[sheepdog] 答复: [PATCH v2 1/2] sheep, dog: make recycling VID selectable

[redtone]

Many people want do daily snapshot (delete the old one and create a new one
with the save name)

-----邮件原件-----
发件人: sheepdog [mailto:sheepdog-bounces at lists.wpkg.org] 代表
moritakzt at nttdata.co.jp
发送时间: 2015年3月17日 11:56
收件人: sheepdog at lists.wpkg.org
主题: Re: [sheepdog] [PATCH v2 1/2] sheep, dog: make recycling VID
selectable

> > > I'm still not sure which code in vdi_lookup() is a problem.  The
> > > problem happens even when we disable VID garbage collection?
> >
> > vdi_lookup() becomes a problem if Hitoshi's patch is enabled after he
> > fixes a fatal bug of new algorithm.

I don't think Hitoshi says he will enable the new algorithm by default
after the fatal bug is fixed.  There is a performance problem as you
mentioned,
and I'm fine with making it disabled by default in future.

> 
> I need to add that, old sheep can reuse vid by checking inode's name, so
> vid recycling is unnecessary. It is proved simple and reliable, at the
cost
> of allow deleted inodes stored on the storage, but the space overhead is
> too small to notice.

If you are talking about reverting 21549a1b, it sounds wrong - it's not a
subtle bug fix but a critical one.
The old algorithm corrupts inode objects if we don't add --no-share option,
no?
Even if you think it's a corner use case, there is no technical way
to prevent users from doing the operation.

Thanks,

Kazutaka

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