Plextor PX-256M5S full review

Shinano Kenshi, better known in this country by the name Plextor, is steadly building an extensive range of solid-state drives for upgrading desktop PCs and laptops. 

Read more solid-state drive reviews.

We have previously reviewed the Plextor PX-256M2S, a high-performance SATA 6Gbps SSD when it launched, even if its circa-430MBps speed has now been surpassed by more recent SSDs.

The Plextor M5S, available in 64GB, 128GB and 256GB capacities, also takes a Marvell controller chip to ensure stable consistent performance with all data types. This is in contrast with, for example, SandForce-based designs which use data compression to improve write performance against only limited types of data.

Plextor leverages its advantage here by marketing its SSD products with the True Speed label, indicating its use of consistent and accurate specifications, rather than artificially high benchmark results.

For best performance, Plextor now has its M3 and M3 Pro models leading the way; the Plextor M5S range meanwhile is based on the former but made available at a lower price.

One of the challenges of SSD design is not just to make a drive speedy out of the box, but to maintain high performance as the drive is used. To this end, Plextor tells us it has exclusive innovative firmware running on the Marvell 88SS9174-BLD2 chip. ‘Instant Restore’ is technology to rearrange data blocks, handle garbage collection and optimise unused space.

At the production stage, Plextor’s quality-control process burns-in the drive for 20 hours at high temperature, to simulate real working conditions. The annual failure rate (AFR) of 0.5% is said by Plextor to be the lowest in the industry.

The Plextor PX-256M5S SSD comes in a lightweight metal shell, with wraparound brushed aluminium top and similar baseplate. Its interface is the current-fastest SATA 6Gbps type, otherwise known as ‘SATA 3’ and this model of SSD includes a generous 512MB of memory cache. 

Unlike the dearer M3 and M3 Pro which use toggle NAND flash for storage, the M5S has 25nm Micron ONFi chips. 

Our sample was boxed as just a drive, with no accessory kit for 3.5in mounting, USB-SATA cable or USB drive caddy.

Plextor PX-256M5S: Performance

Plextor’s own benchmarks peg the M5S at over 500MBps reads and over 400MBps writes. In our tests, we found the M5S often exceeding indicated performance, with the ATTO test (which normally gives best-case results) reaching 538 and 403 MBps, for reads and writes respectively. 

The CrystalDiskMark confirmed the SSD’s near indifference to data type, here scoring up to 502/402 MBps for sequential read/writes, and maintaining good speeds for small 512kB transfers, at 372 and 387 MBps respectively.

In the 4kB QD32 test with multiple small-file streams, the M5S also recorded decent read and write results of 306 and 280 MBps.

We measured input/output per second (IOPS) using the AS SSD benchmark tool. The Plextor here matched the advertised 73,000, scoring 73,714 for 4kB reads with 64 threads; and write performance was close to published 70,000 speed, showing 64,462 IOPS.

The overall nominal score shown by AS SSD was 911 points, an outstanding result and the highest we’ve ever recorded in the lab. The highest numbers we've hitherto seen here were for the Corsair Performance Pro 256GB, which hit 871 points.

Finally, the HD Tune Pro test resulted in a near-ruler flat plot for both read and write tests, a sign of consistent performance across the drive under load. Reads here averaged 517 MBps and writes 381 MBps.


Plextor PX-256M5S: Specs

  • 256GB solid-state drive
  • 2.5in SATA 6Gbps
  • also available in 64GB, 128GB capacities
  • Marvel 88SS9174-BLD2
  • Plextor firmware 1.0
  • Micron ONFi NAND flash
  • MTBP = 1.5m hours
  • 100 x 69.85 x 9.5mm
  • 61g
  • 3-year warranty

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