Avi Kivity wrote:
Bill Davidsen wrote:
> Not syncing unused area is possible, if there was a way for raid resync
> to ask the fs what blocks are not in use. I.e. get the
> free block list in disk block order. Then raid resync could skip
those.
>
Current RAID code supports having a bitmap of dirty stripes, and can
just sync those during recovery. I'm sure Neil could explain it better,
but this is available without worrying about fs type. Now. Today.
This is only when the you reconstruct a disk that was once part of the
RAID. If you are adding a brand new disk, all stripes are dirty.
I will leave Neil to explain this to you, it appears to be a totally
different case for reconfiguration, but I don't pretend to understand
the code well enough to clarify it.
This happens in two scenarios: an unclean RAID shutdown, and when you
have a remote mirror which can be disconnected by network problems.
If the RAID is integrated in the filesystem (or into an object storage
system), you can handle the new disk case too.
I'm not sure that building the RAID into the filesystem is ever a good
idea, it certainly seems likely to either prevent certain RAID devices
from being used, or make them perform suboptimally. There are times when
being able to move a filesystem to a new device is REALLY useful, and
byte copy is more practical than file by file copy.
--
Bill Davidsen <[email protected]>
Obscure bug of 2004: BASH BUFFER OVERFLOW - if bash is being run by a
normal user and is setuid root, with the "vi" line edit mode selected,
and the character set is "big5," an off-by-one errors occurs during
wildcard (glob) expansion.
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