On 11/09/2009 03:22 PM, Neil F Brown wrote:
> On Tue, November 10, 2009 1:39 am, Doug Ledford wrote:
>> On 11/06/2009 01:45 AM, Neil Brown wrote:
>>>
>>> Greetings.
>>>
>>> About a week ago I released mdadm-3.1
>>> I have now 'withdrawn' it meaning that it doesn't appear on the
>>> kernel.org mirrors any more, and I ask people not to use it.
>>
>> Although the cause for this sucks, I was actually going to suggest that
>> since 3.1 is a version bump, that we take the opportunity to change a
>> few defaults. Like switching to version 1 superblocks instead of
>> version 0 by default. And changing the default chunk size to 512k
>> instead of 64k. The time has simply come for the 0->1 superblock
>> change, and I have a good deal of data showing that for SATA disks at
>> least, the 512k chunk size is the typical sweet spot.
>
> I had been toying with that idea myself - certainly of changing the
> defaults soon.
> I'm tempted to make the default metadata "1.1" though possibly not for
> RAID1. For RAID0,4,5,6,10 there is no value in having the metadata
> at the end of the device. For RAID1 there is as it makes booting off
> any member easier.
> Thoughts?
While it makes booting off of a raid1 easier, raid1 is *precisely* the
level that is prone to silent data corrupt due to the individual members
being able to be mounted while not part of a running raid array. I
would make it default to 1.1 period, and force distros or other people
to either A) update the boot loader to something that can handle a 1.1
superblock (grub2 should be able to) or B) manually set it to 1.0 instead.
>
> I'm certainly happy with increasing the chunksize to 512K.
>
> NeilBrown
--
Doug Ledford <dledford@xxxxxxxxxx>
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