Monthly Archives: September 2022

Wrong, wrong, wrong

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I’m reading Fundamentals of Data Engineering: Plan and Build Robust Data Systems, wherein the authors say:

Data is stored in a table of relations (rows), and each relation contains multiple fields (columns); see Figure 5-7. Note that we use the terms column and field interchangeably throughout this book.

There are two mistakes. The first is that tables are relations, rows are tuples. The second is that a field is the intersection of a row and a column, columns and fields are different things.
I have to wonder what business the authors have publishing a book on data engineering while failing to know such basic things.

Resolving ZFS issue on ‘trick’

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I’m gonna follow these instructions to replace a disk in one of my ZFS arrays on my workstation ‘trick’. Have ordered myself a new 6TB Seagate Barracuda Hard Drive for $179. I hope nobody minds if I make a few notes for myself here…

-------------------
Mon Sep 12 19:24:53 [bash:5.0.17 jobs:0 error:0 time:179]
root@trick:/home/jj5
# zpool status data
  pool: data
 state: DEGRADED
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://zfsonlinux.org/msg/ZFS-8000-9P
  scan: scrub canceled on Mon Sep 12 19:24:53 2022
config:

        NAME                                     STATE     READ WRITE CKSUM
        data                                     DEGRADED     0     0     0
          mirror-0                               DEGRADED     0     0     0
            scsi-SATA_ST6000VN0041-2EL_ZA16N49H  DEGRADED 11.1K     0 54.6K  too many errors
            scsi-SATA_ST6000VN0041-2EL_ZA16N4ZH  ONLINE       0     0     0

errors: No known data errors
-------------------
Mon Sep 12 19:40:13 [bash:5.0.17 jobs:0 error:0 time:1099]
root@trick:/home/jj5
# zdb
data:
    version: 5000
    name: 'data'
    state: 0
    txg: 2685198
    pool_guid: 1339265133722772877
    errata: 0
    hostid: 727553668
    hostname: 'trick'
    com.delphix:has_per_vdev_zaps
    vdev_children: 1
    vdev_tree:
        type: 'root'
        id: 0
        guid: 1339265133722772877
        create_txg: 4
        children[0]:
            type: 'mirror'
            id: 0
            guid: 802431090802465148
            metaslab_array: 256
            metaslab_shift: 34
            ashift: 12
            asize: 6001160355840
            is_log: 0
            create_txg: 4
            com.delphix:vdev_zap_top: 129
            children[0]:
                type: 'disk'
                id: 0
                guid: 9301639020686187487
                path: '/dev/disk/by-id/scsi-SATA_ST6000VN0041-2EL_ZA16N49H-part1'
                devid: 'ata-ST6000VN0041-2EL11C_ZA16N49H-part1'
                phys_path: 'pci-0000:00:17.0-ata-3'
                whole_disk: 1
                DTL: 28906
                create_txg: 4
                com.delphix:vdev_zap_leaf: 130
                degraded: 1
                aux_state: 'err_exceeded'
            children[1]:
                type: 'disk'
                id: 1
                guid: 4734211194602915183
                path: '/dev/disk/by-id/scsi-SATA_ST6000VN0041-2EL_ZA16N4ZH-part1'
                devid: 'ata-ST6000VN0041-2EL11C_ZA16N4ZH-part1'
                phys_path: 'pci-0000:00:17.0-ata-4'
                whole_disk: 1
                DTL: 28905
                create_txg: 4
                com.delphix:vdev_zap_leaf: 131
    features_for_read:
        com.delphix:hole_birth
        com.delphix:embedded_data

I think the commands I’m gonna need are:

# zpool offline data 9301639020686187487
# zpool status data
# shutdown # and replace disk
# zpool replace data 9301639020686187487 /dev/disk/by-id/scsi-SATA_ST6000DM003-2CY1_WSB076SN
# zpool status data