Date: Wed, 7 Feb 2024 14:36:18 +0100 From: Andrea Brancatelli <andrea@brancatelli.it> To: Ben RUBSON <ben.rubson@gmx.com> Cc: fs@freebsd.org Subject: Re: ZFS on a shared iSCSI Message-ID: <CAGqQmRMJp8Rs6ZChkrqRm1sDpjKjj%2B2n=hT2nUk1Nsq6pfOQnw@mail.gmail.com> In-Reply-To: <FADEDED8-7C34-4C14-A251-00F4EFBEE6ED@gmx.com> References: <CAGqQmRPssfrb9S6r0H4SaQLEfOTp5Qx7-HSvHtYkxMnpeqKWjQ@mail.gmail.com> <FADEDED8-7C34-4C14-A251-00F4EFBEE6ED@gmx.com>
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--0000000000004681040610cac869 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Feb 7, 2024 at 12:25=E2=80=AFPM Ben RUBSON <ben.rubson@gmx.com> wro= te: > > On 7 Feb 2024, at 11:55, Andrea Brancatelli <andrea@brancatelli.it> > wrote: > > > > Would it be "easily possible" to have some (2?) iSCSI LUN exposed to > both servers and then activate the pool on one or the other server? > > Hi Andrea, > > Yes, I have such configurations : > 2 servers with same JBODs configuration. > When zpool is mounted on server A, mirroring is done on both local disks > and iSCSI disks from server B. > When zpool is mounted on server B, mirroring is done on both local disks > and iSCSI disks from server A. > Works flawlessly. > And you can have one of the 2 servers offline for some time, when it will > be back online, sync will restart. > What you can't have is zpool online on both servers at the same time. > > So you can do the same with iSCSI disks only. > Disks will have to be mounted on one server at a time only. > > You'll have to have a rather low network / iSCSI latency, or it will fail > / zpool will be unusable. > If you have high latency, you'll have to go for ZFS send/receive. > That sounds like an interesting setup, although we have an external iSCSI "SAN" so the iSCSI approach would be totally offloaded, without any local storage. Imagine Server A having a certain LUN on the iSCSI device and Server B having another one. If a server fails, the idea would be to activate the pool "on the fly" on the other one. Otherwise I totally take iSCSI out of the picture (less is better), have local disks and zfs-snapshot stuff back and forth. --=20 *Andrea Brancatelli* --0000000000004681040610cac869 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote"><div= dir=3D"ltr" class=3D"gmail_attr">On Wed, Feb 7, 2024 at 12:25=E2=80=AFPM B= en RUBSON <<a href=3D"mailto:ben.rubson@gmx.com" target=3D"_blank">ben.r= ubson@gmx.com</a>> wrote:<br></div><blockquote class=3D"gmail_quote" sty= le=3D"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:soli= d;border-left-color:rgb(204,204,204);padding-left:1ex">> On 7 Feb 2024, = at 11:55, Andrea Brancatelli <<a href=3D"mailto:andrea@brancatelli.it" t= arget=3D"_blank">andrea@brancatelli.it</a>> wrote:<br> > <br> > Would it be "easily possible" to have some (2?) iSCSI LUN ex= posed to both servers and then activate the pool on one or the other server= ? <br> <br> Hi Andrea,<br> <br> Yes, I have such configurations :<br> 2 servers with same JBODs configuration.<br> When zpool is mounted on server A, mirroring is done on both local disks an= d iSCSI disks from server B.<br> When zpool is mounted on server B, mirroring is done on both local disks an= d iSCSI disks from server A.<br> Works flawlessly.<br> And you can have one of the 2 servers offline for some time, when it will b= e back online, sync will restart.<br> What you can't have is zpool online on both servers at the same time.<b= r> <br> So you can do the same with iSCSI disks only.<br> Disks will have to be mounted on one server at a time only.<br> <br> You'll have to have a rather low network / iSCSI latency, or it will fa= il / zpool will be unusable.<br> If you have high latency, you'll have to go for ZFS send/receive.<br></= blockquote><div><br></div><div>That sounds like an interesting setup, altho= ugh=C2=A0we have an external iSCSI "SAN" so the iSCSI approach wo= uld be totally offloaded, without any local storage.</div><div><br></div><d= iv>Imagine Server A having a certain LUN on the iSCSI device and Server B h= aving another one.</div><div><br></div><div>If a server fails, the idea wou= ld be to activate the=C2=A0pool "on the fly" on the other one.</d= iv><div><br></div><div>Otherwise I totally take iSCSI out of the picture (l= ess is better), have local disks and zfs-snapshot stuff back and forth.</di= v><div><br></div><div><br></div><div>=C2=A0</div></div><br clear=3D"all"><d= iv><br></div><span class=3D"gmail_signature_prefix">-- </span><br><div dir= =3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><b>Andrea Brancatelli</= b><div><b><br></b></div></div></div></div> --0000000000004681040610cac869--
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