jedH

Best interface for the fastest 7.2k drives; FW800 or Gigabit?

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Correct me if I'm wrong...

But I believe that the STR for the fastest 3.5" 7.2k drives is 95MB/s & that in some instances they can hit 125MB/s.

This is not 100% verified yet, but by-all-accounts FW800 enclosures only hit 60MB/s.

I wouldn't expect them to hit FW800's theoretical maximum, but 60MB/s? Come on!!

Because I use Wifi for internet connectivity I've realised I have one other option on my mac mini (oct 09); Gigabit

Is it possible to get higher throughput via an enclosure using a Gigabit interface?

If not...

If I got an enclosure that only transferred at 60MB/s, is it total overkill to get a drive with a STR of 95MB/s?

Or could there be certain applications/instances where it may still be advantageous?

It has to be FW800 or Gigabit, as that's the only interfaces my Mini has :-(

Cheers

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You can get 100MB/sec or more real-world out of GigE. I don't know if the Mac Mini's implementation is that fast or if your chosen enclosure can get that fast, though-- there's more variables than just that.

Considering that faster harddisks also tend to mask latency better, of course you would want a faster drive. :)

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pretty sure the mini is, the enclosure will be the big question mark, have you ever looked at these sort of enclosures?

What did you mean in that last sentence, sorry 430am, bed time :D

You can get 100MB/sec or more real-world out of GigE. I don't know if the Mac Mini's implementation is that fast or if your chosen enclosure can get that fast, though-- there's more variables than just that.

Considering that faster harddisks also tend to mask latency better, of course you would want a faster drive. :)

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No, I haven't. I have a few small NAS's here but I have never benchmarked performance.

Considering you can't get a slower harddisk anyway, why bother looking for one? :P

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Well it's faster than fw800 enclosures, most seem to top out at 80MB/s.

Maybe Gigabit enclosure will end up being the same, hope not... :-(

Which I guess brings me back to my original Qn:

If I got an enclosure that only transferred at 80MB/s, is it total overkill to get a drive with a STR of 95MB/s?

Or could there be certain applications/instances where it may still be advantageous?

goodnight, or morning i should say, 5am & off to bed...yikes

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If I got an enclosure that only transferred at 80MB/s, is it total overkill to get a drive with a STR of 95MB/s?

Or could there be certain applications/instances where it may still be advantageous?

If STR is your only concern, then yes, it's over kill.

BUT, what about IOPS. Drives with higher STRs, will also typically have higher IOPs (be it single-user or multi-user orientated), so while you may max out the STR on say reading a single 200MB file, you will still have plenty of room for random IO stuff (when the disk is the bottleneck and not the interface), where you may have 1000's of 4K reads and writes spread across the disk. What I'm trying to get at, is that STR is not the only measure of performance (and many would argue that it serves as a poor benchmark metric), and that IOPs for your given task should be the consideration as well.

PS. I live in a world where STR means nothing, but random IO is king.

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Great, so it sounds like another important facet will also be hamstrung by 80MB/s :-(

Have you had any experience with external enclosures & compared Gigabit to FW800?

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Great, so it sounds like another important facet will also be hamstrung by 80MB/s :-(

Have you had any experience with external enclosures & compared Gigabit to FW800?

Umm, current top model drives that have to do 1000's of random 4K reads generally top out at 20-30MB/s ???

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yes the faster 7.2k drives will do 60-130Meg/s STR

xp/vista over gigabit ethernet can do >100Meg/s if configured correctly

most cheap NAS's with gigabit ports will find it hard to even get 40Meg/s, similar to USB speeds

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You're referring to NAS devices, I'm referring to direct attached (block level) devices usually augmented by protocols such AoE.

In those scenarios it is possible to get 100MB/s+ ....

Only problem being....

I don't think I'm going to find a single drive enclosure with the required support, it's all enterprise stuff :-(

And even if I do, there isn't support in EFI to use Gigabit attached drives as boot/system volumes :-(

So it's looking like Fw800 is really my only option, sigh....

So I guess I'll just get a green drive that doesn't burst beyond 80MB/s (that right?) ...

Cheers

Great, so it sounds like another important facet will also be hamstrung by 80MB/s :-(

Have you had any experience with external enclosures & compared Gigabit to FW800?

Umm, current top model drives that have to do 1000's of random 4K reads generally top out at 20-30MB/s ???

Edited by jedH

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On the upside slower 7.2k (GP?) + FW800 should still be faster than the 5.4k 160GB 2.5" HDD in my Mac Mini (Oct 09).

Anyone have any idea what sort of speeds they attain? STR, IO/s etc...

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sorry i misread that statement, you were referring to drives, not NAS's...

Umm, current top model drives that have to do 1000's of random 4K reads generally top out at 20-30MB/s ???

