Slow SSD speed with OWC Mercury Elite Pro Dual

[DerKommissar]

Hi- in an effort to help my mid 2011 27in iMac limp along until the new Pro's are released I've bought a Crucial MX300 520 Gb SSD and put it in a OWC Mercury Elite Pro Dual enclosure connected over Thunderbolt. This is a massive improvement over my old, likely failing 1 TB HHD, but I'm only getting read/write speeds of 300/320 Mbs via AJA. The MX300 is not the fastest SSD, but I was expecting speeds more in the 400 Mbs range. I've swapped cables and had the same result, and I've tried hooking the enclosure up to a 2012 Air and gotten the same results via TB, and somewhat faster writes over USB 3 (380 Mbs- same read speeds). So, my questions are...

1) Is this really all I can expect from the drive given it's speed?
2) Is TB slower on the mid 2011 since it was one of the 1st to have the connection?
3) Is the OWC enclosure holding the drive back? I saw it's really only rated to about 450 Mbs, but I'm not evens seeing that.

If it matters, I do have the enclosure in port 1 (which provided a bump in write speed over port 2), and I have a 1680 x 1050 LCD on port 2. The SSD is about 44% full. I have the enclosure set up in JBOD mode with a 7200 1.5 TB drive in the second spot that I'm using for backups.

I got this open box for about $190, so it's pretty much the cheapest thing I could get. Other than the speeds I'm pretty happy with the flexibility, and it is faster than my older FW 800. I've not had any trouble with it so far. I bought it to avoid having to open my iMac and install it internally, and I'd still prefer to avoid that.

 

[nambuccaheadsau]

Try it externally without the enclosure. When I had a 2011 iMac, I purchased a Silicon Power 240GB TB Drive, and just hooked it up via TB and sat the drive on a Twelve South BackPack Rack, cloned the internal over to it, into System Preferences > Startup Disk and select it to boot from and away you go.

Worked perfectly with speeds in the high 400's.

 

[danielwsmithee]

Based on this information from OWC's website my guess is there is a limitation in the performance of the chipset in the enclosure...

* 1) When the enclosure is set to Independent drive mode, only the drive in HDD2 is bootable.
2) Independent drive mode is not fully supported by some versions of Mac OS X when connected over Thunderbolt. In Mac OS X 10.8.3 and prior, only HDD2 appears. This is a limitation of of the operating systems' support for the SATA chipset in the Mercury Elite Pro Dual. Independent drive mode does not have the limitation when used over USB.
​

I would suggest pulling out the SATA HD and see if you get better individual performance.

 

[DerKommissar]

Thanks- I tried that, and while booting is slower with the HD, there are no differences in benchmarks. There is definitely something odd about the chipset that OWC is using here, but it should have the overhead to get this SSD closer to its peak performance. Maybe I'll get board and install the SSD internal so I can know for sure. Anyway, it's still faster than the internal HD and is fine for everyday use. It's just bugging me that it's pretty clear that the OWC Mercury Elite Pro has some limitations that prevent SSDs from reaching their max speeds.

Based on this information from OWC's website my guess is there is a limitation in the performance of the chipset in the enclosure...

* 1) When the enclosure is set to Independent drive mode, only the drive in HDD2 is bootable.
2) Independent drive mode is not fully supported by some versions of Mac OS X when connected over Thunderbolt. In Mac OS X 10.8.3 and prior, only HDD2 appears. This is a limitation of of the operating systems' support for the SATA chipset in the Mercury Elite Pro Dual. Independent drive mode does not have the limitation when used over USB.
​

I would suggest pulling out the SATA HD and see if you get better individual performance.

 

[nambuccaheadsau]

Did you try the SSD without the enclosure. It is not needed.

 

[DerKommissar]

The point of the enclosure is that I did not want to open my iMac and take the risk of doing it poorly. I understand how to install it internally, but given all published specs, I expected similar performance from an external Thunderbolt enclosure. I may do so sometime in the future out of curiosity, but spending the money on the enclosure and all the stuff needed for internal install makes buying the enclosure harder to justify. If the SSD can perform better in USB 3 than in TB mode, does that not imply that the controller is holding the SSD back?

After rereading your comment, how exactly do you propose that I hook up the SSD externally without 1) the current enclosure or 2) spending more money on another enclosure?

If I spend more money, it will be to install it internally and just be done with it. The TB enclosure is faster than my old FW800 one, so at least backups will be faster, but the money spent will still be somewhat wasted.

Did you try the SSD without the enclosure. It is not needed.

