linux-ext4 - Re: mke2fs options for large media archive filesystem

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Message-Id: <F3EDB2EF-E089-486A-B1FC-6395770B111E@dilger.ca>
Date:	Sun, 2 Feb 2014 18:30:13 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Vitaliy Filippov <vitalif@...rcmc.ru>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Bastien Traverse <bastien.traverse@...il.com>
Subject: Re: mke2fs options for large media archive filesystem

I would say that bigalloc is probably not what you want for an archival system. It is relatively new and the space savings is minimal. It is mostly for filesystems that need to allocate and free large files rapidly. 

Note that with bigalloc you will also be allocating directories at the bigalloc cluster size? Which will be too large in most cases. 

Since you already know the average file size, using -i {average size} is what you want. The -N option is just a different way of specifying the same thing, the underlying filesystem ends up being the same.

I would also recommend to allocate about 2x the inodes you think you will need. If there are suddenly thumbnails of the photos or key photos for videos then you don't want to run out of inodes. 

Cheers, Andreas

> On Feb 2, 2014, at 9:35, "Vitaliy Filippov" <vitalif@...rcmc.ru> wrote:
> 
> Hi,
> 
>> b) bigalloc feature
> 
> As I understand (please correct me someone if I'm wrong), given that ext4 uses extents, bigalloc feature is really useful ONLY for minimizing block bitmaps. Which is probably only useful for (maybe) reducing kernel memory usage and for (maybe) reducing fragmentation. 'maybe' means I personally don't know if benefit will be large enough, and I even don't know if there would be any real benefit at all... I didn't see any real bigalloc tests in the web...
> 
> So, I personally don't think you'll really benefit from bigalloc on a 1TB archive partition... But I would like it very much if someone can tell an authoritative verdict. :)
> 
> -- 
> With best regards,
>  Vitaliy Filippov
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