Date: Tue, 5 Jul 2016 12:37:33 +0200 From: Ben RUBSON <ben.rubson@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: HAST + ZFS + NFS + CARP Message-ID: <EDB52E2C-5815-4F7B-9476-CC37506AC488@gmail.com> In-Reply-To: <73DC3B93-60FF-4B20-AF80-5712F77818EF@ixsystems.com> References: <20160630144546.GB99997@mordor.lan> <71b8da1e-acb2-9d4e-5d11-20695aa5274a@internetx.com> <AD42D8FD-D07B-454E-B79D-028C1EC57381@gmail.com> <20160630153747.GB5695@mordor.lan> <63C07474-BDD5-42AA-BF4A-85A0E04D3CC2@gmail.com> <678321AB-A9F7-4890-A8C7-E20DFDC69137@gmail.com> <20160630185701.GD5695@mordor.lan> <FD296976-0250-4DA7-BB56-68F43B62C19B@ixsystems.com> <E9A65461-CD42-4CBD-9C22-87E1B9D5A4EA@gmail.com> <73DC3B93-60FF-4B20-AF80-5712F77818EF@ixsystems.com>
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> On 04 Jul 2016, at 20:06, Jordan Hubbard <jkh@ixsystems.com> wrote: >=20 >=20 >> On Jul 1, 2016, at 11:23 AM, Ben RUBSON <ben.rubson@gmail.com> wrote: >>=20 >> Would you say that giving an iSCSI disk to ZFS hides some details of = the raw disk to ZFS ? >=20 > Yes, of course. >=20 >> 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. >=20 > Not really, no. There are other ways of talking to a disk or SSD = device, such as getting S.M.A.R.T. data to see when/if a drive is = failing. Yep but SMART is not used by ZFS itself, according to a dev on #openzfs. There is however a feature request here : = https://github.com/zfsonlinux/zfs/issues/2777 I don't know whether FreeBSD iSCSI target implementation is SMART = pass-thru or not (I don't think so, my tests some months ago did not = work). However SMART data of iSCSI disks can easily be checked on the target = server itself (so not on the initiator, I agree) using smartmontools. > Drives also return checksum errors that may be masked by the iSCSI = target. Should be caught by smartmontools running on target, right ? > Finally, there is SCSI-2 and there is SCSI-3 (where things like = persistent reservations are implemented). None of these things are = necessarily implemented by iSCSI. At least FreeBSD implements persistent reservations : https://www.freebsd.org/cgi/man.cgi?query=3Dctl However I'm not sure ZFS itself uses such feature, which are more = relevant for clusters. Does it ? Ben
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