Samsung SM951 (512GB) PCIe SSD Review
by Kristian Vättö on February 24, 2015 8:00 AM ESTAnandTech Storage Bench - Heavy
While The Destroyer focuses on sustained and worst-case performance by hammering the drive with nearly 1TB worth of writes, the Heavy trace provides a more typical enthusiast and power user workload. By writing less to the drive, the Heavy trace doesn't drive the SSD into steady-state and thus the trace gives us a good idea of peak performance combined with some basic garbage collection routines.
| AnandTech Storage Bench - Heavy | ||||||||||||
| Workload | Description | Applications Used | ||||||||||
| Photo Editing | Import images, edit, export | Adobe Photoshop | ||||||||||
| Gaming | Pllay games, load levels | Starcraft II, World of Warcraft | ||||||||||
| Content Creation | HTML editing | Dreamweaver | ||||||||||
| General Productivity | Browse the web, manage local email, document creation, application install, virus/malware scan | Chrome, IE10, Outlook, Windows 8, AxCrypt, uTorrent, AdAware | ||||||||||
| Application Development | Compile Chromium | Visual Studio 2008 | ||||||||||
The Heavy trace drops virtualization from the equation and goes a bit lighter on photo editing and gaming, making it more relevant to the majority of end-users.
| AnandTech Storage Bench - Heavy - Specs | ||||||||||||
| Reads | 2.17 million | |||||||||||
| Writes | 1.78 million | |||||||||||
| Total IO Operations | 3.99 million | |||||||||||
| Total GB Read | 48.63 GB | |||||||||||
| Total GB Written | 106.32 GB | |||||||||||
| Average Queue Depth | ~4.6 | |||||||||||
| Focus | Peak IO, basic GC routines | |||||||||||
The Heavy trace is actually more write-centric than The Destroyer is. A part of that is explained by the lack of virtualization because operating systems tend to be read-intensive, be that a local or virtual system. The total number of IOs is less than 10% of The Destroyer's IOs, so the Heavy trace is much easier for the drive and doesn't even overwrite the drive once.
| AnandTech Storage Bench - Heavy - IO Breakdown | |||||||||||
| IO Size | <4KB | 4KB | 8KB | 16KB | 32KB | 64KB | 128KB | ||||
| % of Total | 7.8% | 29.2% | 3.5% | 10.3% | 10.8% | 4.1% | 21.7% | ||||
The Heavy trace has more focus on 16KB and 32KB IO sizes, but more than half of the IOs are still either 4KB or 128KB. About 43% of the IOs are sequential with the rest being slightly more full random than pseudo-random.
| AnandTech Storage Bench - Heavy - QD Breakdown | ||||||||||||
| Queue Depth | 1 | 2 | 3 | 4-5 | 6-10 | 11-20 | 21-32 | >32 | ||||
| % of Total | 63.5% | 10.4% | 5.1% | 5.0% | 6.4% | 6.0% | 3.2% | 0.3% | ||||
In terms of queue depths the Heavy trace is even more focused on very low queue depths with three fourths happening at queue depth of one or two.
I'm reporting the same performance metrics as in The Destroyer benchmark, but I'm running the drive in both empty and full states. Some manufacturers tend to focus intensively on peak performance on an empty drive, but in reality the drive will always contain some data. Testing the drive in full state gives us valuable information whether the drive loses performance once it's filled with data.
The SM951 performs even strongly in our Heavy trace and presents nearly 100% improvement in data rate over the XP941. In full state the SM951 loses a bit of its performance, but that's normal and the drop isn't any bigger than in other drives. Despite the lack of NVMe, it's starting to be clear that the SM951 is significantly faster than its predecessor and any SATA 6Gbps SSD.
The average latency is also cut in less than half, which is actually a more substantial improvement than going from a SATA 6Gbps drive to the XP941.
The share of high latency IOs is also the lowest with only 0.06% of the IOs having a higher than 10ms service time.
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DanNeely - Tuesday, February 24, 2015 - link
"In any case, I strongly recommend having a decent amount of airflow inside the case. My system only has two case fans (one front and one rear) and I run it with the side panels off for faster accessibility, so mine isn't an ideal setup for maximum airflow."With the space between a pair of PCIe x16 slots appearing to have become the most popular spot to put M2 slots I worry that thermal throttling might end up being worse for a lot of end user systems than on your testbench because it'll be getting broiled by GPUs. OTOH even with a GPU looming overhead, it should be possible to slap an aftermarket heatsink on using thermal tape. My parts box has a few I think would work that I've salvaged from random hardware (single wide GPUs???) over the years; if you've got anything similar lying around I'd be curious if it'd be able to fix the throttling problem.
Kristian Vättö - Tuesday, February 24, 2015 - link
I have a couple Plextor M6e Black Edition drives, which are basically M.2 adapters with an M.2 SSD and a quite massive heatsink. I currently have my hands full because of upcoming NDAs, but I can certainly try to test the SM951 with a heatsink and the case fully assembled before it starts to ship.DanNeely - Tuesday, February 24, 2015 - link
Ok, I'd definitely be interested in seeing an update when you've got the time. Thanks.Railgun - Tuesday, February 24, 2015 - link
While I can see it's a case of something is better than nothing, given the mounting options of an M.2 drive, a couple of chips will not get any direct cooling benefit. In fact, they're sitting in a space where virtually zero airflow will be happening.The Plextor solution. and any like it is all well and good, but for those that utilize a native M.2 port on any given mobo, they're kind of out of luck. As it turns out, I also have a GPU blocking just above mine for any decent sized passive cooling; 8cm at best. Maybe that's enough, but the two chips on the other side have the potential to simply cook.
DanNeely - Tuesday, February 24, 2015 - link
Depends if it's the flash chips or the ram/controller that're overheating. I think the latter two are on top and heat sinkable.jhoff80 - Tuesday, February 24, 2015 - link
It'd be even worse too for many of the mini-ITX boards that are putting the M.2 slot underneath the board.I mean, something like M.2 is ideal for these smaller cases where cabling can become an issue, so having the slot on the bottom of the board combined with a drive needing airflow sounds like grounds for a disaster.
extide - Tuesday, February 24, 2015 - link
Yeah I bet it's the controller that is being throttled, because IT is overheating, not the actual NAND chips.ZeDestructor - Tuesday, February 24, 2015 - link
I second this motion. Prefereably as a seperate article so I don't miss it (I only get to AT via RSS nowadays)rpg1966 - Tuesday, February 24, 2015 - link
Maybe a dumb question, but: the 512GB drive has 4 storage chips (two on the front, two on the back), therefore each chip stores 128GB. If the NAND chips are 64Gbit (8GB), that means there are 16 packages in each chip - is that right?Kristian Vättö - Tuesday, February 24, 2015 - link
That is correct. Samsung has been using 16-die packages for quite some time now in various products.