SSD vs RAM Disk

[iamcheerful]

Given that SSDs are all the rage these days, be it in portables or desktops, I just want to ask for the opinions of our mac community how do these 2 perform.

I'll likely do a simple perception test with my pb3400c/200 & 240 MHz vs the early 2008 Mac Pro (unfortunately, no SSD equipped yet)

It won't be a totally objective test, as far as possible I want to try to do a realworld kind of test. That said, I'll be disabling Flash or maybe even all plug-ins. However will retain Java & Java script settings.

I was kinda disappointed Apple didn't continue their RAM Disk trick with OS X (RAM is so cheap now, think of what we can do with a 16 GB Bootable RAM Disk!)

Still recall the days where I run my pb3400 on RAM. She was so quiet and can last at least 4.5 hrs on a single battery charge. Writing on such a machine is so nice as it is rather cool and no noise.

[300D]

Apple does have a RAM disk, they just don't make it as easy to access or bootable. The Terminal commands are easy to find through google.

Download Espérance DV. I made a 2GB disk and put my firefox cache and my most-used apps onto it.

[iamcheerful]

i would love to make it bootable ;)
any workaround or special tips to bring back the good old days of RAM disk? i know it is volatile memory but i'm fine with it as long as it doesn't burn a hole in the pocket. SSD is still a bit too rich for my taste at the moment.

that said, any idea if in realworld test that SSDs will be outperformed by RAM/RAM Disk?

*on paper, definitely RAM is way faster than SSD.

*well, depends on what kind of RAM too i guess. ;)

p.s. Thanks for the recommendation of Espérance DV. The one I used to use --- ramBunctious. i used to use their Peek-a-Boo software in OS 9 too. Was very useful for me.

[Tesselator]

Before we try I think a RAM-Disk is nearly the speed of RAM. On a 2006 mac Pro 1,1 that's 1.7 to 1.8 gigabytes per second. An SSD is only 2 or 3 times faster than a single drive - or about the same speed as a 2 or 3 drive RAID 0 with drives that have the new 500GB platter densities.

Here's a RAM Drive for anyone to try: http://www.macupdate.com/info.php/id/16518

Or build one by hand in the CLI. Or with the included script at: http://osxdaily.com/2007/03/23/create-a-ram-disk-in-mac-os-x/

Here's what I get on a MacPro 1,1 on my brand new and otherwise free 2GB RamDrive:


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Compare with the tests performed on a 3-drive RAID0 here: http://forums.macrumors.com/showpost.php?p=7673878&postcount=1


http://tesselator.gpmod.com/Images/_Equipment_n_Tutorials/_RamDrive_Tests/QuickBench_RamDrive_001.jpg

http://tesselator.gpmod.com/Images/_Equipment_n_Tutorials/_RamDrive_Tests/QuickBench_RamDrive_002.jpg

http://tesselator.gpmod.com/Images/_Equipment_n_Tutorials/_RamDrive_Tests/QuickBench_RamDrive_003.jpg

http://tesselator.gpmod.com/Images/_Equipment_n_Tutorials/_RamDrive_Tests/ZoneBench_RamDrive_001.jpg



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Compare with the previous tests performed on a 3-drive RAID0 and one SSD here: here (http://forums.macrumors.com/showpost.php?p=7829635&postcount=31) and here. (http://forums.macrumors.com/showpost.php?p=7829393&postcount=30)


