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SATA RAID for HD
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RMN
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PostPosted: Wed 26 May 2004, 23:20    Post subject: SATA RAID for HD Reply with quote

If you're seeing this, you're in the right spot [note: this was originally in a private forum].

Current theories:

  1. Fully internal RAID
    Controller: Internal SATA RAID controller (or plain SATA controller + RAID software)
    Drives: SATA
    Cables: Nx SATA cables, all inside the case
    Other: Requires a server case

  2. External RAID with internal controller
    Controller: Internal SATA RAID controller (or plain SATA controller + RAID software)
    Drives: SATA
    Cables: Nx SATA cables, going from one case to the other
    Other: External array case, cooling

  3. External RAID with external controller
    Controller: External SATA RAID controller with SCSI host connection
    Drives: SATA
    Cables: Nx SATA (inside array case), 1x SCSI (between array and computer)
    Other: External array case, cooling, SCSI host adapter


Also worth considering: a SATA drive enclosure, with a backplane, instead of a custom box with cables.

Personally, I'm aiming for the first solution, with a Chieftec AR-2000 case, 10 WD 250 GB drives, a dual Opteron motherboard and two RAIDCore 8-port controllers (spanned array), but this depends on how quickly RAIDCore manages to release its new (fixed) model.

RMN
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mdc1138



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PostPosted: Thu 27 May 2004, 0:06    Post subject: Reply with quote

I'm presently inclined to go for option 2, since it is the least expensive.

Although in time I'm going to want Option 3, since it is more scalable.

External controller = higher cost!

I'm all about democratization of technology.

Medea offers arrays based on U320 interfaces with ATA drives, but their prices are pretty high - $5 to $7 per gig. Plus a few hundred for the interface card. Ouch! Granted, that is RAID 3, so you do have data stability that isn't present with a RAID 0, and that is a LARGE comfort. The bigger the RAID, the better the price per gig. A 2TB array costs $5 per gig.

And yes, if you need more storage it scales well (add several more units).

But to have the same datarate and the same capacity, I could do it for less than a a dollar a gig.

Want data security? OK, a high speed, FireWire based backup can be had for an additional $2300 or so. Big, cable ridden mess. Cases everywhere...but mor than $5000 less for the same drive performance and SOME kind of guranteed back.

YES, it's clumsy and sprawling and bigger.

YES, it's not as secure - you could lose a day's work.

But for less than half the price, I could risk it.
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RMN
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PostPosted: Thu 27 May 2004, 4:17    Post subject: Reply with quote

mdc1138 wrote:
I'm presently inclined to go for option 2, since it is the least expensive.


Actually, option 1 is the least expensive, but only if you can pick your case.

BTW, these guys are cheaper than Medéa, but still very expensive:

http://www.hugesystems.com/

If there was some way to buy just the controller (or the controller and the case, but with no drives), it could be interesting.

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mdc1138



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PostPosted: Thu 27 May 2004, 4:27    Post subject: comments on option 1 Reply with quote

option 1 is the least expensive on a PC...on a Mac, significant costs can occur to get internal RAID beyond 2 disks.

PC has a large advantage on cost of controllers, but I find FCP to be a really nice, interoperable editor. But I reallly like, and admire, the new workflow advantages of the new AE 6.5 and Premiere Pro copy/paste workflow - it's about time.

-mike
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PostPosted: Thu 27 May 2004, 15:48    Post subject: Reply with quote

Premiere Pro is one of the buggiest pieces of software I've ever used. And it's taking them one year just to fix the bugs that should never have made it through QA in the first place. And now they're going to (try to) charge their clients money for the "upgrade" that is acually just a bug fix.

The good thing about Premiere is it can load files in a ton of different formats, it can understand different alpha channel mattes, and it has a lot of compositing modes. So it's great when you need to mix files coming from several different sources. But, for editing, FCP is defintely better than Premiere Pro, at this stage. Still far from perfect, but definitely better. I wish Discreet would make an editing program (based on 3DS MAX's philosophy, not Combustion's)...

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RMN
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PostPosted: Thu 27 May 2004, 15:51    Post subject: Reply with quote

Quote:
>> I. In fact, I can build a 2TB array for $1909 Smile.
>> The problem is performance and reliability. I
>> want at least 300 MB/s and I don't want to
>> have to reboot the computer 3 or 4 times because
>> it suddenly decided that a drive was "offline"
>> when it wasn't.

