UFS zfs vs ufs and how to keep more of my disk space and avoid reboot hell

Hastur

Hastur

I have 5 usb external disks.
Desktop hp z240 8g ram i7 usb3 (got $90 from ebay because no vhs only display port for video but bought adapter to vga for cheap flat screen monitor I have)

Code: 
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ada0p2    222G    141G     63G    69%    /
devfs          1.0K      0B    1.0K     0%    /dev
/dev/ada0p1    260M    1.3M    259M     1%    /boot/efi
/dev/da2p2     5.3T    4.6T    215G    96%    /a
/dev/da1p1     3.5T    3.1T    112G    97%    /b
/dev/da3p1     4.4T    1.2T    2.8T    30%    /c
/dev/da0p1     3.5T    2.6T    669G    80%    /d
/dev/da4p1     7.3T    7.1T    134G    98%    /e

All are UFS save e which is NTFS mounted with NTFS-3g

1 How do I keep ufs from eating 100s of gigs on each ufs disk? example: /a above 5.3T but 4.6+0.215 T usable???
losing 500g?
2 If I move things around and 1 by 1 make all the disks 1 zpool, will I get better speed? It would seem I risk 1 disk nuking the whole virtual disk as a danger... is there a way to see if a disk is failing b4 such disaster? None are SSD save the os internal disk ada0
3 I remember I had 3 or 4 disks in zfs zpool a few years back and reboot would cause chaos. ZFS would not see disks. I even think I had given uuid of each disk to ZFS. It kinda scared me. Is this more stable now?
This made me go back to ufs.
 
tunefs(8)

Code: 
 -m minfree
           Specify the percentage of space held back  from    normal    users;
           the  minimum  free  space threshold.  The default value used is
           8%.  Note that lowering the threshold can adversely affect per-
           formance:

           •   Settings of 5% and less force space optimization to    always
           be  used  which will    greatly    increase the overhead for file
           writes.

           •   The file system's ability to    avoid  fragmentation  will  be
           reduced  when  the total free space,    including the reserve,
           drops below 15%.  As    free space approaches zero, throughput
           can degrade by up to    a factor of three over the performance
           obtained at a 10% threshold.

           If the value is raised above the     current  usage     level,     users
           will  be     unable    to allocate files until    enough files have been
           deleted to get under the    higher threshold.
 
VladiBG said:
tunefs(8)

Code: 
 -m minfree
           Specify the percentage of space held back  from    normal    users;
           the  minimum  free  space threshold.  The default value used is
           8%.  Note that lowering the threshold can adversely affect per-
           formance:

           •   Settings of 5% and less force space optimization to    always
           be  used  which will    greatly    increase the overhead for file
           writes.

           •   The file system's ability to    avoid  fragmentation  will  be
           reduced  when  the total free space,    including the reserve,
           drops below 15%.  As    free space approaches zero, throughput
           can degrade by up to    a factor of three over the performance
           obtained at a 10% threshold.

           If the value is raised above the     current  usage     level,     users
           will  be     unable    to allocate files until    enough files have been
           deleted to get under the    higher threshold.
Click to expand...
wow! thanks!
How does zfs compare?
 
You have compression, deduplication, snapshots and option of multiple copies so it's hard to compare but without them it waste more space.
 
VladiBG said:
tunefs(8)

Code: 
 -m minfree
           Specify the percentage of space held back  from    normal    users;
           the  minimum  free  space threshold.  The default value used is
           8%.  Note that lowering the threshold can adversely affect per-
           formance:

           •   Settings of 5% and less force space optimization to    always
           be  used  which will    greatly    increase the overhead for file
           writes.

           •   The file system's ability to    avoid  fragmentation  will  be
           reduced  when  the total free space,    including the reserve,
           drops below 15%.  As    free space approaches zero, throughput
           can degrade by up to    a factor of three over the performance
           obtained at a 10% threshold.

           If the value is raised above the     current  usage     level,     users
           will  be     unable    to allocate files until    enough files have been
           deleted to get under the    higher threshold.
Click to expand...
reading this total free space including 8% reserve, so 93% or so not 85 before performance degrades
 
The default minfree is designed to maintain adequate write performance as the disk approaches being full.

As you decrease the minfree, the more likely you are to see degraded write speeds. This may not matter if your disk contents are static.

If your data are amenable to compression, then you are going to like ZFS compression.

ZFS dedup has a performance cost that may be of concern. It's being worked on...
 
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