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Poor mans SSD ;-)

Bloody awesome work you're doing here! And lots of updates to fill in the void made by the lack of rumors.

Hell, when USB3 comes out, you're gonna be ready and waiting aren't you:D RAM is going to be the bottle neck when that comes around.

Just one more thing: I thought that all USB transmission processing is done by the CPU, so is there much CPU overhead when hammering out a lot of IO over the software RAID? Just curious, unless the overhead is so small it's insignificant.

One more thing: 800 read/s! Now that is something that's nice to have when you start running out of RAM and hit the swap space.
 
I can't wait to get my corasir gt drives, and test that out. I think I will be able to hit the max, if I set up another 4 USB raid to write to.

Oh, what block size did you set your raid to?
 
I'm up and running. Seems pretty fast but I haven't had time to install applications yet. I'll try the AJA benchmark. Hadn't thought about that one :) I have to go out for a couple of hours, but I'll let you know...
 
sammich said:
Bloody awesome work you're doing here! And lots of updates to fill in the void made by the lack of rumors.

Hell, when USB3 comes out, you're gonna be ready and waiting aren't you:D RAM is going to be the bottle neck when that comes around.

Just one more thing: I thought that all USB transmission processing is done by the CPU, so is there much CPU overhead when hammering out a lot of IO over the software RAID? Just curious, unless the overhead is so small it's insignificant.

One more thing: 800 read/s! Now that is something that's nice to have when you start running out of RAM and hit the swap space.
Click to expand...

When I'm benchmarking I cant se any significant CPU usage at all. I was worried about that, but it doesn't seem to be a problem :)
 
Just a trailer...

:d
 

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WPB2 said:
I can't wait to get my corasir gt drives, and test that out. I think I will be able to hit the max, if I set up another 4 USB raid to write to.

Oh, what block size did you set your raid to?
Click to expand...

I set it to default 32kb. Haven't tried to play much with block sizes yet.

Don't be to disappointed if the Corsairs doesn't deliver 32 MB/s each. A-data promise 30 MB/s read pr stick but that seems hard to reach... Can't wait to hear about your findings though :) Good luck!
 
madmaxmedia said:
Thanks OP, this is great stuff!

I just saw this ad for 200x (up to 30MB/sec) 8GB stick for $23 with coupon. Not only that, they're advertised as being WATERPROOF! ;)

http://www.supermediastore.com/supe...1030ActiveA&emc=el&m=576069&l=43&v=63ee2ce6be

In a few months USB sticks will be even cheaper, making this even more practical.
Click to expand...

Yep, Moore's law rox! It's a pity that coders are wasting the power of computers today. I remember when Digital GEM was running smooth on a 4.77 mHz PC with 5 1/4" floppies, though I must admit it's features were rather limited...:D
 
There's allways a catch...

I'm testing like crazy with AJA's benchmark program. The one thing that bothers me is write performance on small (4k) blocks. They seem pretty slow. It's a good thing they're so small ;)

It doesn't seem to affect the system performance, but it's an early stage to say anything definitive. I also need to try different Block sizes for the raid.

It seems to be a general problem with SSD, but as you can see my 2 TB MyBook FW800 Raid0 has similar problems. Once we reach the large blocks the MyBook is seriously left behind! It's all in they eye of the beholder, read what do YOU need most?

But close to 80 MB/s with USB? What do you think? Anyone tried this with 16 sticks? :D
 

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EdbBob said:
I'm testing like crazy with AJA's benchmark program. The one thing that bothers me is write performance on small (4k) blocks. They seem pretty slow. It's a good thing they're so small ;)

It doesn't seem to affect the system performance, but it's an early stage to say anything definitive. I also need to try different Block sizes for the raid.

It seems to be a general problem with SSD, but as you can see my 2 TB MyBook FW800 Raid0 has similar problems. Once we reach the large blocks the MyBook is seriously left behind! It's all in they eye of the beholder, read what do YOU need most?

But close to 80 MB/s with USB? What do you think? Anyone tried this with 16 sticks? :D
Click to expand...

I decided not to get the Corsair's, and go with the A-data PD7's they aren't as fast as the 4GB Corsair's but they are faster than the 8GB corsairs, and have a very low seek time. I think it was right around 1ms.
 
Last night was a bit disappointing, but today I've studied some more and tested a bit.

Using AJA's benchmark I found that the Trust hubs i have slow things down a lot! After reading I came across hubs with something called Multi TT (Transaction Translators). I haven't yet figured it out, but it could be what I'm looking for.

Testing one stick and no hub gives read of 34.3 MB/s. Running the same stick through a hub gives 23.2 MB/s. With three other sticks connected to the hub it decreases to 12.9 MB/S :confused:

Two sticks in raid0 with no hub gives 53.6 MB/s, two stick raid0 via one hub gives 29.4 MB/s :( Four sticks in raid0 via one hub gives 37.5 MB/s... Two sticks in raid0 via the hub in my 23" ACD gives 42.6 MB/s!

Wow that's a lot of numbers :eek:

I'm not to scared about write wear to the sticks. I found people running Windows from CF cards with sata converters in raid0 for more than a year :) Btw. They also have problems with 4k blocks!

Went to my local hardware pusher, and he thinks he has a multi TT hub in a shipment that arrived today, and he offered me to borrow it for testing. (What a nice man!!!) It'll be unpacked tomorrow.