> OK, well then like I said, please tell me (itemized)
> how you can build a cheap 2TB array. If it looks
> better than SATA, I'll drop SATA.


It *is* SATA. That's precisely the problem. Most SATA RAID controllers have some dramatic problem (missing drives, corruption at bus speeds above 66 MHz, very high CPU utilisation, etc.). The alternatives are to use non-RAID controllers, and RAID them in software (works, is fast, but will fill all my PCI slots) or going for SCSI (controller is cheaper, but the drives are much more expensive).

For _my_ situation, I'm just waiting for RAIDCore to release their fixed RAID controller (that doesn't have the "offline drive" problem).

For your situation, I think you should be looking for external SATA-to-SCSI or SATA-to-FC RAID controllers (i.e., that connect to SATA drives, but can use an external SCSI cable to connect to the computer). They do exist, the problem is finding someone that will sell you just the controller, without forcing you to buy the drives from them (at 3x the price).

If the controllers themselves turn out to be ridiculously expensive, then it's back to the 8-SATA-cables-hanging-out-of-the-case method. But if their cost is just slightly higher than the internal controllers, I think it's definitely worth it, to have a tidy, easy to connect solution.

In fact, I'm currently trying to get in touch with a couple of Taiwanese companies that make standa-lone SATA RAID controllers. If I manage to find out anything about them (namely price and performance), I'll let you know. So far the most promising one is one called 'Areca', but they don't seem to have any distributor in Europe / the USA, and I can't find any mention of them in any website (apart from their own).

Quote:
>> And they'll never buy an array that
>> isn't certified by the people making
>> the card. It's the Avid mentality.
>> If it doesn't have the logo, it doesn't exist.

> I know there are people like you're talking
> about out there. I'm not trying to make money off
> of this.


But you're talking about "getting the manufacturers interested in your design". The only way the manufacturers are going to get interested is if they see a chance of making a profit.

Quote:
> I personally believe they'd start taking notice
> when they see people editing HD on systems that
> cost 10% of what they paid,


They'll assume those systems are 90% worse. I've been through this 8 years ago, with DV / Beta.

Quote:
> Tell me how you can build a 2TB array for 1909.


8 x WD SATA 250 GB drives ($193 each)
1 x RAIDCore 4852 controller ($365)

There are cheaper controllers, but RAIDCore has by far the best array management software.

RMN
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deproduction



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PostPosted: Thu 27 May 2004, 17:20    Post subject: Tell me something I don't know Reply with quote

I thought you were going to tell me how to build a DIFFERENT 2TB raid for under $2K. If the only problem with the external SATA model is messy and unshielded cables, that problem will be solved. I'm not here to argue about whether or not manufacturers will get involved. I think it is a given... We start building 2TB RAIDS for under $2K and editing HD on a sub-$10K system, but complaining about our cables sucking, and some manufacturer will take $40 worth of SATA cables and make them work for our needs and sell them back to us for $150.
Right now, nobody has been able to come up with an HD-capable RAID for under $5K, and this is a solution for as little as $2K.

Did you ever answer whether or not you thought 9 drives would work for HD? 10 is the most we can do with just one PCI card. I'd rather not use an external boot drive, but it sounds like you think we need 10 drives for functional HD editing, so we'd have to use both internal and the 8-port PCIX drive.
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RMN
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PostPosted: Thu 27 May 2004, 17:36    Post subject: Re: Tell me something I don't know Reply with quote

As I said, I doubt you'll find any manufacturer interested in that solution, due to the very small potential market (the manufacturers are in it for the money, not philanthropy). Doesn't hurt to try, though. But first you need to make sure the controller can actually support the speed you need.

deproduction wrote:
Did you ever answer whether or not you thought 9 drives would work for HD? 10 is the most we can do with just one PCI card. I'd rather not use an external boot drive, but it sounds like you think we need 10 drives for functional HD editing, so we'd have to use both internal and the 8-port PCIX drive.


So you're planning to use software RAID? A hardware RAID controller will not be able to use drives that are not connected to it. So if your controller is 8-port, the maximum you can use is 8 drives.

