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Message-ID: <20140506152129.GA31730@thunk.org> Date: Tue, 6 May 2014 11:21:29 -0400 From: Theodore Ts'o <tytso@....edu> To: Lukáš Czerner <lczerner@...hat.com> Cc: "Darrick J. Wong" <darrick.wong@...cle.com>, linux-ext4@...r.kernel.org Subject: Re: [PATCH 37/37] ext5: define new subtype to add features and reduce testing complexity On Tue, May 06, 2014 at 02:50:39PM +0200, Lukáš Czerner wrote: > meta_bg - Just makes group descriptors to be spread across the file > system. It has been around for some time and I am not sure > why this is not a default already. It should also increase > the limit of the file system size but I am not sure whether > this is still true with flex_bg ? meta_bg signiicantly slows down mount operations (and in general, any operation where we need to read in the block group descriptors --- i.e., dumpe2fs, e2fsck, etc.) The strategy for meta_bg is that it's something that we enable as we need it, as part of an online or off-line resize. That way, we keep the block groups contiguous for as long as possible. Once the resize inode has been exhausted (which _will_ happen when the file system size grows beyond 16T), the resize operation will turn off the resize_inode feature and then enable the meta_bg feature. And this is all working today, with the latest kernel and e2fsprogs; so there's no reason to enable meta_bg as part of mke2fs operation, and a good reason not to enable it by default, but to let resize2fs turn it on when it makes sense to do so. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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