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Date: Mon, 29 Mar 2010 09:48:50 -0500 From: Eric Sandeen <sandeen@...hat.com> To: CaT <cat@....com.au> CC: linux-ext4@...r.kernel.org Subject: Re: 2.6.33.1: ext4 disk free weirdness CaT wrote: > Using kernel 2.6.33.1. Am rsyncing from /data/mirror (a raid0 mount) to > /dev/sda1 (a usb HD). Both filesystems formatted as ext3 but mounted as > ext4. /mnt filesystem is only being added to and currently large files > (iso files 700MB-4.4GB) are being copied. When I remounted /mnt as ext3 > I could not duplicate the issue and the amount of disk used stabilised > at 182G. The df results, whilst /mnt is mounted as ext4, are below: I would say this is likely speculative allocation due to delalloc (ext4 has to reserve worst-case metadata amounts to prepare for delalloc writeback). When the file data actually gets written out, the worst-case reservation is freed up again. We also flush and switch to nodelalloc when the filesystem is pretty close to full. see ext4_nonda_switch() for example. This looks pretty severe though, more than I would expect from that behavior. Some interesting tests would be to try it again -o nodelalloc (I expect the behavior to go away) and maybe to copy a single large file and see how bad the overshoot is before and after a "sync". -Eric > 1 [29/03 15:05:58] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 317G 555G 37% /mnt > 1 [29/03 15:11:05] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 224G 647G 26% /mnt > 1 [29/03 15:41:38] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 670G 201G 77% /mnt > 1 [29/03 15:48:32] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 246G 626G 29% /mnt > 1 [29/03 15:48:36] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 313G 559G 36% /mnt > 1 [29/03 15:48:37] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 396G 475G 46% /mnt > 1 [29/03 15:48:37] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 615G 256G 71% /mnt > 1 [29/03 15:48:39] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 671G 201G 77% /mnt > 1 [29/03 15:48:40] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 671G 201G 77% /mnt > 1 [29/03 15:48:40] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 215G 656G 25% /mnt > 1 [29/03 15:48:41] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 334G 538G 39% /mnt > 1 [29/03 15:48:42] >> df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md5 1.3T 1.2T 113G 92% /data/mirror > /dev/sda1 917G 522G 349G 60% /mnt > 1 [29/03 15:48:43] >> > -- 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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