But because it's still a black box which pretends to be a 16GiB 'disk', they don't see the need to change the model number. So that's nice for them. Random write performance is also poor, since the chance of hitting a block containing data is high.
But the problem for everyone else is that you don't actually know about the internals of one of these devices. For SLC, partial page writes are allowed, up to 4. You have no idea how a given FTL will handle sequential vs. It's a shame that TRIM is such a performance problem in many current implementations Is it somehow a hybrid of log-structured and in-place-modified FS.
In contrast, eMMC abstracts many details away from us and our processor so we don't have to deal quite so directly with them nor take the performance hit.
Raw NAND changes a lot requiring near constant requalifying of parts as vendors change their manufacturing processes. What we've heard is: Once the blocks are all written once, garbage collection will begin and the performance will be gated by the speed and efficiency of that process.
But this layer is extremely leaky.
Also, even if the physical disk is damaged at one location, such that a certain sector is unreadable, the disk may be able to use spare space to replace the bad area, so that the sector can be overwritten. One of its operations, deallocate performs trim. It was measuring several key device health parameters and evaluating them within the drive firmware.
These may include increased heat output, increased noise level, problems with reading and writing of data, or an increase in the number of damaged disk sectors.
What we don't have a solid handle on is what exactly that will require of us. The fact that flash erase block are much higher than write blocks is central feature of flash and it can not be ever fully hidden. Unless you have a particularly recalcitrant ODM, you should at least get some notice of that kind of thing rather than finding it out post-build-run.
Back to F2FS, What you are saying is that: Maybe there are some well known limitations to the FTL found in the typical SD card, but I don't know them, so it is not clear to me how F2FS happens to be Nand friendly, when precisely the nand characteristic are carefully hidden by the SD card embedded controller.
There are 2 basic mapping schemes and many variants of such. TRIM can take a lot of time to complete, depending on the firmware in the SSD, and may even trigger a garbage collection cycle.
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S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology; often written as SMART) is a monitoring system included in computer hard disk drives (HDDs), solid-state drives (SSDs), and eMMC drives.
Its primary function is to detect and report various indicators of drive reliability with the intent of anticipating imminent hardware failures. As with SD cards, not all eMMC storage is created equal—some eMMC storage is slower than others.
However, all eMMC storage will be slower than a proper SSD. When comparing performance, you’ll probably want to look up storage benchmarks for the eMMC-based device in question—some devices are faster than others.
Datalight’s FlashFXe software accelerator for eMMC, which integrates seamlessly with the Reliance Nitro fault-tolerant system on Linux and Android, significantly reduces write amplification that.
•SSD = Solid State Drive Write Amplification Factor Bytes written to NAND versus bytes written from PC/Server Controller (FTL) Wear Leveling Over-provisioning Garbage Collection Host Application Write Profile (Ran vs.
Seq) Free user space / TRIM Bytes written to NAND.Emmc write amplification