Bug#702256: ITP: enhanceio -- dynamic block device cache for Linux
On Tue, Mar 5, 2013 at 1:42 PM, Dmitry Smirnov <onlyjob@member.fsf.org> wrote:
> On Tue, 5 Mar 2013 13:39:38 Liang Guo wrote:
>> JFYI: In linux 3.9-rc1, dm-cache are merged to mainstream kernel,
>
> Interesting, thank you.
> You're talking about https://github.com/mingzhao/dm-cache
> right?
>
> I've seen it but couldn't figure out how to use it...
> Nice to have it merged though even if it is not immediately useful...
>
I think the answer is No. mingzhao implemented dm-cache several yeas
ago, it was used to accelerate cd-rom or nfs access by using hard disk.
but had never been merged to upstream kernel. Several yeas later,
facebook created flashcache based on mingzhao's dm-cache when SSD
becomes popular, then STEC, Inc created enahnceIO based on flashcache.
DM-cache merged to upstream kernel in 3.9-rc1 is not the one wrote by
mingzhao, but from RedHat, I don't know whether it has any relation with
mingzhao's dm-cache. Its documents can be found at [1][2], the original
commit request is [3].
[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/device-mapper/cache.txt
[2] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/device-mapper/cache-policies.txt
[3] http://www.mail-archive.com/stable@vger.kernel.org/msg33526.html
STEC guyes has try to merge EnhanceIO to upstream[4], but it had not
been accepted.
[4] http://lwn.net/Articles/536018/
>
>> which can be used
>> to replace EnahnceIO/flashcache/bcache(IMO).
>
> IMHO bcache will never be a viable option due to maintenance overhead of
> custom patched kernel and (more important) because bcache require special
> preparation/formatting of block devices and therefore can't be plugged to
> existing file systems with data.
>
> I see that flashcache matured since 2011 and these days it doesn't cripple
> performance-wise as it used to.
>
> EnhancIO is just fantastic and (hopefully) immediately useful. Package is
> ready and only lacking reasonable testing so you're very welcome to try it. :)
>
>
> Regards,
> Dmitry Smirnov
> GPG key : 4096R/53968D1B
I have a brief look at the enhanceIO package, and have some suggestion:
1) Keep EnhanceIO source code in package VCS, this will simplify the
build procedure.
2) debian/patches/* is good cadidate for upstream, please don't keep
them in debian only.
3) README.Debian looks not debian specific, maybe a simple HOWTO
for upstream is better.
Thanks,
--
Liang Guo
http://bluestone.cublog.cn
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