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by flogic 4431 days ago
The first hit for "SSD write speeds" says ~500Mb/s (I hope I got the right b). I didn't bother clicking the links that just the blurb under it. He's dumping 128Mb in ~200 ms. I'm not sure there is much room for improvement.
3 comments

MB. Bytes. nobody quotes disk speeds in bits (or if they do I typically ignore them).

I've frequently observed sustained 500MB/sec writes and reads on my cheap ($250) 250GB SSDs. One of my favorite instances was running out of RAM while assembling a gigapan in Hugin. I added a swap file on my SSD and continued- it ran over night with nearly 500MB/sec reads and writes more or less continuously, but the job finished fine.

I weep for the memory sectors that got re-written continuously for an entire night.
If the controller on the SSD was working properly those writes were distributed evenly over the flash.
I used to, but given not a single one of my SSD drives (I have 4 deployed in my house) has so much as balked once in a year of continuous deployment, I am cautiously optimistic.
I've had very good reliability from my SSD drives as well. Some have been running almost continuously since 2009.
I ran a 60GB SSD as my Windows machine's system drive (with pagefile) for four years before it started showing problems, and that machine saw a few hours use almost every day. It was >90-95% full for most of that time.
SSD controllers do write-leveling, the blocks a filesystem writes to is virtual and remapped (think VMEM)
wouldn't an ~8GB page/swap file being continuously rewritten on a 250GB drive still consume a non-negligible number of write cycles over several days / weeks at most?
It depends on how much free space you have on the SSD. But yes, especially because the swap file isn't ssd-aware, you get a high degree of write amplification which wears the disk more than necessary. That being said, newish SSDs can take a beating, even under these kinds of workloads.
I think swap files are written page-wise, so as long as the start of the page file is aligned, all the writes should be aligned. (assuming memory page size and SSD page size are the same)
BTW I already have 16GB RAM on the machine. The swap file was 32GB.
Depends on the SSD. The PCIe SSD in a 2013 Retina MBP can approach 1GB/sec, and of course high-end PCIe server stuff can do better again; you may also have a striped RAID setup.
> The first hit for "SSD write speeds" says ~500Mb/s (I hope I got the right b).

Nope, it's MB not Mb.