+--------------------------------------------------------------------------------------+
| Blocksize | IOPs | Throughput | User CPU | Avg Latency | Max Latency |
+---------------------+----------+--------------+----------+-------------+-------------+
512 Seq Read 417290.7 203.755 MB/s 1.610 s 0.009 ms 12.976 ms
Random Read 271817.7 132.723 MB/s 3.108 s 0.014 ms 0.564 ms
Seq Write 358143.7 174.875 MB/s 1.687 s 0.010 ms 10.620 ms
Random Write 15887.9 7.758 MB/s 4.670 s 0.250 ms 1.126 ms
Create scratch file 369480.0 180.410 MB/s 1.712 s 0.010 ms 32.342 ms
1 K Seq Read 437331.2 427.081 MB/s 0.797 s 0.009 ms 0.050 ms
Random Read 285235.8 278.551 MB/s 1.451 s 0.013 ms 0.062 ms
Seq Write 312146.3 304.830 MB/s 0.865 s 0.012 ms 11.457 ms
Random Write 16240.3 15.860 MB/s 2.288 s 0.245 ms 0.998 ms
Create scratch file 288312.6 281.555 MB/s 0.820 s 0.012 ms 32.177 ms
2 K Seq Read 410844.9 802.431 MB/s 0.427 s 0.009 ms 0.057 ms
Random Read 280509.5 547.870 MB/s 0.736 s 0.014 ms 0.069 ms
Seq Write 220705.1 431.065 MB/s 0.482 s 0.016 ms 27.525 ms
Random Write 16215.8 31.671 MB/s 1.138 s 0.245 ms 0.923 ms
Create scratch file 193014.5 376.982 MB/s 0.465 s 0.018 ms 27.067 ms
4 K Seq Read 349756.6 1366.237 MB/s 0.229 s 0.011 ms 0.075 ms
Random Read 261645.0 1022.051 MB/s 0.370 s 0.015 ms 0.085 ms
Seq Write 124963.4 488.138 MB/s 0.260 s 0.026 ms 23.686 ms
Random Write 30259.0 118.199 MB/s 0.447 s 0.131 ms 3.020 ms
Create scratch file 105937.2 413.817 MB/s 0.262 s 0.032 ms 27.385 ms
8 K Seq Read 257636.0 2012.781 MB/s 0.128 s 0.015 ms 0.092 ms
Random Read 213058.1 1664.517 MB/s 0.202 s 0.018 ms 0.062 ms
Seq Write 68902.9 538.304 MB/s 0.129 s 0.046 ms 24.968 ms
Random Write 26680.4 208.441 MB/s 0.230 s 0.147 ms 2.949 ms
Create scratch file 72522.3 566.580 MB/s 0.142 s 0.045 ms 23.822 ms
16 K Seq Read 164677.9 2573.092 MB/s 0.068 s 0.023 ms 0.050 ms
Random Read 145740.2 2277.191 MB/s 0.111 s 0.026 ms 0.081 ms
Seq Write 19418.9 303.421 MB/s 0.099 s 0.204 ms 0.342 ms
Random Write 18928.5 295.757 MB/s 0.166 s 0.209 ms 0.341 ms
Create scratch file 28098.5 439.039 MB/s 0.068 s 0.108 ms 34.850 ms
32 K Seq Read 91480.8 2858.776 MB/s 0.038 s 0.041 ms 0.081 ms
Random Read 87383.9 2730.748 MB/s 0.056 s 0.043 ms 0.093 ms
Seq Write 15688.2 490.256 MB/s 0.046 s 0.251 ms 0.390 ms
Random Write 15317.5 478.672 MB/s 0.071 s 0.257 ms 0.377 ms
Create scratch file 14507.0 453.345 MB/s 0.036 s 0.214 ms 35.633 ms
64 K Seq Read 48855.0 3053.435 MB/s -0.116 s 0.076 ms 0.199 ms
Random Read 44572.9 2785.806 MB/s 0.029 s 0.079 ms 0.198 ms
Seq Write 10332.5 645.781 MB/s 0.025 s 0.382 ms 0.666 ms
Random Write 10048.9 628.057 MB/s 0.037 s 0.392 ms 0.521 ms
Create scratch file 7025.9 439.116 MB/s 0.020 s 0.439 ms 36.258 ms
128 K Seq Read 24754.4 3094.299 MB/s 0.010 s 0.144 ms 0.354 ms
Random Read 25561.1 3195.143 MB/s 0.016 s 0.137 ms 0.367 ms
Seq Write 6153.2 769.149 MB/s 0.012 s 0.640 ms 1.104 ms
Random Write 6042.6 755.330 MB/s 0.016 s 0.651 ms 0.997 ms
Create scratch file 4137.7 517.207 MB/s 0.013 s 0.836 ms 30.693 ms
256 K Seq Read 12862.8 3215.693 MB/s 0.006 s 0.284 ms 0.567 ms
Random Read 13205.7 3301.420 MB/s 0.008 s 0.283 ms 0.520 ms
Seq Write 3167.5 791.868 MB/s 0.007 s 1.245 ms 3.135 ms
Random Write 3012.2 753.062 MB/s 0.012 s 1.308 ms 1.794 ms
Create scratch file 2042.0 510.500 MB/s 0.007 s 1.584 ms 40.829 ms
512 K Seq Read 6396.2 3198.081 MB/s 0.003 s 0.570 ms 1.052 ms
Random Read 6883.5 3441.748 MB/s 0.006 s 0.538 ms 1.020 ms
Seq Write 1433.3 716.666 MB/s 0.004 s 2.741 ms 5.827 ms
Random Write 1285.8 642.885 MB/s 0.006 s 3.051 ms 3.615 ms
Create scratch file 970.1 485.045 MB/s 0.006 s 3.229 ms 38.185 ms
1 M Seq Read 2603.7 2603.743 MB/s 0.005 s 1.450 ms 2.281 ms
Random Read 2429.0 2428.953 MB/s 0.006 s 1.460 ms 2.993 ms
Seq Write 576.4 576.439 MB/s 0.003 s 6.745 ms 12.633 ms
Random Write 641.1 641.067 MB/s 0.004 s 6.055 ms 7.501 ms
Create scratch file 487.4 487.353 MB/s 0.009 s 6.619 ms 35.948 ms
+--------------------------------------------------------------------------------------+


