Date: Fri, 22 Feb 2019 07:51:44 -0800 From: Enji Cooper <yaneurabeya@gmail.com> To: Rajesh Kumar <rajfbsd@gmail.com> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Any ideal way to run FIO benchmarking for NVMEe devices in FreeBSD Message-ID: <DEF69F8F-3CA0-448C-BA02-52A22CE8ECAB@gmail.com> In-Reply-To: <CAAO%2BANPUF8u54Xvu4uN=nRAEXaLNtBX%2BJkYzRbb5jrZMRTZ6gA@mail.gmail.com> References: <CAAO%2BANM34aY4g%2BFjPdt8F2sNo5e6N2dZdTDKavEJwvRbNJz=Gw@mail.gmail.com> <0E136DED-C1AD-481C-B243-C943D4F8D9C5@gmail.com> <CAAO%2BANPUF8u54Xvu4uN=nRAEXaLNtBX%2BJkYzRbb5jrZMRTZ6gA@mail.gmail.com>
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> On Feb 22, 2019, at 01:29, Rajesh Kumar <rajfbsd@gmail.com> wrote: >=20 > Hi Enji Cooper, >=20 > I am using Samsung 960 PRO >=20 > https://www.samsung.com/semiconductor/minisite/ssd/product/consumer/960pro= / Hi Rajesh, I asked about the datasheet, because there might be some hints in terms o= f the number of parallel jobs you might want to apply as well as the I/O que= ue depth, which will affect the performance of the drive. Otherwise you=E2=80= =99ll be throwing values against a wall, seeing what will stick, which is so= rt of ok if you bound your testing and adjust based on performance, but if y= our initial hunch is off, it can mislead you. Similarly, check to see if there are any tunables or sysctls that will b= ound the device in terms of the queue depth and I/O requests. As others have noted, test the device directly if you want to know its r= aw performance. Only test with a filesystem if your intent is to see how the= device will perform with a filesystem on it (and disable filesystem sync if= you want to test max throughput with the overhead of a filesystem). Testing= with a filesystem can reveal some potentially interesting characteristics, i= n terms of limitations in VFS / the filesystem implementation, which might b= e helpful if you=E2=80=99re trying to determine why there=E2=80=99s a differ= ence between raw device speed and the speed with a filesystem on it. Testing= with the same file in different directories is ok, as long as you blow the d= rive cache=E2=80=94which will have a noticeable performance impact on conven= tional (PMR, SMR, etc) drives, as you want to test the worst case speed of t= he device, instead of the cache. It should matter a bit less with faster dev= ices like SSDs/NVMe drives. Testing with files in the same lateral filesyste= m hierarchy (same directory), might reveal issues with filesystem locking (d= irectory inode performance), but that shouldn=E2=80=99t be the primary goal o= f your testing. It=E2=80=99s just something to keep in mind. Happy testing! HTH, -Enji=
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