4 ms·

Text is wrong about CRCs: everyone uses pretty heavy ECC, so it's not just a re-read. This also provides a somewhat graduated measure of the block's actual hea

by markhahn 10mo ago

Text is wrong about CRCs: everyone uses pretty heavy ECC, so it's not just a re-read. This also provides a somewhat graduated measure of the block's actual health, so the housekeeping firmware can decide whether to stop using the block (ie, move the content elsewhere). I'm also not a fan of buy bigger storage concept, or the conspiracy-theory on 480 v 512. It sure would be nice if when considering a product, you could just look at some claimed stats from the vendor about time-related degradation, firmware sparing policy, etc. we shouldn't have to guess!

saurik 10mo ago
> I'm also not a fan of buy bigger storage concept, or the conspiracy-theory on 480 v 512. I don't understand why this is being called a "conspiracy theory"; but, if you want some very concrete evidence that this is how they work, a paper was recently published that analyzed the behavior and endurance of various SSDs, and the data would be very difficult to describe using any other theory than that, comparing apples-to-apples on drives that have better write endurance, they are merely overprovisioned to allow the wear-level algorithm to not cause as much write amplification while reorganizing. https://news.ycombinator.com/item?id=44985619 https://news.ycombinator.com/item?id=44985619 > OP on write-intensive SSD. SSD vendors often offer two versions of SSDs with similar hardware specifications, where the lower-capacity model is typically marketed as “write-optimized” or “mixed-use”. One might expect that such write-optimized SSDs would demonstrate improved WAF characteristics due to specialized internal designs. To investigate this, we compared two Micron SSD models: the Micron 7450 PRO, designed for “read-intensive” workloads with a capacity of 960 GB, and the Micron 7450 MAX, intended for “mixed-use” workloads with a capacity of 800 GB. Both SSDs were tested under identical workloads and dataset sizes, as shown in Figure 7b. The WAF results for both models were identical and closely matched the results from the simulator. This suggests that these Micron SSDs, despite being marketed for different workloads, are essentially identical in performance, with the only difference being a larger OP on the “mixed-use” model. For these SSD models, there appear to be no other hardware or algorithmic improvements. As a result, users can achieve similar performance by manually reserving free space on the “read-intensive” SSD, offering a practical alternative to purchasing the “mixed-use” model.

saurik 10mo ago

> I'm also not a fan of buy bigger storage concept, or the conspiracy-theory on 480 v 512. I don't understand why this is being called a "conspiracy theory"; but, if you want some very concrete evidence that this is how they work, a paper was recently published that analyzed the behavior and endurance of various SSDs, and the data would be very difficult to describe using any other theory than that, comparing apples-to-apples on drives that have better write endurance, they are merely overprovisioned to allow the wear-level algorithm to not cause as much write amplification while reorganizing. https://news.ycombinator.com/item?id=44985619 https://news.ycombinator.com/item?id=44985619 > OP on write-intensive SSD. SSD vendors often offer two versions of SSDs with similar hardware specifications, where the lower-capacity model is typically marketed as “write-optimized” or “mixed-use”. One might expect that such write-optimized SSDs would demonstrate improved WAF characteristics due to specialized internal designs. To investigate this, we compared two Micron SSD models: the Micron 7450 PRO, designed for “read-intensive” workloads with a capacity of 960 GB, and the Micron 7450 MAX, intended for “mixed-use” workloads with a capacity of 800 GB. Both SSDs were tested under identical workloads and dataset sizes, as shown in Figure 7b. The WAF results for both models were identical and closely matched the results from the simulator. This suggests that these Micron SSDs, despite being marketed for different workloads, are essentially identical in performance, with the only difference being a larger OP on the “mixed-use” model. For these SSD models, there appear to be no other hardware or algorithmic improvements. As a result, users can achieve similar performance by manually reserving free space on the “read-intensive” SSD, offering a practical alternative to purchasing the “mixed-use” model.