Date: Mon, 7 Mar 2016 13:06:59 +0800 From: Fred Liu <fred.fliu@gmail.com> To: developer@lists.open-zfs.org Cc: "smartos-discuss@lists.smartos.org" <smartos-discuss@lists.smartos.org>, developer <developer@open-zfs.org>, illumos-developer <developer@lists.illumos.org>, omnios-discuss <omnios-discuss@lists.omniti.com>, Discussion list for OpenIndiana <openindiana-discuss@openindiana.org>, illumos-zfs <zfs@lists.illumos.org>, "zfs-discuss@list.zfsonlinux.org" <zfs-discuss@list.zfsonlinux.org>, "freebsd-fs@FreeBSD.org" <freebsd-fs@freebsd.org>, "zfs-devel@freebsd.org" <zfs-devel@freebsd.org> Subject: Re: [developer] Re: [smartos-discuss] an interesting survey -- the zpool with most disks you have ever built Message-ID: <CALi05Xxm9Sdx9dXCU4C8YhUTZOwPY%2BNQqzmMEn5d0iFeOES6gw@mail.gmail.com> In-Reply-To: <5158F354-9636-4031-9536-E99450F312B3@RichardElling.com> References: <95563acb-d27b-4d4b-b8f3-afeb87a3d599@me.com> <CACTb9pxJqk__DPN_pDy4xPvd6ETZtbF9y=B8U7RaeGnn0tKAVQ@mail.gmail.com> <CAJjvXiH9Wh%2BYKngTvv0XG1HtikWggBDwjr_MCb8=Rf276DZO-Q@mail.gmail.com> <56D87784.4090103@broken.net> <A5A6EA4AE9DCC44F8E7FCB4D6317B1D203178F1DD392@SH-MAIL.ISSI.COM> <5158F354-9636-4031-9536-E99450F312B3@RichardElling.com>
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2016-03-06 22:49 GMT+08:00 Richard Elling <richard.elling@richardelling.com=
>
:
>
> On Mar 3, 2016, at 8:35 PM, Fred Liu <Fred_Liu@issi.com> wrote:
>
> Hi,
>
> Today when I was reading Jeff's new nuclear weapon -- DSSD D5's CUBIC RAI=
D
> introduction,
> the interesting survey -- the zpool with most disks you have ever built
> popped in my brain.
>
>
> We test to 2,000 drives. Beyond 2,000 there are some scalability issues
> that impact failover times.
> We=E2=80=99ve identified these and know what to fix, but need a real cust=
omer at
> this scale to bump it to
> the top of the priority queue.
>
> [Fred]: Wow! 2000 drives almost need 4~5 whole racks!
>
> For zfs doesn't support nested vdev, the maximum fault tolerance should b=
e
> three(from raidz3).
>
>
> Pedantically, it is N, because you can have N-way mirroring.
>
[Fred]: Yeah. That is just pedantic. N-way mirroring of every disk works in
theory and rarely happens in reality.
>
> It is stranded if you want to build a very huge pool.
>
>
> Scaling redundancy by increasing parity improves data loss protection by
> about 3 orders of
> magnitude. Adding capacity by striping reduces data loss protection by
> 1/N. This is why there is
> not much need to go beyond raidz3. However, if you do want to go there,
> adding raidz4+ is
> relatively easy.
>
[Fred]: I assume you used stripped raidz3 vedvs in your storage mesh of
2000 drives. If that is true, the possibility of 4/2000 will be not so low.
Plus, reslivering takes longer time if single disk has bigger
capacity. And further, the cost of over-provisioning spare disks vs raidz4+
will be an deserved
trade-off when the storage mesh at the scale of 2000 drives.
Thanks.
Fred
>
>
> --
>
> Richard.Elling@RichardElling.com <Richard.Elling@richardelling.com>
> +1-760-896-4422
>
>
>
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