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WD SN850 delivers the best performing SSD we've tested

tweaktown.com

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Re: WD SN850 delivers the best performing SSD we've tested

#41

Post by sushshshsh »

duskwuff wrote: post #32
gruez wrote: post #19

Earlier quoted context omitted.

>It is offloaded to tape at some point and restored periodically. This makes no sense. The main problem with disabling write flushing is what happens if the OS crashes or the power goes out. Doing periodic backups/restores provides a "last known good state" to revert to, but you'll still lose all the writes between the last backup and when you crashed. Depending on your workload this might be fine, but I doubt the CO…

Explicitly rewriting data periodically might make sense if you're really paranoid about flash fading over time. But bouncing the data through tape (tape!!) still makes no sense; the sensible way of managing this would be to mirror the data directly to another SSD.

We are arguing about nothing. Live data (being accessed many times per day) stays on SSDs. The middle tier of data is a gray area and can go on SSDs or disk.

But if you think that your FB or Youtube or Fidelity or Geico or SSN or IRS or Apple or Google data isn't sitting on a tape somewhere, you are extremely mistaken, because I was the one who wrote the tape control software they purchased from us.

Re: WD SN850 delivers the best performing SSD we've tested

#43

Post by rasz »

faster wrote: post #11

Maybe I haven't been paying attention, but I've never had a site attach extra text to copied text like this site does. I wanted to see what the test machine's case looks like, so I copied the make and model and pasted it into a search bar, and got "Read more:" and a link to the page along with the text I wanted to copy. No thanks. I'll be skipping that site in the future, unless that javascript comes from a place I c…

    document.addEventListener('copy', (event)=>{
        const pagelink = `\n\nRead more: ${document.location.href}`;
        event.clipboardData.setData('text', document.getSelection() + pagelink);
        event.preventDefault();
    })
To prevent this make a custom extension

     "run_at": "document_start"
and inject

    window.addEventListener('copy', e => e.stopImmediatePropagation(), true);
alternatively use for example https://www.tampermonkey.net with

    Experimental Inject Mode: Instant
to inject your pacifying script.

Re: WD SN850 delivers the best performing SSD we've tested

#44

Post by [deleted] »

sushshshsh wrote: post #10
vegardx wrote: post #8

Earlier quoted context omitted.

Uhm, what? There are tons of ways to prevent data loss, none of them involves writing the data out to tapes and then back in again.

Sure, you can also write to disk or other media. But are you trying to argue that certain large companies don't use tape?

[deleted]

Re: WD SN850 delivers the best performing SSD we've tested

#45

Post by fomine3 »

wtallis wrote: post #30
pizza234 wrote: post #4

Earlier quoted context omitted.

StackOverflow answer here: https://superuser.com/a/1215634 It's essentially the typical "without this enabled, you will lose data in case of power loss, potentially breaking the O/S".

One important point that the StackOverflow answers miss is that the Windows checkbox for buffer flushing has a different meaning for SATA SSDs than for NVMe SSDs. If you want a reasonably fair synthetic benchmark to compare NVMe SSDs against SATA SSDs while bypassing any caching the OS is doing with main system RAM, you pretty much have to toggle that switch for at least NVMe drives. Or use Linux, which has actual do…

I assume you're Billy Tallis on AnandTech, so you set disabled the cache on test?

Re: WD SN850 delivers the best performing SSD we've tested

#47

Post by wtallis »

gruez wrote: post #39
wtallis wrote: post #30

Earlier quoted context omitted.

One important point that the StackOverflow answers miss is that the Windows checkbox for buffer flushing has a different meaning for SATA SSDs than for NVMe SSDs. If you want a reasonably fair synthetic benchmark to compare NVMe SSDs against SATA SSDs while bypassing any caching the OS is doing with main system RAM, you pretty much have to toggle that switch for at least NVMe drives. Or use Linux, which has actual do…

>One important point that the StackOverflow answers miss is that the Windows checkbox for buffer flushing has a different meaning for SATA SSDs than for NVMe SSDs. can you elaborate on this? What's the exact difference? Do sata drives get more aggressive buffer flushing than nvme drives?

