On Sat, Sep 29, 2012 at 12:02:23AM +0600, Roman Mamedov wrote:

On Fri, 28 Sep 2012 18:44:07 +0200
Goffredo Baroncelli [off-list ref] wrote:

quoted

This means that the ration of space physically allocated on the disk and 
the space available is 7GB/10GB = 0.7 . So on 135GB of disk, only 94GB 
are available.

You assume metadata allocation will always grow linearly with data, which is
not true. So in my opinion it is not a good estimate.

   No, but it's the best model we have right now. (And probably about
the best model we will have, without knowledge of the future
intentions of the user). Without inlining file data, the metadata is
dominated by checksums, which is a linear relationship (approx
1000:1). With inlining file data, metadata is probably dominated by
inline data; assuming the ratio of small-to-large files on the FS
remains unchanged in future, a linear relationship also applies. For
general usage, I'm happy to assume that the current ratio of data to
metadata will remain largely unchanged over the lifetime of the FS.

quoted

quoted

Why use underscores instead of spaces?

Simplify the parsing in scripts

I think it looks awkward and is not warranted since this is a primarily
user-facing utility. Also none of the other similar tools shy from having
spaces anywhere they need to, e.g.

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Wed May 25 00:07:38 2011
     Raid Level : raid5
     Array Size : 3907003136 (3726.01 GiB 4000.77 GB)
  Used Dev Size : 976750784 (931.50 GiB 1000.19 GB)
   Raid Devices : 5
  Total Devices : 5
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Fri Sep 28 21:20:51 2012
          State : active 
 Active Devices : 5
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : avdeb:0  (local to host avdeb)
           UUID : b99961fb:ed1f76c8:ec2dad31:6db45332
         Events : 14254

    Number   Major   Minor   RaidDevice State
       7       8       17        0      active sync   /dev/sdb1
       6       8       33        1      active sync   /dev/sdc1
       3       8       65        2      active sync   /dev/sde1
       4       8       49        3      active sync   /dev/sdd1
       5       8       81        4      active sync   /dev/sdf1

# lvdisplay 
  --- Logical volume ---
  LV Path                /dev/alpha/lv1
  LV Name                lv1
  VG Name                alpha
  LV UUID                HP19fU-oMhM-sdqN-yFWa-N3Rs-ktBw-21GSD2
  LV Write Access        read/write
  LV Creation host, time , 
  LV Status              available
  # open                 0
  LV Size                3.52 TiB
  Current LE             115431
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     4096
  Block device           252:0

   ... and I've always found those hard to deal with in scripts. :)

   (But they do have "plumbing" options, to use the git terminology,
so I'd be happy with having a parsable output option).

   Hugo.

-- 
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