Re: Btrfs: broken file system design
From: Andi Kleen
Date: Fri Jun 25 2010 - 05:16:04 EST
"Daniel Taylor" <Daniel.Taylor@xxxxxxx> writes:
> As long as no object smaller than the disk block size is ever
> flushed to media, and all flushed objects are aligned to the disk
> blocks, there should be no real performance hit from that.
The question is just how large such a block needs to be.
Traditionally some RAID controllers (and possibly some SSDs now)
needed very large blocks upto MBs.
> Otherwise we end up with the damage for the ext family, where
> the file blocks can be aligned, but the 1K inode updates cause
> the read-modify-write (RMW) cycles and and cost >10% performance
> hit for creation/update of large numbers of files.
Fixing that doesn't require a new file system layout, just some effort
to read/write inodes in batches of multiple of them. XFS did similar
things for a long time, I believe there were some efforts for this
for ext4 too.
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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