8 (or 9) drives should be fine for YUV 4:2:2 HD. For RGB (4:4:4) or RGBA (4:4:4:4), I doubt it (unless you short-stroke the array to less than 50% capacity).

This, based on the speed of the drives, and assuming a "perfect" controller. The problem is, many controllers actually hit a ceiling after a certain number of drives. If the controller's chip really cannot go past 150 MB/s, for example, adding more drives isn't going to make any difference.

Count on these values:
  • 7200 RPM drive speed: 50 MB/s (outer sectors) to 30 MB/s (sustained)
  • Array speed (in RAID-0): Number of drives multiplied by sustained speed
  • Required speed for uncompressed 1080 @ 30 fps / YUV 4:2:2: 170 MB/s (requires 6 drives, in a "perfect" situation)
  • Required speed for uncompressed 1080 @ 30 fps / RGB 4:4:4: 280 MB/s (requires 10 drives in a "perfect" situation)
  • Required speed for uncompressed 1080 @ 30 fps / RGBA 4:4:4:4: 350 MB/s (requires 12 drives in a "perfect" situation)

The values include audio and a small safety margin. I confirmed the first two values with a few HD card manufacturers (some are saying 160 MB/s for YUV 4:2:2 but I think it's too tight).

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PostPosted: Thu 27 May 2004, 17:38    Post subject: Reply with quote

Quote:
> Obviously, if you are talking more than 4
> ports, some would have to be external.


For Macs, yes (assuming no-one makes 3rd party server cases).

Quote:
> Then there's the data cable issues. I'm told that
> external boxes should be used with external SATA cables,
> which have more shielding than internal cables. However,
> when I used the stiffer external cables, I broke the SATA
> connectors on both a drive and a controller. Grrr.


The problem is, there aren't external SATA cables. What some companies are selling as "external" cables are just that: internal cables with more shielding. Western Digital makes proprietary connectors called "SecureConnect" that are more resistant, but they only work with WD drives, are only 50cm long, and don't do anything for the end of the connector that plugs into the controller. They'e meant to be used internally, anyway.

http://www.wdc.com/en/products/wdsc50rcw.asp

Quote:
> Having 4 to 8 SATA cables snaking out the back of the
> G5 may sound less than desirable visually but that's
> really the only way an external SATA box can work


The alternative is #3 in my message at the beginning of the thread. But only if you manage to find someone selling just the controller, because Medéa, Huge systems, etc., all charge ridiculous prices for the drives.

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mdc1138



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PostPosted: Fri 28 May 2004, 2:27    Post subject: Reply with quote

A few little tidbits I want to throw into the equation, Robert Morgan has covered these in his site:

1.) The Hitachi 7K250 and 7K400 drives run around 60 MB/sec at the edge, about 30 at the hub. So can bump the numbers up slightly.

2.) The Western Digital Raptor drives are even faster - 72 MB/sec at the edge, about 52-55 at the hub. And they hold something close to 65-70 MB/sec for about 70% of the drive. I have some hard numbers somewhere I can dig out, I made 4 and 6 drive arrays and diced into 10 partitions and speed checked them multiple times and derived averages to come up with the above numbers, which I'm vaguely recalling so I might be a little off. However, these are only 74GB drives, so poot on them.

3.) In a perfect situation you'd use all of the drives. OK. But in our non-perfect situation, you'd use maybe 40-70% of the drive, depending on the speed you needed for your particular application. The remaining part of the array? Feel free to use it for graphics storage, rendered AE files to be imported, DVCPRO HD or other offline/nearline codec footage, etc.

4.) Medea systems are more than just the box - they have a patented system wherein they do what I'd call counter striping - they call it zone something or other - where every other drive writes from the hub towards the edge of the platter (opposite of normal). This keeps the throughput of the system closer to an average no matter how full the array is. Smart. Patented and pricey, but still smart.

5.) Even with just PCI cards (2 of them) in a G5, with 2 internal drives, I've made a 6 drive array that DeckLink's tool reported at 390-405 MB/sec (excuse me, repeating myself). Doing a little math, that implies about 90% efficiency in a 6 drive setup (395/(72*6)=91.blahblah%). That's pretty good. And clearly, each card is pumping about 130 MB/sec if the load is equitably divided. If a 4 port card topped out at 150 MB/sec, that would be bad for our purposes. But each bus is supposed to be able to do 150 all by itself. And on a PCI-X bus, with the honkin' fast bus on the G5, this oughta work.