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Can I get confirmation that the highest 7.2K drives can burst nowadays is 115MB/s & that the highest STR is 90MB/s?

I've had others claim that STR is nowhere near that and that burst doesn't go above 80MB/s, meaning that FW800 is totally fine!

I'm in the midst of finding more about Gb/AoE/enclosures, & Gb boot volumes w/EFI, I'll keep you informed of my findings..

3:30am, good night

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Can I get confirmation that the highest 7.2K drives can burst nowadays is 115MB/s & that the highest STR is 90MB/s?
wow, where the hell did you hear that?

Why are you so worried about harddisk bursts and STR?

Even if you're interface limited-- and for a modern 7200rpm drive on Firewire800 you are going to be interface limited, the faster drive isn't going to hurt anything, and with harddisks being so cheap today it's not worth deliberately buying a slower one because it won't save you any significant amount of money. As stated above the reason to have a faster disk is to help mask latency, since harddisks measure latency in milliseconds, which is orders of magnitude slower than the nanosecond latency measured in fastest parts of the rest of the system.

http://www.techreport.com/articles.x/17812/7

Shows burst speeds up to 232MB/sec and the slowest average read is 84MB/sec, which means at the beginning of the platter the drive is probably still doing well over 100MB/sec.

http://www.xbitlabs.com/articles/storage/d...up_6.html#sect0

http://www.xbitlabs.com/articles/storage/d...dd-roundup.html

upside slower 7.2k (GP?) + FW800 should still be faster than the 5.4k 160GB 2.5" HDD in my Mac Mini (Oct 09).
WD's GreenPower disks are 5400rpm, Seagate's Barracuda LP disks are 5900rpm.. they're NOT 7200rpm. But yeah, they are probably marginally faster than a new high-density laptop disk. I'm not sure what configuration your 160GB disk uses internally so I can't say for sure.

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So you're suggesting that despite the interfaces not having the bandwidth, the extra speed of the faster 7.2ks around is still beneficial?

Not sure I see how?

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Correct. It helps to mask latency (access time).

If your computer needs a chunk of data and it's not in the buffer, then the disk has to spin to get it. That takes up to 15ms, which is a freakin' eternity when the rest of the system is capable of memory access in as fast as 50 nanoseconds or so. So by buying the fastest possible harddisk you can justify, even if you are interface bandwidth limited, there's still all sorts of occasions where you are more latency limited. (crude example) If you can shave 3ms off of 15ms by having the heads move less on the harddisk to get to the data you need, and then to actually read the data (call it 8MB) takes only 0.084 seconds (assuming 100MB/sec STR) instead of 0.114 seconds (assuming 70MB/sec STR), you are still talking an eternity in computer time.

And there's no such thing really as "faster" 7200rpm disks; the costs of a 500GB/platter 7200.12 500GB or 1TB is pretty much the same as an older, slower disk if you are buying new, so again, why buy a slower disk?

If you need another analogy, think about a lazy susan at a dinner table. Sure, you can only eat so much food fast... but the faster you can spin the lazy susan to get to the next dish you know you already want, the less time you have to wait. And the plate sitting in front of you is your "buffer", so more of the time you can keep that buffer full, the better.

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Heh, love the analogies, makes total sense, thanks! I'm prolly going to buy two 500GB disks...

As I want to add the 2nd one to a pre-existing enclosure I have, & hang that enclosure off a 2nd (much older) Mac Mini.

500GB/platter is as dense as it gets nowadays isn't it? Do the 500GB drives lose out in the speed dept compared to the 1TB drives?

I'd assume a single 500GB platter would be more efficient than two 500GB, but two 500GB may have other unforeseen advantages.

Thanks for your insights!

-jed.

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500GB/platter is as dense as it gets right now.

The highest-capacity disks usually have the best performance as they can keep more data on the fastest part of the disk (e.g. the fastest 10% of the platter in a 1-platter 500GB/platter disk = 50GB; the fastest 10% of the platters in a 2-platter 500GB/platter disk = 100GB). The heads also have to move less as a result.

Granted you are usually splitting hairs at this point. :)

(with say 50GB of data I doubt you'd notice outside of synthetic benchmarks unless it's extremely sequential-transfer-heavy, but with say 400GB of data you might see more benefit-- as you can tell from testing the slowest part of the disk is indeed considerably slower than the fastest part).

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Cool that's not a biggy,

I'd be surprised if the boot/system volume gets anywhere near 400GB within the next yr...

At which point the internal 2.5" will be swapped-out for a SSD, & the external will become the backup volume!

Thanks heaps for your advice, much appreciated.

-jed

Edited by jedH

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Seems like they are for desktop use, although the bit-tech.net review says the new Samsung F3's are even faster. I haven't seen enough independent reviews or used any of them enough to make my own assessment.

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