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Comment by barrkel | Hacker News Reader

I built my home system early this year using the Samsung 960 Evo 1TB M2. Actual speeds were nowhere near advertised speeds until I enabled write-back cache on the drive, which gave me pause for concern about data persistence reliability. AFAIK the Samsung drivers (as opposed to the MS drivers I originally used) just turn this on without needing to be twiddled in settings.

Just to confirm, I have seen the behaviour described herein, with write-back cached making enormous difference with the Samsung EVO product in particular.

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Microsoft's NVMe driver is generally regarded within the storage industry as a bad joke. The fact that it has very different cache control behavior from their SATA driver despite the two using the same check box and same help text is really inexcusable.

Watch the following video that explains why the 960 EVO has poor write performance after exhausting its cache:

https://youtu.be/RqaZTwW_X2o?t=511

For sustained write performance you need the 960 PRO.

I also have a Samsung 960 Evo. Its performance is what I consider a joke, fio and pg_test_fsync make it almost look as slow as spinning SAS drives.

For example on a 4kb sync write with 16 threads test, the 960 Evo cannot do more than 1000 iops. In comparison the Intel P4800X (Optane) does friggin 500 000 iops on the same test. That is a 500X difference.

https://forums.servethehome.com/index.php?threads/did-some-w...

The 960 EVO is a consumer grade SSD with firmware tuned for bursts of I/O (through eg. the use of SLC write caching) at the expense of sustained write throughput. It doesn't have power loss protection capacitors, so it can't perform safe write caching when you're issuing synchronous writes. 4kB is much smaller than the underlying page size of its NAND flash, so performance is going to suck without write combining. You're testing it in shackles, with a workload that doesn't at all match its intended use case. That doesn't make it a joke, it just makes it the wrong kind of drive to use for stereotypical enterprise applications.

So what is the use case for this drive? The 960 Evo/Pro are supposed to be premium models, but a better investment would be a cheaper SSD drive with more storage. And if you rarely write that much, more ram will increase the read speed significantly.

a consumer pc.

the pro does not have the buffer the evo does. the evo is not a premium model, it is entry level cutting edge

That is not very specific, a consumer PC would be fine with a 750 Evo also, maybe two of them in raid 0 for twice the sequential read & write speed. I believe for most consumers, having more SSD storage per $ is more important.

a 750 evo is a sata drive, a 950 is an nvme drive. completely different technology. if my laptop has an nvme slot why would i buy a sata drive. 2 750s is not faster than 1 950

It is nowhere near as slow as spinning drives, that's ludicrous. Mega IOPS are simply not required in a desktop. I'm not trying to run multiple VMs with multiple databases on this thing. In fact it's rarely writing at all.

Have you checked your SMART data for how much your read/write ratio is? I think you will find those results surprising, even when you think that you don't write that often.

It's not just a matter of how many bytes are being written; desktop workloads rarely need to do synchronous writes.

There are a lot of desktop applications that does synchronous all the time. Chrome, Firefox and Spotify are a few examples as they use SQLite which does fsync() system call. But yeah, you will be fine even with a spinning hard drive. My point is, what use case is there for paying a premium for the Samsung NVMe's when you would be just fine with a cheaper model.

The IO done by applications like web browsers and Spotify may be synchronous from their perspective (i.e. write(2) syscalls instead of aio), but those applications definitely don't need the sort of hard ACID transactional guarantees that require all disk caches to be disabled and every single write command sent to the drive to be a barrier. The fact that they're running atop journaling filesystems is good enough.

I've had about 20 spinning drives fail on me in the past 25 years or so. The more I can keep spinning drives out of my life, the happier I am, generally.

You're right about the volume of data written; it's nearly as much as read, likely due to continuously syncing browsers - I leave my desktop on 24/7, and run 2 browsers, all of which probably doesn't help. It doesn't add up to an argument for high IOPS though.

I chose the Samsung drive primarily because of all the stories about premature SSD failures - all the drives I've bought have either been Intel or Samsung. I got this model because it was the 1TB option that was both SSD and either Samsung or Intel.

I cannot tell you how many days I've wasted replacing disks in home raid arrays, or before that recovering data from backups. I'm also done with trying to shuffle data between tiny SSDs and large spinning disks based on required speed of access. I keep all my bulky files on my ZFS NAS, but I don't worry about how many apps or games I have installed - 1T has, for now, been more than enough.

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