6.) Your data rate numbers strike me as a weensie bit high. Most of the Mac stuff is using the BlackMagic codec, and according to the BlackMagic Design website, the datarate for 1920x1080 10-bit 30fps is 136.72 MB/sec. Add in 20% for overhead (generous) and that's 163.2. If you only want 8-bit, it's about 150 MB/sec. OK, my numbers are pretty close to yours. Never mind. Just depends on how much safety margin you want.

7.) At the moment, I have a 4x160 GB Barracuda array set up. Not at all what I'd pick I were spending money, but it was what was available to me. Ran the disk tester gadget, it reported something like 206 MB/sec....which fits your 50 MB/sec numbers exactly. But better drives are available.

I plan on dicing up the drive with SoftRAID and testing every 10% to see what the falloff is, and then the final 10GB just to know what the tail of the drive can do, worst case scenario.

8.) By the way - using SoftRAID, messing with the block size settings DOES make a difference. I'll have to go back into my notes to see how much, and which is best, but it matters. Journalled on or off makes a difference too - no journalling is faster...but a LOT less safe in case of a crash.

Not meaning to quibble with RMN's stats, just wanted to voice my thoughts on the matter.

-mike
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mdc1138



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PostPosted: Fri 28 May 2004, 2:30    Post subject: Reply with quote

One more thing - I noticed that, inside the PPA, Inc. SATA boxes, there are these nice little one piece connectors that are power and SATA connector in one piece that plugs as a single unit into the drive. Who makes that, and can we get some more? RMN, you seem pretty good at parts scrounging and identifying, any clues? PPA, Inc. boxes are available at Fry's and come with shielded SATA cables. But sucky, rattling, crummy fans.
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RMN
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PostPosted: Fri 28 May 2004, 3:46    Post subject: Reply with quote

mdc1138 wrote:

1.) The Hitachi 7K250 and 7K400 drives run around 60 MB/sec at the edge, about 30 at the hub. So can bump the numbers up slightly.


What really matters is the sustained transfer rate (in other words, the speed in the inner sectors). Which is around 30 MB/s, as I mentioned above. Of course, you can short-stroke the drives to half capacity, and get a sustained (minimum) transfer rate closer to 45 MB/s, but I don't think it's worth it; it's simpler to just add more drives (if you're editing in HD, you need all the space you can get).

mdc1138 wrote:

2.) The Western Digital Raptor drives are even faster - 72 MB/sec at the edge, about 52-55 at the hub.



Yes, but they cost almost the same as SCSI drives (15% less), are hotter, and are limited to 74 GB.

mdc1138 wrote:

3.) In a perfect situation you'd use all of the drives. OK. But in our non-perfect situation, you'd use maybe 40-70% of the drive, depending on the speed you needed for your particular application. The remaining part of the array? Feel free to use it for graphics storage, rendered AE files to be imported, DVCPRO HD or other offline/nearline codec footage, etc.


You can't control where the OS puts each file. The only way to ensure that the HD video files are placed in the outer sectors of the drive is to create two partitions in each drive, and use only the first. Not all RAID controllers let you do this. With some, if you decide to use only the first 50% of the drive for your array, the remaining 50% will be inaccessible, so basically you're paying twice the price per GB. Make sure your controller (or software) supports doing this.

mdc1138 wrote:

4.) Medea systems are more than just the box - they have a patented system wherein they do what I'd call counter striping - they call it zone something or other - where every other drive writes from the hub towards the edge of the platter (opposite of normal). This keeps the throughput of the system closer to an average no matter how full the array is. Smart. Patented and pricey, but still smart.


I've heard that, but if that's the way it works, it's not smart, it's terribly stupid. An array's speed is determined by its slowest drive. If 4 drives are writing on the outer sectors (and take only 1 "time unit" to write 1 byte) and the other 4 drives are writing to the inner sectors, where it takes 2 "time units" to write one byte, then the controller can only send the next group of bytes after 2 time units. In other words, the array behaves as if all drives were writing to their slowest sectors.

mdc1138 wrote:

If a 4 port card topped out at 150 MB/sec, that would be bad for our purposes. But each bus is supposed to be able to do 150 all by itself.


