Date: Thu, 2 Feb 2023 09:04:02 -0700 From: Alan Somers <asomers@freebsd.org> To: jbo@insane.engineer Cc: "hackers@freebsd.org" <hackers@freebsd.org> Subject: Re: Swap, ZFS & ARC Message-ID: <CAOtMX2iDupBJkPuNzpACivdxVKKKW_rHFFkaNexsSfbeCc-YBw@mail.gmail.com> In-Reply-To: <c70BKF1xrExMKWQeTJtDhOqJVqISFp9RjHFwT0XWDh3sTXyi0NMRkVhOyp_YkTXXAV7Dtm4tK4_XsOwSXuZRT39ObYtFpPoe6biv22jMNnM=@insane.engineer> References: <ysSGWaXF7vCDubzgFdov_9k6SMLNdZ3-zHV-2LOraYOxV_8yoAkDVPqDSicYsgBw1KdL6BjP4FkK1KFs7NKZ4RRXcSDxVe_Qy_i7b_5AbSI=@insane.engineer> <1689ba8c-a317-ce1f-2854-99566468a9ed@grosbein.net> <c70BKF1xrExMKWQeTJtDhOqJVqISFp9RjHFwT0XWDh3sTXyi0NMRkVhOyp_YkTXXAV7Dtm4tK4_XsOwSXuZRT39ObYtFpPoe6biv22jMNnM=@insane.engineer>
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On Thu, Feb 2, 2023 at 8:45 AM <jbo@insane.engineer> wrote: > > > > > > > ------- Original Message ------- > On Thursday, February 2nd, 2023 at 14:41, Eugene Grosbein <eugen@grosbein= .net> wrote: > > > > > > > > 02.02.2023 21:28, jbo@insane.engineer wrote: > > > > > Hello folks, > > > > > > Based on a discussion on the forums not so long ago I tried to figure= out how swap usage on a ZFS system plays together with ARC. However, I cou= ld find very little to no information on this which leads me to believe tha= t there is some "core concept" I might be oblivious to. > > > > > > The main question is basically this: Your system starts to swap out d= ata from RAM to your swap partition. > > > This swap data on disk ultimately resides somewhere in a ZFS pool. > > > > > > I prefer not doing this. That is, all my systems have swap partition ou= tside of ZFS pool. > > This isn't really achievable on your average "single disk" desktop system= s, right? > Assuming I'm not missing something (which is why I came here to ask), a "= regular" or "default" installation through the FreeBSD installer would setu= p a swap partition within the zpool, right? Actually, the installer by default sets up a swap partition beside the zroot pool. It doesn't use swap-on-zvol. Here's what it looks like: > gpart show =3D> 40 1953525088 nvd0 GPT (932G) 40 532480 1 efi (260M) 532520 1024 2 freebsd-boot (512K) 533544 984 - free - (492K) 534528 16777216 3 freebsd-swap (8.0G) 17311744 1936211968 4 freebsd-zfs (923G) 1953523712 1416 - free - (708K) =3D> 40 1953525088 nvd1 GPT (932G) 40 532480 1 efi (260M) 532520 1024 2 freebsd-boot (512K) 533544 984 - free - (492K) 534528 16777216 3 freebsd-swap (8.0G) 17311744 1936211968 4 freebsd-zfs (923G) 1953523712 1416 - free - (708K) > zpool status zroot pool: zroot state: ONLINE scan: resilvered 314G in 00:10:19 with 0 errors on Sat Dec 24 22:31:04 20= 22 config: NAME STATE READ WRITE CKSUM zroot ONLINE 0 0 0 mirror-0 ONLINE 0 0 0 nvd0p4 ONLINE 0 0 0 nvd1p4 ONLINE 0 0 0 > swapinfo Device 1K-blocks Used Avail Capacity /dev/gpt/swap0 8388608 0 8388608 0%
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