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Date:      Wed, 20 Feb 2013 05:59:35 +0100
From:      "bsd@todoo.biz" <bsd@todoo.biz>
To:        Liste FreeBSD <freebsd-questions@freebsd.org>
Subject:   Re: ZFS + iSCSI architecture 
Message-ID:  <5A70C76B-4331-4BCA-82D3-3A6E6ADF7032@todoo.biz>
In-Reply-To: <A1618B03-9CA6-46F9-89CA-7DB38B5D6ECA@my.gd>
References:  <93B2D1C4-8887-45F9-9939-A099AC5E3DA0@todoo.biz> <A1618B03-9CA6-46F9-89CA-7DB38B5D6ECA@my.gd>

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Le 20 f=E9vr. 2013 =E0 02:14, Fleuriot Damien <ml@my.gd> a =E9crit :

>=20
> On Feb 19, 2013, at 11:20 PM, "bsd@todoo.biz" <bsd@todoo.biz> wrote:
>=20
>> Hello,
>>=20
>>=20
>> I am about to start deploying a large system (about 18 To which can =
grow up to 36 To) based on a big Intel platform with lot's of fancy =
features to have turbo boosted platform (ZIL on SSD + system on dongle =
if I go for FreeNAS). Since I want to move on quite fast I might decide =
to use FreeNAS in it's latest version.=20
>>=20
>>=20
>> The idea behind all that was to grant 5 or six critical servers =
access to the NAS so that they can take advantage of :=20
>>=20
>> 1. space available on the NAS
>>=20
>> 2. ability of the NAS to use ZFS and of clients to support this file =
system (including snapshots)=20
>>=20
>> 3. Access the server using iSCSI (at least this is what I initially =
planned).=20
>>=20
>> 4. Mount part of their filesystem using data stored on the SAN (like =
/usr/local/ or other parts of the system).=20
>>=20
>>=20
>>=20
>> The server accessing the data will be of two types :=20
>>=20
>> 1. 2 x Ubuntu server 10.04 LTS=20
>>=20
>> 2. 4 x FreeBSD (mainly 8 and 9) with jail configured=20
>>=20
>>=20
>> I have started reading about iSCSI and potential problems with =
FreeBSD.=20
>>=20
>=20
> What problems do you mean ?

For example :=20

- Can my client (the initiator) directly mount a ZFS volume on freeBSD =
using iSCSI or should I go back to formatting It to UFS ?

- Is the iSCSI stack in FreeBSD stable an mature enough to be used in a =
production environment ?
=3D=3D> It is out of scope to have kernel panic because of an unstable =
iSCSI related problem.=20


>=20
>> So my main questions would be :=20
>>=20
>>=20
>> =95 Should I go for iSCSI ?=20
>>=20
>=20
> Well in all use cases, iscsi should perform faster than NFS.

Fast is good - stable is necessary in this case !=20
And this is what I am tring to evaluate=85=20

>=20
>> =95 Should I rather choose / prefer NFS ?=20
>>=20
>> =95 Should I export a Volume as UFS rather than ZFS (is ZFS supported =
as a target) ?
>>=20
>=20
> I'm not sure what you mean here, when you export a zvol over ISCSI:
> - your SAN is the target and presents a block device (the zvol)
> - your client is the initiator
> - your client attaches to the ISCSI drive and formats it using =
filesystem XYZ, be it ext3, ufs or ntfs
>=20

Thanks for this reminder about vocabulary for iSCSI, I'll try to stick =
to It ;-)=20

>=20
>>=20
>> The main idea is stability, redundancy of data and ease of =
maintenance (in a headless FreeBSD / Linux world) before anything else !=20=

>>=20
>=20
> ISCSI is a bit harder to setup IMO, however I think it''s more =
reliable than NFS, what with its auto retries if it loses the network =
link to a device.
>=20

Have you deployed this in production and what are your concerns and =
recommendations ?=20

>=20
>=20
>>=20
>>=20
>> That's the big pictures, if you have any pointers, advise, they are =
all welcome.=20
>>=20
>>=20
>> It is quite late where I leave, so I will reply to posts in 8 to 10 =
hours, but I hope to have enough answer(s) to start an interesting =
thread (as I think this question is very interesting and not so clearly =
explained (at least in my mind))=85=20
>>=20
>=20
> This is idd a very interesting topic and I hope to see more :)
>=20

There is also an interesting (and fresh) post here :=20

=
http://utcc.utoronto.ca/~cks/space/blog/solaris/ZFSFreeBSDvsIllumos?showco=
mments#comments

>=20
>>=20
>> Thx very much for your infos and feedback.=20
>=20
>=20

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