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Re: btrfs and 1 billion small files



On 08/05/12 13:31, Chris Mason wrote:

[...]
> A few people have already mentioned how btrfs will pack these small
> files into metadata blocks.  If you're running btrfs on a single disk,

[...]
> But the cost is increased CPU usage.  Btrfs hits memmove and memcpy
> pretty hard when you're using larger blocks.
> 
> I suggest using a 16K or 32K block size.  You can go up to 64K, it may
> work well if you have beefy CPUs.  Example for 16K:
> 
> mkfs.btrfs -l 16K -n 16K /dev/xxx

Is that still with "-s 4K" ?


Might that help SSDs that work in 16kByte chunks?

And why are memmove and memcpy more heavily used?

Does that suggest better optimisation of the (meta)data, or just a
greater housekeeping overhead to shuffle data to new offsets?


Regards,
Martin


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