Benchmark Parameters Summary
============================


Device : RamDisk (/dev/disk7), write Media
Block Size Range
Start: 0.50 K
End: 1 M
File I/O Size: 20 MB
Number of threads: 4
File System Cache: Off
Read Ahead: Off
IO type: File IO
Tests Run:
Sequential Read
Sequential Write
Random Read
Random Write




Results 906.19
System Info
Xbench Version 1.3
System Version 10.5.7 (9J61)
Physical RAM 12288 MB
Model MacPro1,1
Drive Type Apple read/write RAM-Drive
Disk Test 906.19
Sequential 553.47
Uncached Write 415.27 254.97 MB/sec [4K blocks]
Uncached Write 1242.03 702.74 MB/sec [256K blocks]
Uncached Read 282.08 82.55 MB/sec [4K blocks]
Uncached Read 2132.99 1072.02 MB/sec [256K blocks]
Random 2498.42
Uncached Write 1195.78 126.59 MB/sec [4K blocks]
Uncached Write 2303.16 737.33 MB/sec [256K blocks]
Uncached Read 8109.22 57.46 MB/sec [4K blocks]
Uncached Read 4825.48 895.40 MB/sec [256K blocks]
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I must say, I thought the results would have been much better than this! After all RAM by itself not formatted as a "device" clocks on this machine at 1.7 GB/s. Still it whomps an SSD and my 3-green-Drive RAID0.

Hmmm... Thoughts?

[iamcheerful]

http://techreport.com/articles.x/16255

Did a search, here's an article written early this year on SSDs and RAM Disk. Look thru' the next few pages for the benchmarks if interested.

updated:
>> Page 6 (http://techreport.com/articles.x/16255/6) on some interesting results. Reads and Writes ...
>> Page 11 (http://techreport.com/articles.x/16255/11) on power draw. SSD rules. RAM are apparently too eager to make the world less Green ...

[iamcheerful]

Any idea what's the life expectancy of RAM? Is there also a read write upper limit where errors will start exhibiting?

[Tesselator]

Any idea what's the life expectancy of RAM? Is there also a read write upper limit where errors will start exhibiting?

