Hi btrfs list,
I am looking for some counsel regarding how to best (and most safely)
utilize extra space on my btrfs installation. I set up a btrfs
installation about 6 months ago. I wanted to test the system while
waiting for mainline acceptance and support. The machine being used has
13 1Tb drives. 12 as a btrfs collection (stripe data, mirror metadata)
and 1 ext4 as a system drive. We are running kernel 3.2.0-rc4. I know
that it is not the latest, but it has been extremely stable for our
needs. Currently the system holds backup files. 2 other filesystems
are nfs mounts on the machine and backups are created by rsyncing these
mounts onto btrfs. The btrfs copies are also snapshotted, so 2 copies
exist of backup data. I have added the output of btrfs fi show and
btrfs fi df below so you can see the layout, as well as a standard df
-h. As will be readily apparent, my nfs disks are approaching storage
limits. Due to financial constraints I must use the space on the btrfs
system for nfs storage. My first thought is to take 3 or 4 T as a
subvol and export it as nfs. I have not heard of anyone else exporting
btrfs, is it possible? Next idea is to split several drives off the
btrfs system. I have removed drives and replaced them as experiments
with the fs but had much less data on them when I was trying that. I
have read many times on the list, about size issues with btrfs, and
filesystems reporting full when they were far from it. As my system has
been very stable just r/w data and creating and removing subvols, I am
reluctant to change the disk layout, but we will do what we have to.
Also, if I split disks out they could be mirrored, like our other nfs
systems. However, I can stand a small amount of filesystem downtime.
Therefore to maximize space we may look at not mirroring the segment but
just mount a backup snapshot if a main fs drive goes out. Final
question is what about backup space. Regardless of how I structure the
new storage segment, it will need to be backed up with the rest of the
system. Once again, I am between maximizing available storage and
leaving breathing room for btrfs. As I currently backup over 4T on
btrfs perhaps I should only allocate 2T for new storage thus creating 2T
storage, 6+T backup and 1+T breathing room. I am not in a panic
situation, but I will need to create the new storage over the next 2
months. I would really appreciate any feed back and comments concerning
this operation. Thanks in advance.
Jim Maloney
[root@btrfs ~]# btrfs fi show
failed to read /dev/sr0
Label: none uuid: c21f1221-a224-4ba4-92e5-cdea0fa6d0f9
Total devices 12 FS bytes used 4.62TB
devid 12 size 930.99GB used 414.75GB path /dev/sdl
devid 11 size 930.99GB used 414.75GB path /dev/sdk
devid 10 size 930.99GB used 414.99GB path /dev/sdj
devid 9 size 930.99GB used 414.99GB path /dev/sdi
devid 5 size 930.99GB used 414.99GB path /dev/sde
devid 2 size 930.99GB used 414.74GB path /dev/sdb
devid 1 size 930.99GB used 414.76GB path /dev/sda
devid 7 size 930.99GB used 414.99GB path /dev/sdg
devid 3 size 930.99GB used 414.74GB path /dev/sdc
devid 4 size 930.99GB used 414.74GB path /dev/sdd
devid 6 size 930.99GB used 414.99GB path /dev/sdf
devid 8 size 930.99GB used 414.99GB path /dev/sdh
[root@btrfs ~]# btrfs fi df /btrfs
Data, RAID0: total=4.54TB, used=4.50TB
Data: total=8.00MB, used=0.00
System, RAID1: total=8.00MB, used=324.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=164.25GB, used=122.97GB
Metadata: total=8.00MB, used=0.00
[root@btrfs ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sdm2 196G 49G 138G 26% /
tmpfs 16G 0 16G 0% /dev/shm
/dev/sdm1 2.0G 137M 1.8G 8% /boot
/dev/sdm5 1.2T 19G 1.1T 2% /var
/dev/sda 11T 4.8T 6.1T 44% /btrfs
10.2.0.42:/data/sites
2.6T 2.1T 388G 85% /nfs2/data/sites
10.2.0.40:/data/sites
2.6T 2.3T 218G 92% /nfs1/data/sites
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