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Seven 2.5-inch mobile drives compared


Solid-state flash takes on the mechanical monarchy
— 10:41 PM on July 14, 2008

It's a rare thing in this industry to be potentially on the verge of a paradigm shift, as a stream of consistent, impressive, but nonetheless incremental upgrades to a given technology runs out of road and is overtaken by an entirely new way of doing things. Such will one day be the case with electric and hybrid motors supplanting internal combustion engines in cars. Maybe. Right after they start to fly.

Some would argue that we're on the brink of a dramatic shift in the storage world. Mechanical hard drives that store data on platters spinning at thousands of revolutions per minute have reigned here for decades, and today's finest are technical marvels of microscopic mechanics. But can they stand up to flash-based solid-state drives riding the tidal wave that is Moore's Law?

Solid-state drives have recently become more prominent on the mobile front, where their low power consumption and robust shock tolerance are clear advantages over the mechanical monarchy. Densities are up and prices are falling, too, allowing for budget models that won't have you pondering auctioning off a kidney. The latest mechanical mobile drives are hardly dinosaurs, though. Perpendicular recording has done wonders, enabling the latest 2.5" disks to spin an impressive 320GB at 7,200 RPM, with 16MB of cache riding shotgun—that was a well-equipped 3.5" desktop drive a couple of years ago.

The obvious questions, then, are how these two competing storage technologies stack up and which is right for you. In search of answers, we've rounded up seven 2.5" mobile drives, including SSDs from OCZ, Samsung, and Super Talent, and traditional mechanical drives from Seagate and Western Digital. Read on for the enlightening results of this battle between machines and memory.


Meet the new boss?
Unlike mechanical hard drives, solid-state offerings store data on flash memory chips—the same sort of silicon you'll find inside USB thumb drives, only much faster. In SSDs, multiple chips are tied together by a controller, which drive manufacturer Super Talent says is actually the biggest determinant of overall performance.

The solid-state approach has numerous benefits, perhaps the most striking of which is a near-instantaneous seek time. Memory chips don't have to overcome the rotational and mechanical latency associated with spinning platters and drive head movement, so they aren't easily flummoxed by random access patterns. A lack of moving parts also makes solid-state drives nearly impervious to physical shock and vibration, in addition to allowing them to operate in complete silence. And let's not forget that memory chips require much less juice than do spinning platters, which gives solid-state drives an edge in the power consumption department.

So far, solid-state drives sound pretty sweet, but there are some drawbacks. Capacity and price are huge constraints, conspiring to give SSDs a much higher cost per gigabyte than traditional hard drives.


The life expectancy of flash storage has been a major concern, as well. Flash memory cells can withstand an unlimited number of read operations, but there's a ceiling on the number of write or erase ops they can tolerate. Multi-level cell (MLC) NAND flash stores two bits per cell and is good for 10,000 write-erase cycles. This memory type is often used in budget SSDs, and you'll find it in the Super Talent MasterDrive MX we're testing today. Single-level cell (SLC) flash stores only a single bit per cell, and its tolerance for write-erase ops grows by an order of magnitude to 100,000 cycles. SLC memory is found in the OCZ and Samsung drives in this round-up.

Of course, the number of write-erase cycles isn't exactly a clear indicator of a drive's lifespan. Super Talent has come up with its own endurance spec that makes better sense of the numbers. This spec estimates drive lifespan based on 50GB of write-erase ops per day, which for the 60GB MasterDrive MX results in an expected lifespan of just under 33 years. Thanks to their use of SLC memory and slightly higher storage capacities, the OCZ and Samsung SSDs should last over 350 years with 50GB of write-erase ops per day. For most applications, then, longevity shouldn't be an issue, even for MLC drives.

In fact, solid-state drive makers claim their drives are more reliable than mechanical counterparts thanks to the absence of moving parts. All three of the SSDs we're looking at today have a Mean Time Between Failures (MTBF) rating of at least a million hours, and the Samsung and OCZ drives are rated for up to two million hours. However, despite this apparent enthusiasm for longevity, SSD warranty coverage is a little lacking. You only get a single-year warranty with each of the drives we're looking at today, which looks pretty stingy next to the three-year warranties that are standard with most notebook drives, not to mention the five years of coverage you get with Seagate drives and premium models from other manufacturers.

In all fairness, we should note that not every SSD is plagued by a short warranty. Super Talent has SLC-based drives that come with three-year warranties, and OCZ just announced a line of budget "Core" drives that will be covered for two years. OCZ says its 64GB Core drive will sell for only $259, but it's not available just yet.

OCZ SATA II Samsung FlashSSD Super Talent MasterDrive MX
Maximum external transfer rate 300MB/s 300MB/s 300MB/s
Maximum sequential read rate 100MB/s 100MB/s 120MB/s
Maximum sequential write rate 80MB/s 80MB/s 40MB/s
Average seek time 0.1ms 0.1ms 0.1ms
Capacity 64GB 64GB 60GB
Idle power 0.32W 0.32W NA
Read/write power 0.41W 0.41W NA
Mean Time Between Failures (MTBF) 2,000,000 hours 2,000,000 hours 1,000,000+ hours
Warranty length One year One year One year
Street price

We don't yet know which manufacturer will be behind the Core line, but if our pictures haven't already made it clear, the OCZ SATA II is essentially identical to the Samsung FlashSSD. OCZ hasn't done anything to tweak the memory chips or controller, despite its expertise in the field, which makes the SATA II's $100 price premium over the FlashSSD a little curious. The OCZ drive does come with a $100 mail-in rebate, if you feel like rolling the dice and waiting a couple of months to make up the difference.

Of course, both the Samsung and OCZ drives cost significantly more than the Super Talent. But they have a better balance of read and write speeds, offering 100MB/s for the former and 80MB/s for the latter. The MasterDrive is heavily biased toward read performance, where it can apparently manage up to 120MB/s. Writes, however, top out at just 40MB/s. For what it's worth, Super Talent says it has a new firmware revision for the MasterDrive that doubles write speeds. Users can't, er, flash drives with the new firmware themselves, but if you send your MasterDrive to Super Talent, they'll do it for you. This new firmware is apparently shipping on all new MasterDrives, as well.

While we're talking about the MasterDrive, it's interesting to note that it offers only 60GB of storage capacity rather than the industry standard 64GB. Super Talent says that SSD makers often overstate the capacity of their drives, failing to account for unusable portions reserved for wear leveling and bad bit management. When formatted in Windows XP, the MasterDrive 60GB yields 60,463,996,928 bytes, or 56.3GB. However, the OCZ and Samsung 64GB drives format to 64,017,317,888 bytes, or 59.6GB. So the MasterDrive's usable capacity is a little lower, then.