The problem isn't the SATA speed, the problem is the speed of the RAID chip. For example, 3Ware's Escalade 8000 series maxes out at 190 MB/s, because their RAID chip can't process data faster.


mdc1138 wrote:

6.) Your data rate numbers strike me as a weensie bit high. Most of the Mac stuff is using the BlackMagic codec, and according to the BlackMagic Design website, the datarate for 1920x1080 10-bit 30fps is 136.72 MB/sec.


It's simple maths:

1920x1080 = 2073600 pixels per frame
10 bits per channel @ 4:2:2 = 40 bits per each 2 pixels = 20 bits per pixel
2073600 x 20 bits per pixel = 41472000 bits per frame
41472000 bits = 5184000 bytes
5184000 bytes x 30 fps = 155520000 bytes per second
155520000 B/s = 148 MB/s

And that's just video. Of course, if you use a compressed format, the size will depend on your compression level. For uncompressed, 10 bpc, 4:2:2 sampling, 30 fps, 1920x1080, you need 148 MB/s.

mdc1138 wrote:

Ran the disk tester gadget, it reported something like 206 MB/sec...


Reads or writes? And what RAID level?

mdc1138 wrote:

I plan on dicing up the drive with SoftRAID and testing every 10% to see what the falloff is, and then the final 10GB just to know what the tail of the drive can do, worst case scenario.


Is there something similar to WinBench for Macs? It gives you the speed across the whole drive / array. Here's an example (at the bottom of the page):

http://www.storagereview.com/articles/200401/20040126WD740GD_2.html

mdc1138 wrote:
I noticed that, inside the PPA, Inc. SATA boxes, there are these nice little one piece connectors that are power and SATA connector in one piece that plugs as a single unit into the drive. Who makes that, and can we get some more? RMN, you seem pretty good at parts scrounging and identifying, any clues?


Does it look like this? Or is it just a power + data connector on the end of a cable?

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mdc1138



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PostPosted: Fri 28 May 2004, 13:36    Post subject: Reply with quote

I'm going to respond to each in order:

1.) adding more drives can be tough on the mac, since at the moment, there is only one card out there that lets you add 2 more drives to the two internals we can already do. I was about to say you can only add one of the cards, but I realized that if the HD card goes in slot 4, then slots 2 & 3 can both have Seritek 1S2 cards. The only hindrance is that you'd have to remove the PCI slot cover from the card, drill/file/cut out holes to make room for the SATA cables to route through the holes to make to get them outside the box - the 1S2's ports are internal. The catch then would be whether the shared 100 MHz bus of slots 2 & 3 would be fast enough for the 4 drives. (Slot one is the AGP slot for graphics card).

6 drives is the max in this configuration, and at that point, you have to boot off of a FireWire 400 or 800 drive. FireWire 800 makes more sense - faster and leaves your FireWire 400 ports available for DVCPRO HD deck input, AJA I/O board, or other gadgetry. Ideally, I'd like to leave a SATA drive free for use as a boot drive - faster and more reliable booting, and one less damn external case.

Anybody have any comments/experience with 5 drive RAID zero? Is this not recommendable? I've always heard use an even # of drives for RAID zero.

2.) Those Raptor drives cost $205 each at zipzoomfly.com. The Cheetah 15K3 drives (same size) cost $550. But both are still tiny.

3.) Can't control where the OS puts the file, but it generally puts it in the next available empty space. Since on the Mac I'm using SoftRAID, I can partition. And then I can still use the rest of the drive space for non-HD throughput critical storage. That's what I meant before about using nearline codec, etc. stuff.

4.) Medea - that zone striping stuff - it's not too stupid, because instead of having a drive be twice as fast at start as it is at finish, and therefore making some of the drive be not fast enough, it lets the WHOLE drive array be fast enough...even though it isn't as fast as it COULD have been at the start. Anyway, my point is that Medea arrays are more than just the controller/box - I don't know if you can format the drives "their" way if it were any empty box, and I betcha they have to support particular drive models to do their stuff. Dunno, just conjecture.

