ZFS Log Question

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Urumiko

Member
Apr 6, 2023
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Hi there,
I added 2 log drives to my pool using the command
zpool add DeadPool log sdb,sda.
My intent was that they be a mirror.
Will this command have the desired effect or did I need to mirror the drives first then add the mirror as a log drive?
 
Urumiko said:
Will this command have the desired effect
Click to expand...
You can check the actual configuration of your pool by running zpool status (and post the output here; please use [code]...[/code] for this.)

Guessing: no! The keyword "mirror" is missing --> zpool add DeadPool log mirror /dev/sda /dev/sdb

PS: are you sure that a SLOG will help you? In a lot of cases it does not do what the user thinks it does. (It helps only with SYNC writes; often it is oversized (max 10 seconds of incoming data) so it may be small; you need RAM for it...)
 
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UdoB said:
You can check the actual configuration of your pool by running zpool status (and post the output here; please use [code]...[/code] for this.)

Guessing: no! The keyword "mirror" is missing --> zpool add DeadPool log mirror /dev/sda /dev/sdb

PS: are you sure that a SLOG will help you? In a lot of cases it does not do what the user thinks it does. (It helps only with SYNC writes; often it is oversized (max 10 seconds of incoming data) so it may be small; you need RAM for it...)
Click to expand...

Ah, That's better Thank you for your help.
Yes it was more to avoid loss of data due to power/ram failure, but I'm also expecting it to help maintain write speeds for large copies?
I also have always sync turned on.
My current write tests are not going that fast (about 120mbps),
But I'm putting that down to doing an SMB copy over WIFI (despite my WIFI being gonnected at 2gig).
I have no atime set for my turnkey container. I trust that wont be impacting?

Pre advice:
Code: 
root@procmox:~# zpool status
  pool: DeadPool
 state: ONLINE
config:

        NAME                                 STATE     READ WRITE CKSUM
        DeadPool                             ONLINE       0     0     0
          raidz1-0                           ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NEJ  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NM3  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A1817Z  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NCF  ONLINE       0     0     0
        logs
          wwn-0x5e83a97059c03f9e             ONLINE       0     0     0
          wwn-0x500a075111424bdb             ONLINE       0     0     0

errors: No known data errors
root@procmox:~# zpool iostat DeadPool -v
                                       capacity     operations     bandwidth
pool                                 alloc   free   read  write   read  write
-----------------------------------  -----  -----  -----  -----  -----  -----
DeadPool                              107G  10.8T      0    183    701  29.7M
  raidz1-0                            107G  10.8T      0     64    521  17.0M
    ata-ST3000VN000-1HJ166_W6A18NEJ      -      -      0     16    132  4.26M
    ata-ST3000VN000-1HJ166_W6A18NM3      -      -      0     15    128  4.26M
    ata-ST3000VN000-1HJ166_W6A1817Z      -      -      0     16    136  4.26M
    ata-ST3000VN000-1HJ166_W6A18NCF      -      -      0     15    123  4.26M
logs                                     -      -      -      -      -      -
  wwn-0x5e83a97059c03f9e             54.3M   111G      0     59     90  6.35M
  wwn-0x500a075111424bdb             54.2M   119G      0     59     90  6.35M
-----------------------------------  -----  -----  -----  -----  -----  -----

Fixed:
Code: 
root@procmox:~# zpool remove DeadPool wwn-0x500a075111424bdb
root@procmox:~# zpool remove DeadPool wwn-0x5e83a97059c03f9e
root@procmox:~# zpool add DeadPool log mirror /dev/sda /dev/sdb
root@procmox:~# zpool status
  pool: DeadPool
 state: ONLINE
config:

        NAME                                 STATE     READ WRITE CKSUM
        DeadPool                             ONLINE       0     0     0
          raidz1-0                           ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NEJ  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NM3  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A1817Z  ONLINE       0     0     0
            ata-ST3000VN000-1HJ166_W6A18NCF  ONLINE       0     0     0
        logs
          mirror-3                           ONLINE       0     0     0
            sda                              ONLINE       0     0     0
            sdb                              ONLINE       0     0     0

errors: No known data errors
root@procmox:~# zpool iostat DeadPool -v
                                       capacity     operations     bandwidth
pool                                 alloc   free   read  write   read  write
-----------------------------------  -----  -----  -----  -----  -----  -----
DeadPool                              112G  10.8T      0     68  2.27K  16.9M
  raidz1-0                            112G  10.8T      0     67  1.78K  16.8M
    ata-ST3000VN000-1HJ166_W6A18NEJ      -      -      0     16    457  4.20M
    ata-ST3000VN000-1HJ166_W6A18NM3      -      -      0     16    454  4.20M
    ata-ST3000VN000-1HJ166_W6A1817Z      -      -      0     17    462  4.20M
    ata-ST3000VN000-1HJ166_W6A18NCF      -      -      0     16    449  4.20M
logs                                     -      -      -      -      -      -
  mirror-3                            103M   111G      1    217   114K  17.7M
    sda                                  -      -      0    108  56.9K  8.84M
    sdb                                  -      -      0    108  56.9K  8.84M
-----------------------------------  -----  -----  -----  -----  -----  -----
 
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