 

[satinsilverem2]

I have the same enclosure with two 1TB Samsung 850 EVO SSDs in RAID 0 and I don't get more than about 380 writes and 390 reads. I think its a limitation of the enclosure.

 

[DerKommissar]

Thanks for the info- that's about what I expected. I guess I should have read the fine print before I bought. One would reasonably expect, for that kind of money, that a device sold on the basis of having a Thunderbolt connection would be able to take full advantage of it. I'd like to return it, but I don't really want to go through the hassle.

I have the same enclosure with two 1TB Samsung 850 EVO SSDs in RAID 0 and I don't get more than about 380 writes and 390 reads. I think its a limitation of the enclosure.

 

[satinsilverem2]

Thanks for the info- that's about what I expected. I guess I should have read the fine print before I bought. One would reasonably expect, for that kind of money, that a device sold on the basis of having a Thunderbolt connection would be able to take full advantage of it. I'd like to return it, but I don't really want to go through the hassle.

that product if I remember correctly was one of the first thunderbolt enclosures from OWC and used a first generation chipset so I'm not all that surprised about the performance. Ive been very happy with mine the only thing thats gone wrong with it was a fan went out but OWC replaced it no problem.

 

[DerKommissar]

They've taken the page down, so I can't verify the numbers, but I think you are correct. I bought it as an open box, last one they had left. If I'd known it would be this restrictive (306 Mbs sequential reads on a modern SSD are pretty low), I would have spend the extra $30 to get the open box TB 2 model. I'm working with an OWC support person right now trying to verify the max speed of the enclosure. I'd accept 380 Mbs read and writes over TB if this enclosure can produce that.

that product if I remember correctly was one of the first thunderbolt enclosures from OWC and used a first generation chipset so I'm not all that surprised about the performance. Ive been very happy with mine the only thing thats gone wrong with it was a fan went out but OWC replaced it no problem.

 

[danielwsmithee]

OWC is usually pretty good to work with. If you ask nicely and complain enough they might let you pay the price difference minus restocking fee to upgrade to an OWC Thunderbay 4 or 4 mini...

 

[nambuccaheadsau]

Why spend the extra cash when your iMac can only run TB 1?

 

[724699]

The OWC enclosures don't use the best chipset - you'll find it won't max out the TB connection, even over TB1 (10gb/s). You'd need something like an Akitio TB2 dual bay enclosure.

I found the same limitations when I purchased a little StarTech Thunderbolt DUO enclosure. Was cheap (comparably), and does the job for me as I only needed 2 individual drives and not RAID; but this thing uses the same internals - it's not making full use of my SSD speeds and tops out at 390MB/s approx.

Eventually if I just can't stand the max speeds (which is doubtful as I only use it as external storage for apps and movies etc., and TimeMachine backups - so don't hammer it with data very often) I'll replace it. It is kind of a bummer to spend money on a faster drive and see less than its max performance when you go for a TB enclosure which is more than capable of reaching those speeds. Oh well!

 

[DerKommissar]

Thanks, Chorner- I clearly jumped into this too quickly and did not do my due diligence. Honestly, it's fast enough to run as my boot drive while also hosting my Time Machine backups, so I guess I can't really complain. I do wish I was at least getting 390 Mbs like you are. I agree that it feels off to not be using the SSD to its full potential, but I admit I have no practical need for the extra speed so far. I guess when I get tired of it I'll install the SSD internally and use the enclosure just for backups and extra storage. But either way, hopefully these posts will warn others who are thinking they can get full speed out of OWC enclosures. I would not buy another one knowing what I know now. It's pretty damn dumb that something that costs almost $300 new without any drives can't do better than 300 Mbs over thunderbolt.

 

[Oldmanmac]

For me. OWC is a jok! Several years ago I bought 2 FW enclosures. Never could get them to work right. Nor was I able to get refund.
BUYER BEWARE!

 

[cynics]

Why spend the extra cash when your iMac can only run TB 1?

Its the fastest external option available for them.

 

[724699]

Thanks, Chorner- I clearly jumped into this too quickly and did not do my due diligence. Honestly, it's fast enough to run as my boot drive while also hosting my Time Machine backups, so I guess I can't really complain. I do wish I was at least getting 390 Mbs like you are. I agree that it feels off to not be using the SSD to its full potential, but I admit I have no practical need for the extra speed so far. I guess when I get tired of it I'll install the SSD internally and use the enclosure just for backups and extra storage. But either way, hopefully these posts will warn others who are thinking they can get full speed out of OWC enclosures. I would not buy another one knowing what I know now. It's pretty damn dumb that something that costs almost $300 new without any drives can't do better than 300 Mbs over thunderbolt.