5.) RAID chip speed - 2 answers:

a.) Ahh, good to know.
b.) RAID chip speed? What word RAID chip you speak of, white man? Me come from distant primitive lands of Mac, we hear of no RAID chip you speak of where I come from. We only know software RAID zero for SATA.

; p

6.) Woops, one should always qualify one's answers. Those 4xBarracuda #s came from intech's QuickBench. In more detail:
20 MB transfer size = 207 MB/sec reads, 216 MB/sec writes
100 MB transfer size = 208 reads, 224 writes

software RAID zero, SoftRAID 3.0.2, HFS+ Journalled, Workstation (128 Kb block size) setting

to answer your question about connectors, the connector itself looked like Conn1 in your link.

This is fun!

We are definitely going to get to the bottom of all this.

-mike
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mdc1138



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PostPosted: Fri 28 May 2004, 19:04    Post subject: Further update on Mac additional drives difficulty Reply with quote

So I just now gave up trying to get a DeckLink HD card into slot 4 on my G5, even though they have a support link specifically on how this is supposed to work...but it categorically doesn't on my box. I don't know if I have a wonkus/early G5 or DeckLink, but that sumbitch will NOT fit in there, it intersects substantially with a connector on the motherboard.

This one little difficulty is keeping me from installing a 2nd Seritek card to allow me to have a 6 drive array.

Shit shit shit shit shit!

-mike
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PostPosted: Fri 28 May 2004, 21:11    Post subject: Reply with quote

mdc1138 wrote:
The catch then would be whether the shared 100 MHz bus of slots 2 & 3 would be fast enough for the 4 drives.


A 100 MHz PCI-X bus has a theoretical limit of about 750 MB/s. The practical limit will be around 580 MB/s, which should still be more than enough (4 drives won't even reach 250 MB/s, and won't sustain more than 150 MB/s).

Quote:
Anybody have any comments/experience with 5 drive RAID zero? Is this not recommendable? I've always heard use an even # of drives for RAID zero.


Shouldn't make any difference. I'm pretty sure some of my SCSI RAIDs had 5 and 3 drives at one time or another.

Quote:
Those Raptor drives cost $205 each at zipzoomfly.com. The Cheetah 15K3 drives (same size) cost $550.


I was comparing them to 10K RPM models (ex., Fujitsu 73 GB costs around $245).

Quote:
Can't control where the OS puts the file, but it generally puts it in the next available empty space.


Generally, but you can't be 100% sure. This isn't something you want to find out during capture or export.

Quote:
that zone striping stuff - it's not too stupid, because instead of having a drive be twice as fast at start as it is at finish, and therefore making some of the drive be not fast enough, it lets the WHOLE drive array be fast enough...


Nope, sorry, if they are indeed set up as you described, then the speed of the array will be exaclty the same as the speed of a similar array, formatted normally, at the last sector. In other words, instead of an array that starts at 250 MB/s and ends at 150 MB/s, you have an array that always transfers at 150 MB/s. There's absolutely no advantage.

They might be doing some trick to improve the overall speed, but it's probably more complicated than formatting some drives backwards.

Quote:
RAID chip speed? What word RAID chip you speak of, white man? Me come from distant primitive lands of Mac, we hear of no RAID chip you speak of where I come from. We only know software RAID zero for SATA.


In land beyond mountain, where strange man no paint face with the dropping of the dodo, there lives RAID chip on card.

Keeps the load off the CPU, which is nice in database servers, and also when rendering real-time effects on video. Since you won't be getting many RT effects in HD anyway, I guess it's not a big problem if you lose 10% of the CPU cycles or so to handle the striping.

However, even when the card does not have a RAID chip, it still has a chip that bundles all the data coming from the SATA chips and sends everything through PCI. If the card is PCI-X, the chip will hopefully be pretty fast.

Quote:
20 MB transfer size = 207 MB/sec reads, 216 MB/sec writes
100 MB transfer size = 208 reads, 224 writes


Hm... that's weird. Most drives read faster than they write. Of course, caching works better for writes than reads, especially if the drive has some fragmentation.

Quote:
to answer your question about connectors, the connector itself looked like Conn1 in your link.


That's the same connector (backplane unit), just both sides.

RMN
~~~
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