[linux-lvm] mirror_region_size default: 4096 six times faster than 512?

[Ray Morris]

> copying chunks of a few MBs seems to always beat copying
> > bytes or KB per chunk.

> What kind of RAID?  Anything that involves parity is going to require
> small writes to read and merge the new data into blocks and rewrite
> the parity.

At least mdadm RAID1  and RAID5.  Hardware raid5 was slow with 512,
but not yet tested with 4096 or higher. I'll test it in a few days 
after a migration completes.
-- 
Ray Morris
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On Fri, 24 Feb 2012 09:57:30 -0600
Les Mikesell <lesmikesell at gmail.com> wrote:

> On Thu, Feb 23, 2012 at 10:46 AM, Ray Morris <support at bettercgi.com>
> wrote:
> > 512 byte sector consumer SATA drives from Seagate and Hitachi.
> > Drives attached to a 9560 RAID card exhibited more difference than
> > drives in a different system attached to the motherboard directly.
> > As I mentioned, I haven't done extensive or highly scientific
> > testing, but in general, across various hardware using various
> > software, copying chinks of a few MBs seems to always beat copying
> > bytes or KB per chunk.
> 
> 
> What kind of RAID?  Anything that involves parity is going to require
> small writes to read and merge the new data into blocks and rewrite
> the parity.
>