I agree. The price point it commands because of the Thunderbolt connectivity really turns out to be a bit of a sham. May as well use USB 3, though I may argue that the stability of transfers and the nicer looking cables count for something? lol once I accepted that I saved a couple hundred on the enclosure vs an Akitio or something else, and only use it for light duty backups and storage in JBOD mode... I appreciate the compact design, and overall enclosure itself. Lowered expectations on max thoroughput unfortunately

Trouble is, there are very few suppliers out there for diskless Thunderbolt enclosures. There's only expensive and slightly less expensive, but the difference between the top models is larger than the price would suggest in terms of quality IMO.

 

[nambuccaheadsau]

No USB3 on a 2011 iMac. That came in with the next year's models.

 

[DerKommissar]

Its the fastest external option available for them.

All of these enclosures from OWC are held back by their chipset, not the TB interface. The ThunderBay enclosures have TB 2, but they also have the fastest chipset. Even the Mercury elite pro that supports TB 2.0 is limited by a chipset that only allows transfers up to 490 Mbs. The Akito boxes seem to all have better chipsets that support faster speeds. What I'm ticked about is that while OWC is upfront about the speeds of their enclosures for the most part, nowhere on their product page for the TB1 version of the Mercury elite pro do they list how low the cap is for that product (less than 400 Mbs).

 

[winston1236]

It's probably your configuration, looking at the specs on the OWC site they show a RAID 0 config as being the single fast config.

They don't list any actual numbers, instead using a 1 to 5 rating with RAID 0 being 5/5 and all other configs being 2/5.

 

[DerKommissar]

It's probably your configuration, looking at the specs on the OWC site they show a RAID 0 config as being the single fast config.

They don't list any actual numbers, instead using a 1 to 5 rating with RAID 0 being 5/5 and all other configs being 2/5.

Did you read the rest of the post? I've two other computers and gotten the same results. I've tried different cables and gotten the same results. I've tested with and without an additional HD on the same bus. It's either the drive or the enclosure, and the drive benchmarks around 500 Mbs for reads and writes. Plus, writes are 60 Mbs faster when hooked up by USB 3, suggesting that the drive has more potential than the enclosure is allowing. The bus is capable of 10 Gbs, but the devices that use the bus have to be capable of that too, and I do not think the chipset in this OWC enclosure is capable of it.

 

[danielwsmithee]

Did you read the rest of the post? I've two other computers and gotten the same results. I've tried different cables and gotten the same results. I've tested with and without an additional HD on the same bus. It's either the drive or the enclosure, and the drive benchmarks around 500 Mbs for reads and writes. Plus, writes are 60 Mbs faster when hooked up by USB 3, suggesting that the drive has more potential than the enclosure is allowing. The bus is capable of 10 Gbs, but the devices that use the bus have to be capable of that too, and I do not think the chipset in this OWC enclosure is capable of it.

I think what he is getting at is that this particular chipset, and most of them used in dual drive enclosures, are generally intended to be used in a Raid 0 or Raid 1 configuration. While they function in JBOD, their performance suffers. Just my guess, it would be interesting to see a benchmark of the performance of this enclosure with two SSDs in Raid 0.

It wouldn't surprise me if there is a hardware resource in the chipset that is shared between the two interfaces in JBOD mode that causes decreased performance. In Raid 0 or 1 that one resource is dedicated to the one logical volume...

 

[winston1236]

I think what he is getting at is that this particular chipset, and most of them used in dual drive enclosures, are generally intended to be used in a Raid 0 or Raid 1 configuration. While they function in JBOD, their performance suffers. Just my guess, it would be interesting to see a benchmark of the performance of this enclosure with two SSDs in Raid 0.

It wouldn't surprise me if there is a hardware resource in the chipset that is shared between the two interfaces in JBOD mode that causes decreased performance. In Raid 0 or 1 that one resource is dedicated to the one logical volume...

Exactly, that's what I was referring to about the Raid 0/1. I would love to see the results of a test with the Raid 0 with dual SSDs. I think you're right about the shared resource slowing speeds, that would be a logical explanation for it.

 

[DerKommissar]

Interesting- I guess its a possibility. Why would performance still suffer in JBOD without the 2nd drive attached, however? One would think performance would improve.

Anyway, I've talked to OWC, and they consider the performance normal, so I either keep it or replace it. I don't think I'll really notice a faster enclosure outside of benchmarks (and maybe when both drives are being accessed), so I'm going to sit tight for a while and hope there's a good mini upgrade in the future (or that there's a entry level Mac Pro like they used to do) and use the enclosure for backups.

 

[Andrewewe]

need help, SSD problem?