On Sep 14, 2007, at 8:16 AM, Łukasz wrote:
> I have a huge problem with space maps on thumper. Space maps takes
> over 3GB
> and write operations generates massive read operations.
> Before every spa sync phase zfs reads space maps from disk.
>
> I decided to turn on compression for pool ( only for pool, not
> filesystems ) and it helps.
> Now space maps, intent log, spa history are compressed.
How did you do that?
>
> Not I'm thinking about disabling checksums. All metadata are
> written in 2 copies,
> so when I have compression=on do I need checksums ?
They are separate things. If you want data integrity, then you need
to leave checksums enabled.
> Does zfs will try to read second block when zio_decompress_data
> will return error ?
>
> Is there other way to check space map compression ratio ?
> Now I'm using "#zdb -bb pool" but it takes hours.
#zdb -v <pool>
...
Traversing all blocks to verify checksums and verify nothing leaked ...
No leaks (block sum matches space maps exactly)
bp count: 103
bp logical: 1572352 avg: 15265
bp physical: 120832 avg: 1173
compression: 13.01
bp allocated: 296448 avg: 2878
compression: 5.30
SPA allocated: 296448 used: 0.00%
Blocks LSIZE PSIZE ASIZE avg comp %Total Type
3 12.0K 1.50K 4.50K 1.50K 8.00 1.55 deferred free
1 512 512 1.50K 1.50K 1.00 0.52 object
directory
2 1K 1K 3.00K 1.50K 1.00 1.04 object array
1 16K 1.50K 4.50K 4.50K 10.67 1.55 packed nvlist
- - - - - - - packed
nvlist size
5 528K 34.0K 102K 20.4K 15.53 35.23 bplist
- - - - - - - bplist header
- - - - - - - SPA space
map header
3 12.0K 1.50K 4.50K 1.50K 8.00 1.55 SPA space map
- - - - - - - ZIL intent log
51 816K 54.0K 113K 2.21K 15.11 38.86 DMU dnode
8 8K 4K 8.50K 1.06K 2.00 2.94 DMU objset
- - - - - - - DSL directory
4 2K 2K 6.00K 1.50K 1.00 2.07 DSL
directory child map
3 1.50K 1.50K 4.50K 1.50K 1.00 1.55 DSL dataset
snap map
4 2K 2K 6.00K 1.50K 1.00 2.07 DSL props
- - - - - - - DSL dataset
- - - - - - - ZFS znode
- - - - - - - ZFS ACL
6 3.00K 3.00K 3.00K 512 1.00 1.04 ZFS plain file
5 2.50K 2.50K 5.00K 1K 1.00 1.73 ZFS directory
3 1.50K 1.50K 3.00K 1K 1.00 1.04 ZFS master node
3 1.50K 1.50K 3.00K 1K 1.00 1.04 ZFS delete
queue
- - - - - - - zvol object
- - - - - - - zvol prop
- - - - - - - other uint8[]
- - - - - - - other uint64[]
- - - - - - - other ZAP
- - - - - - - persistent
error log
1 128K 6.00K 18.0K 18.0K 21.33 6.22 SPA history
- - - - - - - SPA history
offsets
- - - - - - - Pool properties
- - - - - - - DSL permissions
103 1.50M 118K 290K 2.81K 13.01 100.00 Total
capacity operations bandwidth ---- errors
----
description used avail read write read write read write
cksum
d 290K 24.4G 874 0 1023K 0 0
0 0
/dev/dsk/c1t1d0s7 290K 24.4G 874 0 1023K 0 0
0 0
fsh-hake#
eric
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