linux-kernel - Re: VFAT truncate performance

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Message-ID: <8764g28il3.fsf@duaron.myhome.or.jp>
Date:	Tue, 05 Sep 2006 23:59:52 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Mattias Rönnblom <hofors@...ator.liu.se>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: VFAT truncate performance

Mattias Rönnblom <hofors@...ator.liu.se> writes:

> extending files by ftruncate(2) runs very slow on VFAT file
> systems. On my USB harddisk w/ VFAT, it takes 14 seconds to extend an
> empty file to 1 GB. On a memory stick, it takes well over 4 minutes.
>
> My question is: is this problem on the conceptual level (ie there is
> no way of extending files on FAT that doesn't involve many disk
> operations) or is the current Linux fs driver suboptimal in this
> respect?

Unfortunately FAT doesn't support sparse file, so ftruncate(2) which
extend size needs to fill all clusters with zero, and write data.

This is limitation of FAT filesystem.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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