Date: Tue, 29 Jan 2013 12:06:27 +0100 From: Olivier Smedts <olivier@gid0.org> To: Adam Nowacki <nowakpl@platinum.linux.pl> Cc: Matthew Ahrens <mahrens@delphix.com>, fs@freebsd.org Subject: Re: RAID-Z wasted space - asize roundups to nparity +1 Message-ID: <CABzXLYMOK0ZDeDw95se1LZShaCowH1k7CZV7vkHdbkmwbZ9eDQ@mail.gmail.com> In-Reply-To: <5107A9B7.5030803@platinum.linux.pl> References: <5105252D.6060502@platinum.linux.pl> <CAJjvXiEQSqnKYP75crTkgVqLKSk92q9UTikFtdyPHmF6shJFbg@mail.gmail.com> <5107A9B7.5030803@platinum.linux.pl>
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2013/1/29 Adam Nowacki <nowakpl@platinum.linux.pl>:
> This brings another issue - recordsize capped at 128KiB. We are using the
> pool for off-line storage of large files (from 50MB to 20GB). Files are
> stored and read sequentially as a whole. With 12 disks in RAID-Z2, 4KiB
> sectors, 128KiB record size and the padding above 9.4% of disk space goes
> completely unused - one whole disk.
>
> Increasing recordsize cap seems trivial enough. On-disk structures and
> kernel code support it already - a single of code had to be changed (#define
> SPA_MAXBLOCKSHIFT - from 17 to 20) to support 1MiB recordsizes. This of
> course breaks compatibility with any other system without this modification.
> With Suns cooperation this could be handled in safe and compatible manner
> via pool version upgrade. Recordsize of 128KiB would remain the default but
> anyone could increase it with zfs set.
One MB blocksize is already implemented by Oracle with zpool version 32.
--
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