The exact difference, as far as I'm aware, has never been publicly documented by Microsoft, and I have not attempted to properly and thoroughly reverse engineer that particular mess.

But the end result is that in the default state (buffer flushing enabled), most or all disk benchmarking tools show drastically lower write performance on consumer NVMe drives than should be expected compared to their theoretical advantage over SATA SSDs.

I'm not intimately familiar with the semantics of how flush/sync commands get generated and passed through the Windows IO stack. Empirically, when an application tries to issue a write that is not to be buffered by the OS, it appears that Windows translates that into NVMe commands that constrain or entirely prohibit the SSD from doing its own write buffering, but for SATA SSDs writes are still by default issued in a manner that permits the drive to buffer freely. Figuring out exactly what's happening without Microsoft's help might require bus analyzers I don't have. In effect, it seems that Windows is less willing to trust a NVMe SSD than a SATA SSD, and that doesn't strike me as justified.

I've also noticed that recent builds of Windows 10 have changed their behavior when running one of our old benchmarking tools that plays back IO traces. On current Windows 10, the OS outright rejects any attempt by the trace playback application to issue a flush command to a NVMe SSD, whether or not buffer flushing is enabled at the driver level. This is definitely a change from earlier builds of Windows 10, and I think it is a change that only affects NVMe drives, not SATA drives. (I'm not testing very many SATA drives these days, and have to design my testing procedures entirely around the needs of testing NVMe drives.)

Re: WD SN850 delivers the best performing SSD we've tested

#48

Post by wtallis »

fomine3 wrote: post #45
wtallis wrote: post #30

Earlier quoted context omitted.

One important point that the StackOverflow answers miss is that the Windows checkbox for buffer flushing has a different meaning for SATA SSDs than for NVMe SSDs. If you want a reasonably fair synthetic benchmark to compare NVMe SSDs against SATA SSDs while bypassing any caching the OS is doing with main system RAM, you pretty much have to toggle that switch for at least NVMe drives. Or use Linux, which has actual do…

I assume you're Billy Tallis on AnandTech, so you set disabled the cache on test?

Whenever possible, I run synthetic tests on Linux to avoid this and many other frustrations. When running application tests on Windows, I leave the setting at its default: disk cache enabled, and buffer flushing allowed. When running synthetic benchmarks on Windows, I turn buffer flushing off to get an accurate measurement of the drive's capabilities, relatively unhindered by OS shenanigans.

Re: WD SN850 delivers the best performing SSD we've tested

#49

Post by wtallis »

sushshshsh wrote: post #41
duskwuff wrote: post #32

Earlier quoted context omitted.

Explicitly rewriting data periodically might make sense if you're really paranoid about flash fading over time. But bouncing the data through tape (tape!!) still makes no sense; the sensible way of managing this would be to mirror the data directly to another SSD.

We are arguing about nothing. Live data (being accessed many times per day) stays on SSDs. The middle tier of data is a gray area and can go on SSDs or disk. But if you think that your FB or Youtube or Fidelity or Geico or SSN or IRS or Apple or Google data isn't sitting on a tape somewhere, you are extremely mistaken, because I was the one who wrote the tape control software they purchased from us.

Nobody's denying that the data makes it to tape eventually. What everyone finds hard to believe is your assertion that data is ever moved from tape back into warm storage during the ordinary course of business. Enterprises use tape for backup. They only read data off tapes after something goes very wrong, or periodically to verify that their backup process is actually working. But except after a catastrophe, data read from tape is not routinely used to re-populate warm storage.

Re: WD SN850 delivers the best performing SSD we've tested

#50

Post by wtallis »

2Gkashmiri wrote: post #46

Can..... this be used as a media hosting drive? Like for plex and maybe heavy server loads?

This is complete overkill for anything resembling consumer NAS duty. It's far faster than any consumer-oriented networking equipment, and far more costly per byte than the cheapest consumer SSDs that still outperform your network. A drive like this is best suited for a workstation where large quantities of data are generated or processed locally.
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