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[90.116.246.85]) by smtp.gmail.com with ESMTPSA id n26sm3267499wmi.3.2016.07.02.08.03.50 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Sat, 02 Jul 2016 08:03:51 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: HAST + ZFS + NFS + CARP From: Ben RUBSON In-Reply-To: Date: Sat, 2 Jul 2016 17:03:50 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <868B90CB-828F-48E8-B678-50FC1BB52FAE@gmail.com> References: <20160630144546.GB99997@mordor.lan> <71b8da1e-acb2-9d4e-5d11-20695aa5274a@internetx.com> <20160630153747.GB5695@mordor.lan> <63C07474-BDD5-42AA-BF4A-85A0E04D3CC2@gmail.com> <678321AB-A9F7-4890-A8C7-E20DFDC69137@gmail.com> <20160630185701.GD5695@mordor.lan> To: freebsd-fs@freebsd.org X-Mailer: Apple Mail (2.3124) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 02 Jul 2016 15:03:54 -0000 > On 01 Jul 2016, at 20:23, Ben RUBSON wrote: >=20 >=20 >> On 01 Jul 2016, at 19:54, Jordan Hubbard wrote: >> (...) >> And yes, of course one can layer additional things on top of iSCSI = LUNs, just as one can punch through LUNs from older SAN fabrics and put = ZFS pools on top of them (been there, done both of those things), though = of course the additional indirection has performance and debugging = ramifications of its own (when a pool goes sideways, you have additional = things in the failure chain to debug). ZFS really likes to =E2=80=9Cown = the disks=E2=80=9D in terms of providing block-level fault tolerance and = predictable performance characteristics given specific vdev topologies, = and once you start abstracting the disks away from it, making statements = about predicted IOPs for the pool becomes something of a =E2=80=9C???=E2=80= =9D exercise. >=20 > Would you say that giving an iSCSI disk to ZFS hides some details of = the raw disk to ZFS ? > I though that iSCSI would have been a totally "transparent" layer, = transferring all ZFS requests to the raw disk, giving back the answers, = hiding anything. =46rom #openzfs : A: typically iSCSI disks still appear as "physical" disks to the OS = connecting to them. you can even get iSCSI servers that allow things = like SMART pass-thru Q: so ZFS will be as happy with iSCSI disks as if it used local disks ? = or will it miss something ? A: no, and ZFS isn't "unhappy" per se. but there are optimizations it = applies when it knows the disks belong to ZFS only Q: and using iSCSI disks, ZFS will not apply these optimizations (even = if these iSCSI disks are only given to ZFS) ? ie, will ZFS know these = iSCSI disks belong to ZFS only ? A: if it looks like a physical disk, if it quacks like a physical = disk...=