Samsung SSD guide

Introduction

as far as I know there is no comprehensive overview of the Samsung SSD portfolio.

This is a bit of a problem since there is a also a high variety of models.

Single letters can bear a lot of meaning, i.e. a 5x performance difference or no cache protection.

This will give you an overview of the more recent and future models and how they differ.

                             

How to read

(10k) - Number from a datasheet if it is different from either brochures, other datasheets or benchmarks.

6k-15k - Lower number for smaller capacity models, higher number for 460GB+ models that have full internal bandwidth.

Write IO/s in steady state - Look at this column for intense use / if you need stable operation with few latency spikes.

Any datasheet and brochures I could find is linked to (hover over the SSD model).

Samsung SSD overview                                                               

Model / brochure & datasheet linkInterface TypeLink SpeedFlash TechnologyRead MB/sWrite MB/sRead IO/sWrite IO/sWrite IO/s in steady stateCache ProtectionOEM only modelBest use
830SATA6MLC520160-40080k16k-36k2knonoDesktop
PM830mSATA6MLC50090-26080k16k-36k2knoyesLaptop (or maybe embedded)
SM825, datasheetSATA3eMLC26023543k (35k)5.5k-11k (10k)5.5k-10kyesunknownlow-medium spec DB server, Proxy, Ceph Journal (low Bandwith, good latency)
840SATA6TLC530130-33086k-92k32k-70kunknownnono (this model seems to be out of market)Desktop
840 EVOSATA6TLC / SLC buffer540410-520100k32k-90k3.3knonoDesktop, Highspeed File Store (SOHO, etc)
840 PRO, datasheetSATA6MLC530390-520100k80k7knonoHighend Desktop, SW build server
PM843TSATA6TLC520330-41060k (87k)

2.5k

(15k)

2kyesyesWebserver (<10% write)
SM843TSATA6eMLC49036070k - 89k11k (13k)11kyesyeslow-medium DB Server, Nagios Server, SW build server (0.83PW write)
SM843TnSATA6MLC53036082k10k (13k)10k very very yes"high endurance" / high random IO (20-30% write), (4PB write)
SV843SATA63D V-NAND53043089k35k14kyesyes40-50% write (20PB write)
SM1625Dualport SAS6G (x2)eMLC848740101k38k38kyesunknownbusy DB server, Ceph Journal (high IOPS hosts, can probably get on top of Intel DC S3700), Flashcache.
SM1623 (new)SAS   950520 120k 26k  unknown 
850 PROSATA63D MLC V-NAND550470-520100k90k9k?nonoHighend Desktop
850 EVOSATA63D TLC-VNAND54052094k88-90k6.5knono 
950PROM.24x 25001500      
PM851 brochureSATA6TLC540270-410100k100k? unknownunknown"Mobile/Client"
845DC EVOSATA6TLC (w. SLC buffer)530270-41087k12k-14k12k-14kyesno (but not for sale yet)File Servers, Web Servers
845DC PROSATA63D MLC V-NAND53046092k50k49kyesno (but not for sale yet)VPS Hosts, lowend DB Server, Proxy, Ceph Journal (high capacity Ceph setup), Flashcache with limited hot data set.
PM853TSATA6TLC530270-41090k14k14kyesyes (OEM version of 845DC EVO)File Servers, Web Servers
XM1715SAS12        High endurance
XS1715

SFF-8639 / NVMe

4xeMLC30001400750k115k115k?

yes

no"Class dominating read performance"
SM1715

PCIe 3.0 / NVMe

4x (20gbps)3D (MLC) V-NAND30002200750k (740k?)

180k (130k)

unknownyesyesHigh throughput databases, crazy stuff
XP941PCIe 3.0/NVMe4xMLC1000-1170450-950122k72k(9k?) yes 
XP951PCIe/M.24x 2150155085k?130k?  yesInfo on this SSD is still questionable
SM951PCIe3.0/NVMe4x 16001000130k100k  yes

Info on this SSD is still questionable

SM863SATA and PCIe3.0/M.26 / 4x 32Gbps)3D V-NAND52048597k12k-29k yesyesHigh endurance (6PBW)
PM1633aSAS12g3D V-NAND       16TB model
PM863PCIe3.0/M.24x (32Gbps)V-NAND?20001200450k40k (max)  yes

could not yet find specs for the M.2 edition. 1.3DWD for this version.

