow hard drive. In short, Apple failed to balance the four key pillars of computer performance!

The relatively simple task of upgrading the RAM and hard disk drive transforms the Mac Mini: In normal operations, the upgraded Mini is easily two or three times as responsive as the stock machine! My total cost (for the Mini, the RAM, and the hard drive) was $701. Apple’s $799 2 GB RAM/320 GB disk Mac Mini may look similar on paper, but it won’t touch mine in terms of disk performance. I could have gone all the way to 4 GB of RAM for less than the remaining $98 price difference.

One final word: Apple assured MacWorld that they will continue to honor their warranty on upgraded machines as long as nothing is damaged in the process. The Mac Mini is not that difficult to work on, as long as you have proper tools. Use a static strap, be careful with internal the wires and connectors, and take your time. Once upgraded, the Mac Mini is a satisfying desktop or home server.

Interested in building a home server with Apple’s Mac Mini? Watch my blog over the coming months for detailed reports like this one covering setting up iTunes for whole-house audio, integrating Roku’s SoundBridge music systems, serving video to a TiVo, and configuring Mac OS X as a home server. I’ll also be experimenting with Microsoft’s Windows Home Server and VMware ESX on the new Mini!

© sfoskett for Stephen Foskett, Pack Rat, 2009. | Upgrades Give New Mac Mini a Whole New Attitude
This post was categorized as Apple, Terabyte home. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.