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Ketan Maheshwari
Asked: 2016-08-15 15:57:37 +0800 CST

Why does `zfs list` and `zpool list` report very different sizes for my raidz2 pools?

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I have a ZFS server with 8 zpools. Each pool is 12 6TB disks in a 10+2 RAIDZ configuration. So, each pool has a raw storage space of 12*6=72 TB and usable space of 10*6=60 TB. However, I see different results when I query it using zfs list vs. using zpool list as below:

# zfs list
NAME     USED  AVAIL  REFER  MOUNTPOINT
intp1    631K  48.0T   219K  /intp1
intp2    631K  48.0T   219K  /intp2
intp3    631K  48.0T   219K  /intp3
jbodp4   631K  48.0T   219K  /jbodp4

# zpool list
NAME     SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
intp1     65T  1.02M  65.0T         -     0%     0%  1.00x  ONLINE  -
intp2     65T  1020K  65.0T         -     0%     0%  1.00x  ONLINE  -
intp3     65T  1.02M  65.0T         -     0%     0%  1.00x  ONLINE  -
jbodp4    65T  1.02M  65.0T         -     0%     0%  1.00x  ONLINE  -

Could someone help me understand why is this discrepancy?

zfs zfsonlinux

1 Answers

  1. Best Answer

    I'm surprised you have such a large setup. Did you build this array? This is potentially a bad arrangement for performance due to the pool design.

    Either way, the zpool man page explains this. zfs list will show your usable space. The zpool list shows parity space as storage space. 

       used                Amount of storage space used within the pool.

   The  space  usage properties report actual physical space available to the storage pool. The physical
   space can be different from the total amount of space that any contained datasets can  actually  use.
   The  amount  of  space used in a raidz configuration depends on the characteristics of the data being
   written. In addition, ZFS reserves some space for internal accounting that the zfs(8)  command  takes
   into  account, but the zpool command does not. For non-full pools of a reasonable size, these effects
   should be invisible. For small pools, or pools that are close to being completely  full,  these  dis-
   crepancies may become more noticeable.
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