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eSata speed difference on G-RAIDS?

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Thomas Morter-LaingeSata speed difference on G-RAIDS?
by on Oct 26, 2012 at 9:33:50 pm

A little bit more to this than the title, but I'll try and keep it as brief and tech specs only as possible:

I have 2 iMacs, both 3.4 Ghz i7 (late 2011), one has 12GB Ram and a 2TB Hitachi internal, one has 16GB Ram and a 1TB internal, Seagate. Both internal's get about the same read and writes.

Using a thunderbolt echo expresscard pro, and a Tempo Sata Pro (6GB) adapter. At home I have 3 G-Raids, all bought within a year of each other, all 2TB, all have about 50% free space.
At work I have the same, and if anything they actually have less space on them. However the G-RAIDs at work are getting consistent read/writes of 230/240MB/s, and the homes ones are hard pressed to push 220, and usually sit around 200. Whilst that extra 40MB/s might not seem a lot, its frustrating me and I want to know what I might be missing, is there a firmware update somewhere for anything that I may have at work? What on earth could possibly be slowing down all 3 of my G-RAIDS in comparison to the work ones?

Additional information:
Work computer running disksomnia 2, home running 3.
All OSX is same version (10.8.2)- the home version is a fresh install, the work one is upgraded from 10.7.
Disk speeds taken using blackmagic's free disk speed test app.

Any suggestions welcome!

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________
Editor, Certified Apple Product Proffessional, 2010
-------------------------------------------
Equipment (not for 'bragging', but in case it's relevant to future posts :D): Canon 7D, with Rode NTG2.
iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 2x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo ExpressCard/34 Thunderbolt adapter and Tempo™ SATA ExpressCard/34. Elgato Turbo H264HD.





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Chris GordonRe: eSata speed difference on G-RAIDS?
by on Oct 27, 2012 at 2:19:56 am

I'd check the exact specs of the drives inside the G-RAID enclosures. See if there are some different models that have different specs/performance.


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Thomas Morter-LaingRe: eSata speed difference on G-RAIDS?
by on Oct 27, 2012 at 2:38:14 am

Thanks, is there any easy way to do this at all?

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Chris GordonRe: eSata speed difference on G-RAIDS?
by on Oct 27, 2012 at 3:06:23 am

It depends on what g-technology has exposed (or hidden). DiskUtility will show what info is available on the exact model. Some makers hide or don't provide that specific info (very annoying). You can also pull up info in "About This Mac"'s System Information. I've never dealt with G-tech's enclosures and disks specifically, so I don't know what they do or don't provide.

The last resort is the screw driver and hopes there are actual labels on the disks with useful info.

There are only three disk manufacturers in the world now (Seagate, Western Digital and Toshiba). G-tech sources disks from one of these three to use in their enclosures -- hopefully they won't hide the details.


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 11:07:37 am

Don't Hitachi make drives? I'm pretty sure they make drives for Apple, and own G-Tech...

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 11:32:57 am

Hitachi's disk stuff was bought by WD. They are still running separately (making hitachi drives), but they are a WD company.

I'd open the chassis and see what you have in there.

Desktop (non-ES) drives will have issues with vibration. Other drives working in close proximity will cause latency issues for the heads. You will see this if you run "iosnoop -D" and watch the average latency on the reads.

If the drives aren't Hitachi, then you'll have higher latency relative to Hitachi Ultras. They are the best.

Steve Modica
CTO, Small Tree Communications


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 12:10:32 pm

Very very interesting, so the ones at work may indeed have slightly better internals, even if the difference is only tiny. Do you randomly know if there's a utility (windows or mac) that can give me some indication about what the internal drives are of these G-RAIDs? There a warranty sticker covering one of the screws :S

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 12:30:55 pm

[Thomas Morter-Laing] "Very very interesting, so the ones at work may indeed have slightly better internals, even if the difference is only tiny. Do you randomly know if there's a utility (windows or mac) that can give me some indication about what the internal drives are of these G-RAIDs? There a warranty sticker covering one of the screws :S"

The main difference is the rotational vibration sensor. That's what allows the drive to keep its latency down while operating in a ganged environment. One day, we'll all have SSDs and it won't matter :)

To figure the drives out, it depends on the hardware setup. If the drives are *on* the SATA bus and the OS can see them as individual drives (that are software striped) you can see them in the system profile. If they are sitting on their own bus (hardware raid), then the OS can't see them and no utility will be able to see them either. You'll need the RAID vendors utility. Atto will show you the drive info for example.