I dunno what either are but there are for both. I guess life expectancy for RAM is at least several times longer than it's interface. Meaning for example, that I still have sipps and dips (http://media.digikey.com/photos/NXP%20Semi%20Photos/568-8-DIP,SOT97-1.jpg) that work but there's no machine sold today that will use them nor would 4k chips be useful today. Right? It changes on us so fast:

http://www.meustutoriais.com.br/wp-content/uploads/2007/08/ram.jpg

[iamcheerful]

indeed.
it appears more easy to get a defective RAM than to get a RAM die of old age. :p

[VirtualRain]

Given that SSDs are all the rage these days, be it in portables or desktops, I just want to ask for the opinions of our mac community how do these 2 perform.

I'll likely do a simple perception test with my pb3400c/200 & 240 MHz vs the early 2008 Mac Pro (unfortunately, no SSD equipped yet)

It won't be a totally objective test, as far as possible I want to try to do a realworld kind of test. That said, I'll be disabling Flash or maybe even all plug-ins. However will retain Java & Java script settings.

I was kinda disappointed Apple didn't continue their RAM Disk trick with OS X (RAM is so cheap now, think of what we can do with a 16 GB Bootable RAM Disk!)

Still recall the days where I run my pb3400 on RAM. She was so quiet and can last at least 4.5 hrs on a single battery charge. Writing on such a machine is so nice as it is rather cool and no noise.

Here's why a RAM disk doesn't make any sense on OSX...

From a former Apple employee...

That thing is snake oil, as are the vast majority of ramdisk products on OS X. Designing a ramdisk that works well on OS X is remarkably difficult because backing a block device into wired memory causes the contents to be double buffered above it in the Unified Buffer Cache.

For transient data on systems with no VM pressure, what will happen is the file is created, the object backing it sits in the UBC, it might get synched to disk, but unless you are running low on ram it stays in ram as well. That is why you see no speed increases, all you are doing is eliminating the background asynch writeout, and you are wasting a lot of ram to do it. More importantly, if you are actually creating a wired ram disk you are eating a ton of kernel address space which can be an issue if you have a lot of memory (large page tables) or several video cards.

Source... http://www.ocztechnologyforum.com/forum/showthread.php?t=52845

[300D]

It works great for me.

[thepawn]

OS instituted RAM drives -should- always be as fast as the bus and filesystem implementing it will allow. SATA-interface based ram drives will run into the same interface limitations that the newest SSD drives are bumping into - SATA maximum throughput.

[iamcheerful]

VirtualRain, thanks for the info.

OS instituted RAM drives -should- always be as fast as the bus and filesystem implementing it will allow. SATA-interface based ram drives will run into the same interface limitations that the newest SSD drives are bumping into - SATA maximum throughput.

Yep, that I am well aware too. Any idea what was the limitation back then ... say for example the pb3400c? i.e. what was the interface the RAM was to the computer. (not sure if i worded it correctly, hopefully you get what i'm trying to ask)

with the latest Mac Pro (Early 2009 models) these should be able to have a really impressively high speed interface given the way the CPU and Memory interacts. i don't know if i'm right in saying this, if Apple con't the Booting of RAM disk technology, things really will fly and not at the appalling cost of SSDs (yes, prices has dropped significantly, but still RAM appears more affordable cause one can use it as normal RAM and also double as a boot ... yeah, it is volatile)

guess what would be good is the best of both worlds ;)

so SSDs and HDDs can co-exist happily too. :p

[thepawn]

Heh, and old school Powerbook 3400c had 40Hz/60ns memory. :)

[thepawn]

I still have sipps

You forgot ZIPP chips... I had a pile of them for my Amiga 3000. ;)

[iamcheerful]

hahaa!

40MHz 60ns ... wow that could compare (real-world benchmarks) with the TiPB G4 400MHz machine (this couldn't boot off the RAM Disk) I could still create a RAM Disk in OS 9 then but not boot off that.

Something about the new world rom and old world rom thingy ... i never really got into the nitty gritty; more of a user, thus i typically prefer real-world testing over synthetic ones.