Niall’s virtual diary archives – Monday 14th December 2015

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Monday 14th December 2015: 2.23pm. Link shared:

Last Black Friday Amazon UK showed me a timed deal for a 240Gb Sandisk SSD Plus for £39, and very unlike me I did an impulse purchase. Unlike any of the other Sandisk SSDs but like the other ultra-budget SSDs on the market, this one has very little information on the web about it, no benchmarks, no idea what controller or flash, nothing.

So how bad is it? :) Well, with some effort I discovered it uses the castrated Silicon Motion SM2246XT controller with 19nm Sandisk MLC flash, and once you know that you'll find that a large chunk of the recent ultra-budget SSDs are also on the same controller, and are therefore essentially identically performing if they are also on MLC not TLC flash. The SM2246XT achieves its low cost by not having any dedicated DRAM cache for the flash mapping tables which also saves on having any capacitor to flush the tables on sudden power loss. As one might expect, that makes for poor i/o performance as you're always having to load tables from the flash for every new i/o.

Now, that just said, I benchmarked it against the four year old legendary Samsung 830 which never dies and against that it is quite competitive. Both have 20% of the single threaded random i/o performance of the latest SSDs, and both pretty much max out SATA 3 for sequential transfers. I'm sure the 830 with its 256Kb of DRAM flash table cache will perform much better where the SSD has cached where you'll access next, but then the 830 cost many times what the Sandisk SSD Plus did and was in its time a premium drive.

Assuming the Silicon Motion controller is reliable (and so far it appears to be), this ultra-budget SSD looks sound. Lucky, for an impulse buy.

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