Steve Modica
CTO, Small Tree Communications


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 12:30:40 pm

when you run "iosnoop -D" (I had to run mine as sudo to allow it to work), how the heck am I supposed to make sense of the mountains of writing which happens after?

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 3:31:56 pm

[Thomas Morter-Laing] "when you run "iosnoop -D" (I had to run mine as sudo to allow it to work), how the heck am I supposed to make sense of the mountains of writing which happens after?"

DELTA UID PID D BLOCK SIZE COMM PATHNAME
218 0 83 W 434557744 4096 mds ??/68CF91E8/tmp.spotlight.state

This little snippet is the header that's printed along with one line of output. I trimmed the file path down a little to fit.

"DELTA" is the time it took to complete the IO. This is measured from the disk driver strategy routine to the driver interrupt routine (a very good indicator of the hardware speed). So this IO took 218 usec. The IO was issued by root (UID 0) and by process id 83 (mds daemon). It was a write command ("w") and it was 4096 bytes long.

If you start up an actual playout (or an IO benchmark) you can watch a little of this to get some idea if the disks are performing as you would expect.

For example, you would like to see all the IOs be very quick and about the same duration (give or take). If you see some jump way up, you might have a problem. It's easy to dump iosnoop's output into a file (iosnoop -D > filename) and then sort it later with "sort" to see if some IOs were really long.

iosnoop is part of the dtrace toolkit. It's eztremely useful and it's amazing that Apple ported it into MaC OS. That was huge.

Steve

Steve Modica
CTO, Small Tree Communications


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 3:49:43 pm

I'm sorry I now think your technical directions have far exceeded my knowledge :D I'm not sure exactly what Im suppose to do to measure the specifics of my G-RAIDs.
Although I did notice:

1139 501 354 W 313850674 4096 Disksomnia Help ??/G-RAID 001/.disksomnia
343 501 354 W 432419187 4096 Disksomnia Help ??/G-RAID 003/.disksomnia

That top one seems a touch slow? Or have I understood this totally wrong :S

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 3:53:31 pm

I wouldn't worry about things like this. Those are little configuration file touches. There's nothing going on there.

I'd run this while your benchmark app is running. Then you'll see some much larger time numbers and you can compare.

Steve Modica
CTO, Small Tree Communications


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 4:31:44 pm

Thanks very much, that makes sense. Are you saying I should compare with the numbers at my other imac and GRAID?

I'm getting numbers like
10024 501 1998 W 318081566 1048576 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp
and
10155 501 1998 R 317863890 286720 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp

Do you think theyre normal looking isn?

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 5:20:28 pm

[Thomas Morter-Laing] "10024 501 1998 W 318081566 1048576 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp
and
10155 501 1998 R 317863890 286720 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp"


This says that it takes about 10msec for an IO. These IOs are roughly 1MB and 256K. 10msec for 1MB isn't fast enough for uncompressed stuff, but it's OK for Pro Res. If all the IOs are 1MB, that's not usually very efficient (although it depends on your raids stripe size). We aim for 4MB.

Obviously one or two IOs isn't going to break a stream (the app reads ahead), but if you see a lot of smaller IOs that take 10msec, that's not a good thing. As you might imagine, doing a 4MB IO isn't going to take 40msec. It might finish in 16msec. That would mean roughly 4msec per MB instead of 10msec.

Steve

Steve Modica
CTO, Small Tree Communications


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Thomas Morter-LaingRe: Sata speed difference on G-RAIDS?
by on Oct 27, 2012 at 7:05:08 pm

Well its a G-RAID, so 2 1TB drives hardware striped together- isnt that about what I should expect from that level of hardware over esata? What would you suggest I do?

Tom Morter-Laing
Twitter- @TomTheEditor
_________________________________________________

iMac 27" intel i7 3.4GHz, 12GB RAM, ATI HD 6970M [2GB GDDR5], 3x G-Tech G-RAID (0) 2TB over Thunderbolt via Sonnet Echo Pro ExpressCard/34 Thunderbolt adapter and Tempo™ SATA Pro 6Gb ExpressCard/34.





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Steve ModicaRe: Sata speed difference on G-RAIDS?
by on Oct 29, 2012 at 1:49:03 pm

That's about right. I would expect 2 drives striped to max out at around 100MB/sec (minus overhead for parity and the bus). So 1MB in 10msec sounds right to me.

Steve Modica
CTO, Small Tree Communications


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