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List: zfs-discuss
Subject: Re: [zfs-discuss] Zvol vs zfs send/zfs receive
From: Dave Pooser <dave.zfs () alfordmedia ! com>
Date: 2012-09-16 16:06:23
Message-ID: CC7B6185.A63BC%dave.lists () alfordmedia ! com
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On 9/16/12 10:40 AM, "Richard Elling" <richard.elling@gmail.com> wrote:
>With a zvol of 8K blocksize, 4K sector disks, and raidz you will get 12K
>(data
>plus parity) written for every block, regardless of how many disks are in
>the set.
>There will also be some metadata overhead, but I don't know of a metadata
>sizing formula for the general case.
>
>So the bad news is, 4K sector disks with small blocksize zvols tend to
>have space utilization more like mirroring. The good news is that
>performance
>is also more like mirroring.
> -- richard
Ok, that makes sense. And since there's no way to change the blocksize of
a zvol after creation (AFAIK) I can either live with the size, find 3TB
drives with 512byte sectors (I think Seagate Constellations would work)
and do yet another send/receive, or create a new zvol with a larger
blocksize and copy the files from one zvol to the other. (Leaning toward
option 3 because the files are mostly largish graphics files and the like.)
Thanks for the help!
--
Dave Pooser
Manager of Information Services
Alford Media http://www.alfordmedia.com
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