Original URL: https://www.theregister.com/2014/08/11/review_samsung_845dc_evo_and_845dc_pro_ssd_storage/

On test: Samsung 845DC EVO 3-bit Toggle MLC and 845DC PRO 3D V-NAND SSDs

Designer storage for enterprise and data centre

By Simon Crisp

Posted in Storage, 11th August 2014 09:05 GMT

Review The push of SSDs into areas once considered the domain of the standard hard drive storage shows no appetite in slowing down, in fact the estimate is that the SSD market will grow by 30 percent this year (2014) alone.

Samsung SSD845DC EVO

Samsung SSD845DC EVO or PRO? You can't tell from the top but inside they are different beasts

Many of these drives will end up in data centres and other enterprise storage areas, and Samsung has released a couple of new drive ranges targeted at these segments: the SSD845DC EVO and the brand new SSD 845DC PRO.

In the past, Samsung drives aimed at this market segment have been pretty much OEM only but with the DC range it seems it has relented on this policy. The drives are available to SMB users and anyone else who fancies them. Although Samsung claims both SSDs offer best-in-class sustained performance, internally they are quite different beasts.

Samsung 845DC EVO (480GB)

Aimed at read-centric applications such as content delivery networks and web servers the Samsung 845DC EVO uses 19nm 3-bit Toggle MLC (multi-level cell) NAND, the first drive in this segment to do so. Indeed, this is an interesting stance taken by Samsung over TLC (Triple Level Cell) NAND.

Samsung SSD845DC EVO

Samsung SSD845DC EVO

When it was introduced in the SSD840, the general opinion (outside the company that is) was that TLC NAND was a dodgy road to go down given its higher latency and lower endurance than MLC. If you want to knock that assumption on the head, there’s no better way than sticking the NAND in a drive aimed at one of the most demanding of environments for storage drives – the data centre.

Samsung SSD845DC EVO PCB top

Samsung SSD845DC EVO PCB top

Coming in 240GB, 480GB and 960GB capacities, the 240GB and 480GB drives have 512MB of LPDDR2 cache while the 960GB uses 1GB. The 845DC EVO uses the Samsung MEX S4LN045X01-803, 400MHz, 8-channel MEX controller that first saw the light of day in the SSD850 EVO consumer drive. However, the firmware has been written with data centres in mind, providing end-to-end data protection and error correction through advanced signal processing with thermal protection support added into the mix.

To get to its 480GB capacity, the drive uses just four 128GB NAND chips, each chip having eight 16GB dies. Sitting on one side of the PCB – along with the controller and cache chip – are twenty three tantalum capacitors in multiple rows, which allows the drive to write all the data in the cache to the NAND, in case of power failure.

Samsung SSD845DC EVO PCB bottom

Samsung SSD845DC EVO PCB bottom

All three drives in the range have quoted sequential read performance of up to 530MB/s with both the 480GB and 960GB models having a write performance of up to 410MB/s while the 240GB drive lags behind writing at up to 270MB/s.

Samsung 845DC PRO (400GB)

While the 845DC EVO is aimed at read-centric applications, the SSD845DC PRO is aimed at write-centric ones such as app and database servers and uses the 24-layer version of the company’s new 40nm 2-bit 3D – Vertical NAND stacked cell technology, another Samsung world first.

Samsung SSD845DC PRO

Samsung SSD845DC PRO

The one thing that the new design of NAND gives the 845DC PRO is endurance, helped in no small part by its larger geometry. Samsung claims the drive can perform 10 Drive writes Per Day (DWPD) which works out at a colossal 4TB per day or 7,300TB TBW (Total Bytes Written) for the 400GB model over the length of its five year warranty period. To give you an idea of how much of an improvement that is over the 845DC EVO, the 480GB EVO has a TBW of just 300.

