What's faster? Built in hard drive or Promise Pegasus R4 4TB (4x1TB) RAID System connected with Thunderbolt?

Famous_Boi69 wrote:

For encoding video etc.

1TB 7200-rpm Serial ATA 3Gb/s hard drive

vs.

http://store.apple.com/us/product/H5184VC/A/Thunderbolt

And what about Thunderbolt drive vs. Solid State?

As Thunderbolt expands the internal Data-Bus to extern there should be (theoretically) no major speed difference in data transfer rate between the internal drive and a TB connected one.

http://en.wikipedia.org/wiki/Thunderbolt_%28interface%29

SSD is indeed faster than a conventional disk as there is no need to move parts for accessing data and therefore the SSD drive can use (theoretically) the full bus rate of the system for data transfer.

A raid, depending on used raid level and interface could be remarable faster as a single drive. http://en.wikipedia.org/wiki/Raid_levels

Lupunus

It is of no use until you add a PCI Express controller.

PCI Express 3.0 is not out yet but will be important.

Barefeats.... anyone not looking there first, should. Has done some tests.

USB3 Highpoint, another thing to consider.

SATA 3 with 6Gb is already proven mature interface for controllers and hard drives.

TB will improve in price, lower, and products, now that Intel will be rolling it out to everyone.

There are 8x PCI Express cards today to drive RAID5/6, from $400 and up generally.

http://www.macsales.com/

PCI Express Controllers:

http://eshop.macsales.com/Search/Search.cfm?Ntk=Primary&Ns=P_Popularity|1&Ne=5000&N=6943&Ntt=pci+express

"A chain is as strong as its weakest link."

Take a fast Hard drive. at the moment, about the fastest it can transfer data off the platters and send it to you AFTER it has located the correct track and the data are directly under the heads is about 125 MegaBytes/sec. THAT is the bottleneck.

A faster SATA transfer bus, a Thunderbolt Bus, USB3 Bus -- none are more limiting that the latency built into the drive itself. They do not make any real-world difference, until we start to talk about multiple drives with I/O overlap, such as a RAID, or SSD devices with shorter latencies.

ACK

The high bandwidth does help when you move data off an array over a single cable.

Cases with the older Port Multiplier were capable of 250MB/sec (actual, 300MB/s was spec) was useful and came out when drives were 75MB/sec and you could use 3-5 drives over one channel. Just like you use to with SCSI Ultra160 or Ultra320 controllers.

SATA 6G (550MB/sec) takes it up a notch.

As I said, Barefeats did some tests of RAID using USB3, SATA3, and TB (maybe SAS SCSI also).

You can get 700MB/sec off any well designed RAID controller array.

A single SSD today on 6G interface is interesting.

There are SSD PCIe controllers with embedded SSD style with 1GB/sec and 10-20Gb/sec (much like TB). But those speeds are going to need computers with PCI Express 3.0 for all the bandwidth hungry graphics, storage, and other I/O.

Your Mac Pro with 4 x SATA ports do not get 300MBsec independent bandwidth for each, no, they share a common controller, that is less than even 1Gb, more like 750MB/s and LIMITED to max of 275MB/sec over a single SATA port. About what SSD use to offer and less than new gen of SSD.

Famous_Boi69 wrote:

- (?) RAID Cards will speed up the performance of the HDDs (?)

To be correct: The speed of the HDD's did not speed up.

A Raid System enables the system to write or read at the same time in different HDD's what broadens the throughput of data.

That depends on the controller and the Raid-Level. (see http://en.wikipedia.org/wiki/RAID )

Normally you will choose a combination of Raid Levels e.g to create Failure-resistant disk systems, Failure-tolerant disk systems or Disaster-tolerant disk systems.

Lupunus

Striping gets its main speedup by overlapped I/O. Transferring data from one drive, while the other drive is doing a 12 msec seek, which would normally be "dead" time.

IF everything could line up absolutely perfectly, you could sometimes momentarily double the data transfer speed for two drives, triple it for three. But a lot of that is wishful thinking.

Executive summary:

Is striped RAID faster? yes

Is it four times faster for four drives? probably not

What else mucks it up? Anything that moves the heads to another area of the drive. Make sure you have a separate Boot drive, and best performance is when you have separate source and destination drives as well.

If the above is true, does this sound like a good setup?

• 4 x 1TB 7200-rpm Serial ATA 3Gb/s hard drive **all internal HDDs
• Mac Pro RAID Card

I think I'd be using RAID 0+1.

I'm thinking you'll be happier with something like:

• 4X 3TB (or 2TB) Hitachi 7200 SATA III 6GB/s hard drives (in the internal slots)

• Third party SATA III RAID controller

• SATA II (or SSD) Boot drive in the second optical drive slot

Use RAID 5.

With twice the SATA interface speed, it should run nicely...

Apple RAID card is close to being junk. It does not support more bandwidth, does not support 3TB drives, is only useful for RAID5 or SAS drives.

Famous_Boi69 wrote:

But with striping there is a performance increase, correct?

WARNING

Yes, with striping you have a performance increase but only:

If your setup is well organized.

WARNING

Only striping will kill ALL your data if one disk is damaged as a stripeset without an additional security set is not recoverable.

Additional, the increase of a stripset is not so big as one thought in times where hard drives are fast and the internal Bus is even faster.

If you want to use a (hardware) Raid you should also know, that this have a loss in capacity for your storage.

For instance a Raid 5 (Block-level striping with distributed parity).

The usable capacity can be calculated as: (Number of drives - 1) × (capacity of the smallest drive).

Example for 4 hard drives 500 GB each: (4 - 1) × (500 GB) = 1500 GB user data and 500 GB parity data.

I suggest you strongly to read the whole article there and also the articles behind the links at the end of the page BEFORE you make your decision: http://en.wikipedia.org/wiki/RAID

Lupunus

Striping (as in RAID 0) can be hazardous since a single disk failure can crash the whole RAID. That said, I ran a RAID 0 for about three years without problems. Implentation is also a factor in reliability.

The reason that I suggested a fifth drive in the optical bay is to keep the spindle count up without having to boot from the RAID. My rationale here is that if you are booting from the raid and the RAID controller dies, you have a serious data recovery problem.

The reason for the third party SATA III controller is to take advantage of the additional speed of the SATA III drives.

And the reason for suggesting RAID 5 is that it is both striped for speed and parity for reliability. Although you trade total capacity for reliability, total capacity isn't the OP's stated goal; and a 4-spindle SATA III RAID 5 is going to be a lot of fast...

I agree that knowledge is power if you're going to work with RAIDs. Understanding is probably why I've never lost any critical data to a RAID crash.

I have my R4 unit set in Raid 10. Speed test on the R4 are 220/200 write/read however copying files to and from internal 1TB HD on a new iMac maxes out at 130MBps which kinda *****....only twice faster than my FireWire HD. My data is super important but I would like to do Raid 0 and just rely on my Time Machine Backup. I have thought about putting a TM backup in Raid 1 so that I technically have 2 back ups but on a FW HD instead of using the R4 in any sort of backup mode. Would you recommend that when data is super sensitive?

I wish someone would post some real time copy speeds instead of speed test results. With my R4 unit 3/4 full (1.5TB out of 2TB, raid 10) I am getting about 150MBPS on the speed test but still a good 120MBps on copy and paste so there is some sort of bottle neck there. I'm guessing the internal HD. Would a Internal SSD improve the copy and paste to match the speed test? I just used the free blackmagic speed test from the App store.