USB 3.0 RAID – Any increase in performance vs non-RAID USB drives?

[Tim Jones]

With USB 3, you can theoretically achieve 500MB/sec of I/O, so I’m not sure where they came up with the 245MB/sec unless it’s limited because they default it to RAID 5.

However, using RAID 0 (striping) with the 4 disks would be better since you would be able to get to around 300MB/sec to 400MB/sec easily (which doesn’t saturate the USB 3 bandwidth).

Remember, RAID 5 only protects if you have a disk failure, not if you overwrite or delete something, so be sure that you’re using a good backup workflow. And, if you’re backing up, I would recommend RAID 0 over RAID 5 for the added speed and capacity (1 disk worth).

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Mike Cohen]

[Tim Jones] ” And, if you’re backing up, I would recommend RAID 0 over RAID 5 for the added speed and capacity (1 disk worth).”

Yes I am looking for speed, not redundancy. I am a bit neurotic about backups and have my media on several offline drives for safe keeping.

Thanks

Mike

[Jeff Pulera]

Hi Mike,

I have the G-RAID 4TB USB 3.0 at home and it works well for multi-layer HD editing in CS6 (RAID 0).

RAID 0 combines two or more drives to work as one, so they will be faster than a single drive. USB 3.0 is not a bottleneck, performance should be as good as building an internal RAID 0 inside the PC.

The LaCie unit uses 4 drives compared to 2 for the G-RAID, so should be faster, and also offers the RAID 5 option for protection if desired. Not quite as fast as RAID 0, but protection is nice to have. With RAID 5, a 4TB unit formats to 3TB, 8TB provides about 6TB usable. Of course, RAID 0 provides full capacity but no fault protection – lose one drive and you lose all data in the RAID.

Thanks

Jeff Pulera
Safe Harbor Computers

[Tim Jones]

I need to dig further into the performance issue. Logic and aggregate disk performance imply that speeds over 400MB/sec should be achievable, but I don’t see it.

It turns out that we had the LaCie in the lab and I was able to run BM Disk Speed Test on it with my Mac Book Pro (4, 7200RPM Seagate Constellation .3 drives RAID 0) and it looks like the 245MB/sec claim is right on for bursting. Here’s the result I got after 25 runs (pic’s worth 1,000, and all that):

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Tim Jones]

I just moved the disks from the La Cie over to a SAS chassis – no change in formatting and the difference is astonishing, so there’s definitely something in the USB 3 layer that’s causing a reduction in I/O:

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Alex Gerulaitis]

[Tim Jones] ” there’s definitely something in the USB 3 layer that’s causing a reduction in I/O:”

Indeed. Areca’s new TB/USB 3.0 4-bay box (5026) is showing impressive numbers via USB 3.0: 350MB/s in RAID5. It’s not cheap though – and I am not sure how it achieves these numbers, there’s still some black magic in USB 3.0 adapters and their configuration: e.g. UAS is supposed to boost performance quite a bit, but very few boxes and adapters support it.

— Alex Gerulaitis | Systems Engineer | DV411 – Los Angeles, CA

[Mike Cohen]

So it appears that the USB 3.0 specification is “up to” XYZ mb/s, but in reality it is lower.

However the lower number still seems to be adequate for video throughput which is 35mb/s per stream for XDCAM for example, so 4 streams stacked would require roughly 140mb/sec which is well within the minimum reality throughput.

The speed of an individual drive vs a RAID 0, for example, would be improved also.

So which is higher, the USB data throughput, or the read/write ability of a 7200rpm drive?

[Tim Jones]

If you’re talking standalone drives, the USB 3 interface will be faster than the 115MB/sec you’ll see from a single drive. Of course, that means that you’ll see the full 115MB/sec on a USB 3 interface while USB 2 will only provide 43MB/sec from the same drive.

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Mike Cohen]

Thanks for all the useful information.

Mike Cohen

[Jeff Pulera]

Hi Mike,

Just to be sure we’re all on the same page, there are Megabits and there are MegaBytes, not to be confused.

Mbit = 1 million bits (Mb)
MByte = 8 million bits (MB)

Camera codecs are rated in Mb/s, while hard drive speed uses the 8x larger MB/s notation. Therefore, the 35Mb/s XDCAM codec really uses less than 5MB/s of bandwidth on a hard drive RAID that might be rated at 200MB/s, so definitely capable of playing more than a few streams…more like a few dozen streams.

Unless you plan on working with uncompressed HD, most any USB 3.0 drive, RAID or not, is capable of playing today’s compressed formats.

Using a simple Windows RAID 0 stripe set (two internal SATA drives) provides about 200MB/s and in Premiere CS6, I stacked up over 20 layers of AVCHD video (1080i at 24Mbps) as multiple PIPs and it played just fine!

Just wanted to put things in perspective. Perhaps too much concern is being put on actual drive speed versus theoretical maximum speed of the USB 3.0 interface when in reality, does it really matter for most editing needs?

Thanks

Jeff Pulera
Safe Harbor Computers