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Date:      Mon, 4 Jul 2016 11:06:34 -0700
From:      Jordan Hubbard <jkh@ixsystems.com>
To:        Ben RUBSON <ben.rubson@gmail.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: HAST + ZFS + NFS + CARP
Message-ID:  <73DC3B93-60FF-4B20-AF80-5712F77818EF@ixsystems.com>
In-Reply-To: <E9A65461-CD42-4CBD-9C22-87E1B9D5A4EA@gmail.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>

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> 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 ?

Yes, of course.

> 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.

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.  Drives also return checksum errors that may be masked by the =
iSCSI target.  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.

- Jordan




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