Hi Kris, Le 2018-02-06 à 10:24, Kris Davis a écrit :
The performance variation you mention below doesn't sound unusual for a non-preconditioned SSD. You didn't mention what sort of "preconditioning" you did to the SSDs prior to your measurements. You may be unaware that SSDs require some usually extensive preconditioning operations to obtain stable results. Take a look at the SNIA test methodology for a pretty good explanation (http://www.snia.org/sites/default/files/SSS_PTS_Enterprise_v1.1.pdf) I think starting around page 18.
I think you hit the nail on the head here. I didn't do any sort of preconditioning, as I didn't think it necessary. To test this, I created a logical volume and an ext4 filesystem on top the the md device and ran the same test except with a fixed-size IO file of 10G.
I noticed that at the beginning, fio "lays out" this file, which may be just enough "preconditioning" because then the random writes are much more stable at the beginning and the curve observed in the previous test is absent.
Thanks, -- Jerome -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