As it stands the 845DC Pro comes in only two flavours; 400GB and 800GB with the 400GB unit having 512MB of DDR2 cache which is doubled for the 800GB drive. To reach its 400GB capacity the drive uses four 128GB Samsung K9PKGY8S7M-CCK0 3D V-NAND chips which gives a total of 512GB, so that means there is 27 per cent over-provisioning provided, much more than its consumer cousins.

Samsung SSD845DC PRO PCB top

Samsung SSD845DC PRO PCB top

Looking after this drive is, somewhat surprisingly, an older controller in the shape of Samsung’s 300MHz MDX S4LN021X01-8030 chip. It’s the controller that was launched with the SSD840 PRO but with completely re-written firmware to take account of its data centre requirements and control of the new NAND technology.

An interesting point with the design of the PCB is that Samsung is only using one side of it to hold the controller, NAND and cache. The other side of the board is home to the tantalum capacitors which, just like 845DC EVO, allows the drive to write all the data in the cache to the NAND in case of a power outage.

Samsung SSD845DC PRO PCB bottom

Samsung SSD845DC PRO PCB bottom

Quoted sequential read performance for the 845DC PRO is the same as the 845DC EVO i.e. up to 530MB/s but the new NAND gives the PRO significantly better write performance at up to 460MB/s for both capacities of the drive.

Performance

When tested with the ATTO benchmark, the 480GB 845DC EVO produced sequential read/write figures that were both higher than the officially quoted figures – 556MB/s for reads and 438MB/s for writes. It’s the same story for the 400GB 845DC Pro, the ATTO benchmark giving up a read score of 563MB/s and 485MB/s for writes, both figures comfortably faster than the official figures.

Samsung SSD845DC EVO CrystalDiskMark results

845DC EVO CrystalDiskMark results: single drive, RAID 0 and RAID 1
Click for a larger image

Samsung SSD845DC EVO ATTO results

845DC EVO ATTO results: single drive, RAID 0 and RAID 1
Click for a larger image

Samsung SSD845DC EVO AS SSD results

845DC EVO AS SSD results: single drive, RAID 0 and RAID 1
Click for a larger image

The 3D V-NAND in the 845DC PRO gives it better sequential read and more significantly a superior write speed performance compared to the EVO. I also did some real life testing – copying a 50GB folder (containing 28,523 files), a 4GB image and a 17GB Blu-Ray image. Using the Teracopy app I was able to get a MB/s figure as well as a time taken for the copying to complete.

As Samsung gave me two drives of each type to play with, it seemed impolite not to set them in a couple of RAID arrays so I set them into RAID 0 and RAID 1 setups to see how they perform. As you might expect in RAID 0, both paired drives have significantly faster sequential read/write speeds.

In the ATTO benchmark the RAID 0 EVO’s gave read/write scores of 1094MB/s and 832MB/s while the PRO is even faster, producing 1113MB/s for reads and 947MB/s for writes.

Samsung SSD845DC PRO CrystalDiskMark results

845DC PRO CrystalDiskMark results: single drive, RAID 0 and RAID 1
Click for a larger image

Samsung SSD845DC PRO ATTO results

845DC PRO ATTO results: single drive, RAID 0 and RAID 1
Click for a larger image

Samsung SSD845DC PRO AS SSD results

845DC PRO AS SSD results: single drive, RAID 0 and RAID 1
Click for a larger image

For the 50GB folder copy, the PRO and EVO single drive figures were 9min 05s and 9min 09s respectively. The only marked difference was 2min 06s (PRO) and 2min 25s (EVO) for the 17GB Blu-ray copy. The 4GB image copy was identical at 32s. As for the RAID results, the 845DC PRO had the edge on the EVO, being around 10 to 15 per cent faster.

The Reg Verdict

Both of these new Samsung drives bring new technologies to the enterprise/data centre market but only time will if either gains acceptance in this segment, especially the 3D V-NAND. This has the potential to bring huge capacity drives with endurance to match and that’s the key in this market segment. Just how good those Samsung endurance figures pan out in real life for the 845DC PRO remains to be seen. ®