(1.33-5.466PBW)

3.84 TB model only in 2.5" casing

OEM models - I learned about those via reference of PureStorage's all flash arrays ("AFA"). Since they have protected caches I almost immediately went out and ebayed one. Yesterday I learned they aren't for public sale and this "could" be a hunch they won't support them with new firmware for home users to download. Also consider: If this is OEM only, how trustworthy is the company selling them to you as an end user / integrator? Anyway, If I'm offered a cheap Dell C6220 fully loaded with them, I won't ask twice... heck, why would I :)

SM825 - Different numbers are floating for this models' IOPS. The ones in braces are from the brochure, the other ones from the datasheet and a review.

T = Tantalum Capacitor. There are other models. Beware the PM/SM843 models that don't have a suffix. The SV843 on the other hand does have a capacitor.

SLC buffer = as far as I understood, the SSD uses different adressing modes to the cells. A staging area is "used like SLC" - or if I misunderstood, there's actually a few gig of SLC. It is later backfilled onto the TLC area. As long as you have sufficient non-write times, this is elegant and should work well. 

845DC EVO is said to be 21nm, 853T is said to be 10nm or 19nm Unverified, no datasheets on the whole new series yet as their announcements were only made between june and early july.

845DC PRO vs. 853T: According to storagereview.com benchmarks the SM853T has a little lower latency, This could also be caused by difference RAM sizes (512MB on 400GB  / 1024MB on 960GB)

SM823 is the successor of the SM1625, but take note the write performance is supposedly >20% lower.                         

                    

If you're interested in the 845DC EVO, tell your sales rep they should consider a 2TB model - every server I know can fit a "fat" SSD just as well as a slim 5 millimeter one. There's space for a double capacity model.

Recommendations

If you want a good SSD for your laptop:

  • Buy a 840 Pro or wait a little for the 850 Pro

If you want a quick access filing archive storage for your graphics worksets etc.

  • Buy 500GB or 1TB EVO. (...not as your only storage w/o backup, just a fast "other disk")

Don't use any desktop SSD for server. Don't buy an OEM server SSD from aftermarket without considering the risks.

  • If you have immediate need, get the Intel DC S3700 for more critical servers and 
  • once launched, look at putting the Samsung 845DC PRO / EVO in most places to boost everything.

There is a 845DC PRO review now - it's hard to believe but it is very very close to the DC S3700. Storagereview didn't "find" a steady state hole. I'm still looking for other reviews, as Anandtech did see one a one for the 850 Pro.

Notes

Terabytes Written (TBW) not listed                                                                                                       

If you use consumer SSD for other uses, we have nothing to talk. Good desktop SSDs will most probably outlast your desktops lifespan. Yet, TBW is all too often abused as an excuse for going with lower-spec-than-sensible SSDs. If you put them in a Ceph storage cluster instead of server models (with hardened firmware), then you're to blame and I don't wanna support this :)    

MB/s numbers

The only uncharacteristic performance numbers are for the two high-write models, the SSD823 (~200MB/s either way) and the SSD1625 that has between 740MB/s (w) and 848MB/s (r) thanks to dualport SAS. Note not every HBA or backplane allows to make use of dualport connects for more than redundancy.

All the other ones are somewhere along the lines of 500-550MB/s read and 350-500MB/s write. In practice, tuning your queue depths and readahead will matter more than that.

Help me fill missing values @FlorianHeigl1 on Twitter...                                               

IOPS might be "datasheet IOPS" only

Almost all models degrade in write performance after a prolonged write-heavy use without "breathing" room. The degradation seems to be between 30% and 90% depending on the model. Refer to the steady state column to see the more interesting long-term numbers. That's the performance you'd see under memory pressure and with TRIM issues (i.e. on OSX 10.9).

Right now only the SM823, SM1625 give good write IOPS in the long run, they're the only SSDs suitable for serious enterprise use. Yet, it fully makes sense to only use those in hotspot areas and not for the 95% of enterprise data that moves almost never.

The webserver-aimed PM843T also doesn't degrade, but at 2k there's also not much to degrade *from* - that's the performance a good raid hba gets out of a few 7.2k disks.