"If at first you don't succeed, try again. Then quit. No use being a damn fool about it." -- W.C. Fields
 
WPB2 said:
I can't wait to get my corasir gt drives, and test that out. I think I will be able to hit the max, if I set up another 4 USB raid to write to.

Oh, what block size did you set your raid to?
Click to expand...

I tried using different block sizes striping the raid0 with two sticks through the ACD hub and found that 16k raid blocks give slightly better perf. Especially writing small blocks. 50% faster write... 256k blocks slows it down considerably!

Hope this babel makes sence ;)
 
This is fascinating, but give the rather small size and increasing possibility of data loss with growing raid-0 arrays, what exactly would be the intended utility of this device/idea?

Scratch disk? OS partition? ??
 
pprior said:
This is fascinating, but give the rather small size and increasing possibility of data loss with growing raid-0 arrays, what exactly would be the intended utility of this device/idea?

Scratch disk? OS partition? ??
Click to expand...

Well, it started with curiosity, but after a bit of testing, I think (with the right setup) that it could become my system disk. I really like the flashraids extremely low acces time compared to HDD, and I always found raids interesting. Raids and multiprocessor computers is the way to go towards more speed ;)

I'm not scared of running large raid0 flashraids. They seem pretty solid, and if I get it working, I will use Time Machine for backup. :) Large raid0s with HDD is a pain. I remember having a 16 drive raid with Micropolis SCSI disks. The ones with metal dust in the center bearing. Now THAT was frustrating!!! (And it killed the factory...)

Most of all I want to find out more about SSD and this was an easy way, without taking my iMac apart.

Finally there's something fascinating about running a computer with only RAM. Haven't done that since my Commodore VIC20 :D (I gladly admit I'm a geek)
 
78 MB/s with only 4 sticks!

Keyboard hub in the usb port closest to the earphone plug. Then the ACD hub, and finally my mouse. Two sticks in keyboard (looks funny) and two in the ACD. Total of 32 GB. Raid0 (16K blocks):
 

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EdbBob said:
Keyboard hub in the usb port closest to the earphone plug. Then the ACD hub, and finally my mouse. Two sticks in keyboard (looks funny) and two in the ACD. Total of 32 GB. Raid0 (16K blocks):
Click to expand...

Still gotta get that write performance up.

You can now get a 128GB SSD on newegg for around 300.00. The best read speed I saw was 175 MB/sec, and write speed 100 MB/sec
 
Conclussion

Well...

The problem with this idea is two things:

1. Data clutter on the USB Busses.

2. Random write of small blocks.

The first problem could probably be solved with a good hub (Multi TT!).

The second problem is a lot harder to fix. After reading a lot about SSD, it seems to be a general problem of most SSD drives. The thing is that flash ram can't just write a small file.

"The drive itself cannot just update the sectors you are changing, but must merge your changes with existing data to update a complete erase block. As Flash SSDs have gotten faster and larger, erase blocks have grown as well. Flash erase blocks used to be 16K in length. Now they are 1 Megabyte for small SSDs extending up to as large as 4 Megabytes for some models."

This is at least a major problem with older and cheaper SSD. In the scary world of Windows one can purchase a software utillity called MFT (Managed Flash Technology). It's pretty expensive and has a horrible license system! This seems to work as an advanced cache layer, that function between the OS and the SSD. It thereby increase random writes a lot! Sorry, not available for Mac...

As far as I can read, Apple is working on implementing ZFS from Sun into SnowLeopard. This filesystem should be able to do something similar. That's an absolute must with SSDs and it could also be integrated into the SSD hardware. It seems Intel has done something like that with their new drives. Until it arrives on the Mac platform I would be cautious getting a SSD for your Mac. Access times are amazing. Far better than any HDD. But randomly writing small blocks is a pain. It severely slows down the system!

People all over the internet is complaining about SSD performance (even MBA owners). For now, I therefore conclude, that it's not worth the trouble continuing this experiment. When things develop I will pick it up. There's no doubt that A-data's sticks are very fast (with 128K blocks and above), and they are perfectly raid'able. I just hadn't figured out that SSD is in a very early stage, and that no one has a good solution, to some of it's problems (yet)...

Over, roger and out :D
 
awesome work, thanks for all the info. I will be getting my sticks tomorrow, and testing a few things myself. I will post results. This is becoming sort of a hobby. I think I'm turning into a geek.
 
WPB2 said:
awesome work, thanks for all the info. I will be getting my sticks tomorrow, and testing a few things myself. I will post results. This is becoming sort of a hobby. I think I'm turning into a geek.
Click to expand...

Good luck geeking! :) It is kind of a fascinating puzzle. I use an application called Poser a lot, and I tried to move it to a Raid of only two sticks. I found the performance boost quite satisfying :) It uses the disk a lot, but mostly for reading smaller files, and here the raid really shines. Test your sticks single first to have an idea of their performance. And try a single stick through your hub if you use any, to see how much the hub eats...

It's still an interesting project, with USB ram getting faster and cheaper every minute, and MFT and ZFS moving along.

Looking forward to hear about your results, but be careful! It can be quite frustrating at times. Then it's best to leave it and come back with new ideas later... And trust me. They will come ;)
 
PS It still amazes me that you can move applications on a Mac. Try doing that on a PC... :D I love my :apple:
 
I got some new hubs today. Deltaco. They are way better than the Trust ones I had. Connected 8 sticks, via hubs, directly to the Mac. That runs a lot better. 45 MB/s write speed and 70 MB/s read. It doesn't do any hickups, and seems to run much faster and steady. I'll give this one a chance and install Leopard.
 
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