Samsung SSD XP941 Review: The PCIe Era Is Here
by Kristian Vättö on May 15, 2014 12:00 PM ESTFinal Words
I don't think there is any other way to say this other than to state that the XP941 is without a doubt the fastest consumer SSD in the market. It set records in almost all of our benchmarks and beat SATA 6Gbps drives by a substantial margin. It's not only faster than the SATA 6Gbps drives but it surpasses all other PCIe drives we have tested in the past, including OCZ's Z-Drive R4 with eight controllers in RAID 0. Given that we are dealing with a single PCIe 2.0 x4 controller, that is just awesome.
The only major problem in the XP941 is that it doesn't support booting in most Windows systems. If you are a Mac Pro owner, this issue doesn't concern you but for everyone else it's definitely a major drawback. Using an SSD as a secondary drive can make sense for e.g. a video professional where the performance can be utilized as a scratch disk, but otherwise the only real use case for an SSD is as a boot drive. There is hope that 9-series motherboards will bring better support for native PCIe booting but that remains to be seen.
The lack of proper TRIM support is also a minor concern but I'm willing to overlook that because the performance is just so great. I would also like to see hardware encryption support (TCG Opal 2.0 & IEEE-1667) and power loss protection but I understand that for an OEM product, these aren't necessary. Hopefully there will be retail versions of XP941 that address these items.
| 120/128GB | 240/256GB | 480/512GB | |
| Samsung SSD XP941 | ~$229 | ~$310 | ~$569 |
| Plextor M6e | $180 | $300 | - |
| OCZ RevoDrive 350 | - | $530 | $830 |
Note that the XP941 prices in the table above do not include the adapter or shipping. The adapter comes in at around $25 and RamCity charges $29 for shipping overseas, so you are looking at about $55 in addition to the drive itself. However, you don't have to pay the 10% Goods and Services Tax (GST) when purchasing from overseas and I've already subtracted the GST from the listed prices in the table above. To summarize, the total cost with the adapter and shipping included ends up being about $283 for 128GB, $364 for 256GB and $623 for 512GB. In the end the exact pricing depends on the AUD to USD ratio and banks may also charge a bit if paying with foreign currencies.
In terms of pricing, the XP941 is a steal compared to the competition. The M6e is cheaper but it's also only PCIe 2.0 x2 design and can't offer the same level of performance as the XP941 can. Of course, ultimately two or three SATA 6Gbps SSDs in RAID 0 would be the cheapest route but with RAID 0 you run into other issues (such as increased risk of disk failure). For the average user, I'd still recommend a drive like Samsung SSD 840 EVO or Crucial M500/M550 but I can certainly see the enthusiast and professional crowd paying the premium for the XP941.
All in all, I can't wait for Samsung to release a retail version of the XP941. Right now the only problems are the limited availability and lack of boot support but once these are sorted out, the XP941 will be the king of the market. I'm guessing that we'll probably see something from Samsung at this year's Global SSD Summit, or at least I deeply hope so. We'd also like to see more competition from other SSD manufacturers, but until SandForce's SF3700 is ready to hit the market in the second half of 2014, there isn't a drive that can challenge the XP941.
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McTeags - Thursday, May 15, 2014 - link
I think there is a spelling mistake in the first sentence. Did you mean SATA instead of PATA? I don't know all of the tech lingo so maybe I'm mistaken.McTeags - Thursday, May 15, 2014 - link
Please disregard my comment. I googled it...BMNify - Thursday, May 15, 2014 - link
sata-e[serial], sata[serial], pata[parrallel] ,SCSI [several, and chainable to 15+ drives on one cable, we should have used that as generic] ,shugart these are all drive interfaces and there are more too going back in the day....metayoshi - Thursday, May 15, 2014 - link
"It's simply much faster to move electrons around a silicon chip than it is to rotate a heavy metal disk."While SSD performance blows HDDs out of the water, the quoted statement is technically not correct. If you take a single channel NAND part and put it up against today's mechanical HDDs, the HDD will probably blow the NAND part out of the water in everything except for random reads.
What really kills HDD performance isn't the just rotational speed as much as it is the track-to-track seek + rotational latency of a random workload. A sequential workload will reduce the seek and rotational latency so much that the areal density of today's 5 TB HDDs will give you pretty good numbers. In a random workload however, the next block of data you want to read is most likely on a different track, different platter, and different head. Now it has to seek the heads to the correct track, perform a head switch because only 1 head can be on at a time, and then wait for the rotation of the disk for that data block to be under the head.
A NAND part with a low number of channels will give you pretty crappy performance. Just look at the NAND in smartphones and tablets of today, and in the SD cards and USB thumb drives of yesteryear. What really makes SSDs shine is that they have multiple NAND parts on these things, and that they stripe the data across a huge number of channels. Just think RAID 0 with HDDs, except this time, it's done by the SSD controller itself, so the motherboard only needs 1 SATA (or other like PCIe) interface to the SSD. That really put SSDs on the map, and if a single NAND chip can do 40 MB/s writes, think about 16 of them doing it at the same time.
So yes, there's no question that the main advantage of SSDs vs HDDs is an electrical vs mechanical thing. It's just simply not true that reading the electrical signals off of a single NAND part is faster than reading the bits off of a sequential track in an HDD. It's a lot of different things working together.
iwod - Friday, May 16, 2014 - link
I skim read it. Few things i notice, No Power usage testing. But 0.05w idle is pretty amazing. Since the PCI-E supply the power as well i guess they could be much better fine grained? Although Active was 5.6W. So at the same time we want more performance == faster controller while using much lower power. it seems there could be more work to do.I wonder if the relative slow Random I/O were due to Samsung betting its use on NVMe instead of ACHI.
iwod - Friday, May 16, 2014 - link
It also prove my points about Random I/O. We see how Random I/O for xp941 being at the bottom of the chart while getting much better benchmarks results. Seq I/O matters! And It matters a lot. The PCI -E x4 interfaces will once again becomes bottleneck until we move to PCI-E 3.0 Which i hope we do in 2015.Although i have this suspicious feeling intel is delaying or slowing down our progression.
nevertell - Friday, May 16, 2014 - link
Can't you place the bootloader on a hard drive, yet have it load the OS up from the SSD ?rxzlmn - Friday, May 16, 2014 - link
'Boot Support: Mac? Yes. PC? Mostly No.'Uh, a Mac is a PC. On a serious tech site I don't expect lines like that.
Penti - Friday, May 16, 2014 - link
Firmware differences.Haravikk - Friday, May 16, 2014 - link
It still surprises me that PCs can have so many hurdles when it comes to booting from various devices; for years now Macs have been able to boot from just about anything you plug into them (that can store data of course). I have one machine already that uses an internal drive combined with an external USB drive as a Fusion Drive, and it not only boots just fine, but the Fusion setup really helps eliminate the USB performance issues.Anyway, it's good to see PCIe storage properly reaching general release; it's probably going to be a while before I adopt it on PCs, as I'm still finding regular SATA or M.2 flash storage runs just fine for my needs, but having tried Apple's new Mac Pros, the PCIe flash really is awesome. Hopefully the next generation of Mac Pros will have connectors for two, as combined in a RAID-0 or RAID-1 the read performance can be absolutely staggering.