Date: Tue, 22 Sep 2015 09:26:53 +0200 From: InterNetX - Juergen Gotteswinter <jg@internetx.com> To: freebsd-fs@freebsd.org Subject: Re: [HAST] ZFS, many disks, write order Message-ID: <560102BD.6040703@internetx.com> In-Reply-To: <F332F505-F4B3-49D6-8CD7-B53496DCFF3E@gmail.com> References: <F332F505-F4B3-49D6-8CD7-B53496DCFF3E@gmail.com>
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One of the great Hast Features is that it Hides Disk Failures from ZFS,
this has been already discussed on this List a few Months ago.
Single ZIL Flash Drive is also not such a great Idea. I whould suggest
to start from scratch with "ZFS Best Practices".
Am 21.09.2015 um 23:10 schrieb Ben RUBSON:
> Hello,
>
> I plan to use HAST to synchronize a ZFS pool between 2 servers.
> The ZFS pool has 3 RAID-Z2 VDEVs (8+2), + 3 spares.
> +1 mirror for SLOG.
> +1 mirror for L2ARC.
> So a total of 37 disks (4TB each).
> 40Gb/s network bandwidth between the 2 servers.
>
> Will I have to define each of the 37 disks/resources in hast.conf ?
> Stupid question, but will this setup (with so many resources) work ?
>
> Will write IOs be ordered on the secondary node in the same order (over all the 37 devices) as they occurred on the primary node ?
> This of course to have the secondary node consistent, even after a power failure of the primary during a high IO load, leading into an import -F <poolname> on the secondary node.
>
> In HAST, each resource seems to be "independent" from the others.
> In DRBD, as an example, we can put several volumes in a same resource to guarantee write order over all the volumes (disks) of the resource.
> Example :
>
> resource r0 {
> volume 0 {
> device /dev/drbd0;
> disk /dev/c0v0;
> }
> volume 1 {
> device /dev/drbd1;
> disk /dev/c0v1;
> }
> }
>
> What about HAST then ?
> Of course I would have liked to have my 37 disks as volumes in the same resource, as in the example above.
>
> Thank you very much for your help !
>
> Best regards,
>
> Ben
>
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