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LWN.net Weekly Edition for May 23, 2013
An "enum" for Python 3
An unexpected perf feature
LWN.net Weekly Edition for May 16, 2013
A look at the PyPy 2.0 release
What about the EnhanceIO driver that is aiming at 3.10 merge window? I assume that they are similar code accomplishing similar job, no?
The conclusion of the 3.9 merge window
Posted Mar 6, 2013 12:33 UTC (Wed) by Tobu (subscriber, #24111)
Posted Mar 8, 2013 2:27 UTC (Fri) by msnitzer (subscriber, #57232)
Posted Mar 6, 2013 13:48 UTC (Wed) by ebirdie (subscriber, #512)
>Bcache is a Linux kernel block layer cache. It allows one or more fast disk drives such as flash-based solid state drives (SSDs) to act as a cache for one or more slower hard disk drives.
Posted Mar 6, 2013 14:48 UTC (Wed) by Tobu (subscriber, #24111)
Posted Mar 7, 2013 8:05 UTC (Thu) by ebirdie (subscriber, #512)
Posted Mar 8, 2013 2:37 UTC (Fri) by msnitzer (subscriber, #57232)
But we definitely need to definitely update the bcache and enhanceio code.
Also, please note that there are some dm-cache fixes that will likely be sent to Linus for 3.9-rc2 that Alasdair (DM maintainer) has staged here: http://people.redhat.com/agk/patches/linux/editing/series...
Posted Mar 8, 2013 17:30 UTC (Fri) by Lennie (subscriber, #49641)
It is kinda annoying, I know.
But if a normal block device would be used as a backing store there is nothing to preventing accidental use even though there might be dirty data on the cache device.
The EnhanceIO developers use some udev scripts to prevent this, I haven't looked at how they do it. I guess that could work, the EnhanceIO developers said they haven't seen any problems yet. But I can definitely see why the bcache developer made his choice.
If a cachesystem would have be integrated in the filesystem the filesystem could have something recorded which would prevent it from being mounted without the user forcing it in some way when the cache device is never coming back.
It is kinda interesting to see there are 6 ways/ideas floating around to do caching or caching related things now for the Linux kernel:
- dm-cache, now in the kernel I guess
- Facebook Flashcache
- Google bcache
- EnhanceIO was based on Flashcache I believe
- If I'm not mistake in recent kernels there is code in the VFS which keeps track of which data is hot
- btrfs developers are looking at doing something in btrfs, if I remember correctly they have expressed some interest in the VFS solution
The dm-cache, EnhanceIO and bcache have 'spoken' on the mailinglist and one even mentioned he didn't see any problem in having several implementations in the mainline kernel.
I'm not so sure Linus would even accept those patches. :-)
It is interesting and maybe sometimes seems a bit painful to see that many different efforts. They obviously all have their strengths and weaknesses of course.
Posted Mar 8, 2013 17:49 UTC (Fri) by Lennie (subscriber, #49641)
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