HDD/SSD Performance With MDADM RAID, BCache On Linux 4.14

[uentity]

I think it would be interesting to test one more option of having external EXT4 journal on SSD. And how it performs with various journal size.

[Think]

If there is sufficient interest I will repeat the tests with XFS and (native RAID) Btrfs in a future article.

Talking about comparisons, ZFS would be interesting as well.

[duby229]

Well, in a lot of those benches bcache's writeback mode was actually slower than the single HDD. It seems weird.

[boxie]

The graph clearly shows BCache provides a significant performance improvement over HDD alone

and some others too. surely though it should be more performant (with the caveat that I know nothing about how it is implemented)

[torsionbar28]

I found this a rather odd statement, from the first graph:

"Using the BCache writeback mode where data is written to the SSD and then asynchronously to the HDD still leaves a significant performance drop compared to using a single SATA 3.0 SSD."

The graph clearly shows BCache provides a significant performance improvement over HDD alone, at least in this one test. Which is exactly what the mission of BCache is. Yes an SSD cache in front of an HDD is always going to be slower than a pure SSD storage environment - obvious statement is obvious. The point is it gives a nice performance boost to a mechanical HDD, so it was an odd choice of words failing to acknowledge this success.

[boxie]

so, bcache - still not worth it (at least for these use cases)

I would have honestly thought that bcache writeback would have been quicker. Michael any chance of you adding zfs with its zil/slog ssd options?

[phoronix]

Phoronix: HDD/SSD Performance With MDADM RAID, BCache On Linux 4.14

It's been one year since last testing BCache as a means in the Linux kernel's block layer to allow an SSD to serve as a cache for a larger but slower rotational hard drive. So I have carried out some fresh benchmarks using the Linux 4.14 Git kernel to provide not only fresh benchmarks of BCache but also MDADM SSD RAID on Linux and some other fresh SSD/HDD benchmarks.

http://www.phoronix.com/vr.php?view=25262