ZFS cheatsheet

• Reparieren von defktem ZFS

• Wichtige ZFS-Patches: 127729-07 (x86) / 127728-06 (SPARC)
• ZFS Best Practices Guide http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
• ZFS FAQ bei Opensolaris.org http://www.opensolaris.org/os/community/zfs/faq/

ZFS Tuning

Eine gefühlte Langsamkeit auf Systemen mit ZFS kommt vom sehr großen Cachehunger. Den kann man eingrenzen: Erstmal schauen, was phase ist:

lollypop@wirefall:~# echo "::kmastat ! grep Total" |mdb -k
Total [hat_memload]                             13508608B 309323764     0
Total [kmem_msb]                                24010752B   1509706     0
Total [kmem_va]                                660340736B    140448     0
Total [kmem_default]                           690409472B 1416078794     0
Total [kmem_io_64G]                             34619392B      8456     0
Total [kmem_io_4G]                                 16384B        92     0
Total [kmem_io_2G]                                 24576B        62     0
Total [bp_map]                                   1048576B    234488     0
Total [umem_np]                                   786432B       976     0
Total [id32]                                        4096B      2620     0
Total [zfs_file_data_buf]                      1471275008B   1326646     0
Total [segkp]                                     589824B    192886     0
Total [ip_minor_arena_sa]                             64B     13332     0
Total [ip_minor_arena_la]                            192B     45183     0
Total [spdsock]                                       64B         1     0
Total [namefs_inodes]                                 64B        24     0
lollypop@wirefall:~#  echo "::memstat" | mdb -k
Page Summary                Pages                MB  %Tot
------------     ----------------  ----------------  ----
Kernel                     255013               996   24%
ZFS File Data              359196              1403   34%
Anon                       346538              1353   33%
Exec and libs               33948               132    3%
Page cache                   4836                18    0%
Free (cachelist)            22086                86    2%
Free (freelist)             23420                91    2%

Total                     1045037              4082
Physical                  1045036              4082

Oder nur ZFS

echo "::memstat ! egrep '(Page Summary|-----|ZFS)'"| mdb -k

Ausgeben aller ARC-Parameter:

lollypop@wirefall:~#  echo "::arc -m" | mdb -k
hits                      =  80839319
misses                    =   3717788
demand_data_hits          =   4127150
demand_data_misses        =     51589
demand_metadata_hits      =   9467792
demand_metadata_misses    =   2125852
prefetch_data_hits        =    127941
prefetch_data_misses      =    596238
prefetch_metadata_hits    =  67116436
prefetch_metadata_misses  =    944109
mru_hits                  =   2031248
mru_ghost_hits            =   1906199
mfu_hits                  =  78514880
mfu_ghost_hits            =    993236
deleted                   =    880714
recycle_miss              =   1381210
mutex_miss                =       197
evict_skip                =  38573528
evict_l2_cached           =         0
evict_l2_eligible         = 94658370048
evict_l2_ineligible       = 8946457600
hash_elements             =     79571
hash_elements_max         =     82328
hash_collisions           =   3005774
hash_chains               =     22460
hash_chain_max            =         8
p                         =        64 MB
c                         =       512 MB
c_min                     =       127 MB
c_max                     =       512 MB
size                      =       512 MB
hdr_size                  =  14825736
data_size                 = 468982784
other_size                =  53480992
l2_hits                   =         0
l2_misses                 =         0
l2_feeds                  =         0
l2_rw_clash               =         0
l2_read_bytes             =         0
l2_write_bytes            =         0
l2_writes_sent            =         0
l2_writes_done            =         0
l2_writes_error           =         0
l2_writes_hdr_miss        =         0
l2_evict_lock_retry       =         0
l2_evict_reading          =         0
l2_free_on_write          =         0
l2_abort_lowmem           =         0
l2_cksum_bad              =         0
l2_io_error               =         0
l2_size                   =         0
l2_hdr_size               =         0
memory_throttle_count     =         0
arc_no_grow               =         0
arc_tempreserve           =         0 MB
arc_meta_used             =       150 MB
arc_meta_limit            =       128 MB
arc_meta_max              =       313 MB

Man kann sich auch alle Parameter ausgeben lassen, die für ZFS gesetzt sind mit:

 # echo ::zfs_params | mdb -k
arc_reduce_dnlc_percent = 0x3
zfs_arc_max = 0x100000000
zfs_arc_min = 0x0
arc_shrink_shift = 0x5
zfs_mdcomp_disable = 0x0
zfs_prefetch_disable = 0x0
zfetch_max_streams = 0x8
zfetch_min_sec_reap = 0x2
zfetch_block_cap = 0x100
zfetch_array_rd_sz = 0x100000
zfs_default_bs = 0x9
zfs_default_ibs = 0xe
...
# echo "::arc -a" | mdb -k
hits                      =    592730
misses                    =      5095
demand_data_hits          =         0
demand_data_misses        =         0
demand_metadata_hits      =    592719
demand_metadata_misses    =      4866
prefetch_data_hits        =         0
prefetch_data_misses      =         0
...

Setzen von Kernelparametern geht auch online mit:

# echo zfs_arc_max/Z100000000 | mdb -kw
zfs_arc_max:    <old value>             =       0x100000000

Das setzt den zfs_arc_max auf 4GB = 0x100000000

Limitieren des ARC Cache

In der /etc/system einfach: set zfs:zfs_arc_max = <Number of bytes>

Siehe auch Limiting the ARC Cache

ZFS Platzverbrauch besser anzeigen

$ zfs list -o space
NAME               AVAIL   USED  USEDSNAP  USEDDS  USEDREFRESERV  USEDCHILD
rpool              25.4G  7.79G         0     64K              0      7.79G
rpool/ROOT         25.4G  6.29G         0     18K              0      6.29G
rpool/ROOT/snv_98  25.4G  6.29G         0   6.29G              0          0
rpool/dump         25.4G  1.00G         0   1.00G              0          0
rpool/export       25.4G    38K         0     20K              0        18K
rpool/export/home  25.4G    18K         0     18K              0          0
rpool/swap         25.8G   512M         0    111M           401M          0

Wenn zfs list -o space als shortcut noch nicht zur Verfügung steht, geht meist:

$ zfs list -o name,avail,used,usedsnap,usedds,usedrefreserv,usedchild -t filesystem,volume