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New PCIe SSDs Load Games, Apps As Fast As Old SATA Drives
crookedvulture writes Slashdot has covered a bunch of new PCI Express SSDs over the past month, and for good reason. The latest crop offers much higher sequential and random I/O rates than predecessors based on old-school Serial ATA interfaces. They're also compatible with new protocols, like NVM Express, which reduce overhead and improve scaling under demanding loads. As one might expect, these new PCIe drives destroy the competition in targeted benchmarks, hitting top speeds several times faster than even the best SATA SSDs can muster. The thing is, PCIe SSDs don't load games or common application data any faster than current incumbents—or even consumer-grade SSDs from five years ago. That's very different from the initial transition from mechanical to solid-state storage, where load times improved noticeably for just about everything. Servers and workstations can no doubt take advantage of the extra oomph that PCIe SSDs provide, but desktop users may struggle to find scenarios where PCIe SSDs offer palpable performance improvements over even budget-oriented SATA drives.
I mean, why would anyone think images would load faster? The cpu is doing enough transformative work processing the image for display that the storage system only has to be able to keep ahead of it... which it can do trivially at 600 MBytes/sec if the data is not otherwise cached.
Did the author think that the OS wouldn't request the data from storage until the program actually asked for it? Of course the OS is doing read-ahead.
And programs aren't going to load much faster either, dynamic linking overhead puts a cap on it and the program is going to be cached in ram indefinitely after the first load anyway.
These PCIe SSDs are useful only in a few special mostly server-oriented cases. That said, it doesn't actually cost any more to have a direct PCIe interface verses a SATA interface so I these things are here to stay. Personally though I prefer the far more portable SATA SSDs.
-Matt
The PCIe devices are faster; but (since they also tend to be either substantially similar to SATA devices; but packaged for the convenience of OEMs who want to go all M.2 on certain designs and clean up the mini-PCIe/SATA-using-mini-PCIe's-pinout-for-some-horrible-reason/mini-SATA/SATA mess that crops up in laptops and very small form factor systems; or tend to be markedly more expensive enterprise oriented devices that focus on IOPS) it isn't clear why you'd expect much improvement on application loading workloads.
SSDs are at their best, and the difference between good and merely adequate SSDs most noticeable, under brutal random I/O loads, the heavier the better. Those are what make mechanical disks entirely obsolete, cheap SSD controllers start to drop the ball, and more expensive ones really shine. Since application makers generally still have to assume that many of their customers are running HDDs(plus the console ports that may only be able to assume an optical disk and a tiny amount of RAM, and the mobile apps that need to work with cheap and mediocre eMMC flash), they would do well to avoid that sort of load.
HDD vs. SSD was a pretty dramatic jump because even the best HDDs absolutely crater if forced to seek(whether by fragmentation or by two or more programs both trying to access the same disk); but there aren't a whole lot of desktop workloads where 'excellent at obnoxiously seeky workloads' vs. 'damned heroic at obnoxiously seeky workloads' makes a terribly noticeable difference. Plus, a lot of desktop workloads still involve fairly small amounts of data, so a decent chunk of RAM is both helpful and economically viable. Part of the appeal of crazy-fast SSDs is that the cost rather less per GB than RAM does, while not being too much worse, which allows you to attack problems large enough that the RAM you really want is either heroically expensive or just not for sale. On the desktop, a fair few programs in common use are still 32 bit, and much less demanding.
When it's a second disc with a copy of files from the first disk, or a raid-0 mirror disk.
And that is sooo wrong. RAID 0 is not a mirror of any kind.
Raid 1 - data is mirrored across multiple drives
RAIND 0 - data is striped across multiple drives.