2010/9/9 Marcel Lohmann <marcel.lohmann@xxxxxxxxxxxxxx>: > 2010/9/8 Zhu Yanhai <zhu.yanhai@xxxxxxxxx>: >> Hi, >> Have you ever tried with 'mkfs.btrfs -m single /dev/xxxx'? >> As you had a RAID1 based on LVM, you don't have to keep >> the default duplicated metadata profile in Btrfs. >> >> -zyh >> >> 2010/9/8 Marcel Lohmann <marcel.lohmann@xxxxxxxxxxxxxx>: >>> In that complete logical volume I created a btrfs partition. And >>> btrfs-show displays 130GB space. Fine. > >>> to give me the actual numbers. And that tells me: >>> Data: total=23.97GB, used=23.97GB >>> Metadata: total=53.01GB, used=33.98GB >>> System: total=12.00MB, used=16.00KB > > No, I did not try this. I just created it with the defaults > "mkfs.btrfs /dev/mapper/somelogicalvolume". Isn't "-m single" the > default? No, it's not by default. Btrfs will write two copies of the Metadata into disk by default, with only one copy of Data -- something similar with RAID1, but not the same. Anyway, you don't need this, since you already have a standard RAID1 array setup by LVM. '-m single' makes Btrfs write exactly one copy of Metadata, instead of two by default. > So is it right that btrfs "knows" that it is running on a RAID and > changes it's behavior? Why? Normally a FS does not care about the > underlaying (hidden) disk array. No, it doesn't know. > But if it is neccessary to "drop" that duplicate metadata, how can I > arrange this afterwards. And if it is done, then I would have reduced > the Metadata size, but will there really be more space for Data? Where > is the remaining space from 77 GB to 130 GB? 53 * 2 + 24 = 130. The size of Metadata reported by "btrfs filesystem df" is 53GB, however it occupies 53 * 2 = 106GB on 'disk' physically. So yes, there will be more space for Data. > > Maybe I was pointing it the wrong way, sorry. I created a mdadm > software RAID1 and on that is a LVM. I did not use btrfs to span over > two disks. The md RAID with LVS was there before and I couldn't change > this. > This is why I have no btrfs-RAID but a md-RAID. > > Marcel > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
