Timeline for How full is my ZFS pool? (not sure how to read command output)
Current License: CC BY-SA 3.0
6 events
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| Dec 19, 2017 at 19:43 | comment | added | Peter |
Stilez - I feel that zdb is a developer tool, not an admin tool. I've been administering ZFS pools (up to 150TB) for eight years, under Solaris, Linux and FreeBSD, and I've only used zdb once (under FreeBSD to make sure my settings were accepted). I'm sorry, but I don't understand the ZFS internals enough to help you translate the zdb output to match the zpool or zfs output. What I do know is that the zpool and zfs commands provide correct output, and that their values should be very close with mirrors (not so close with RAID-Z1/2/3, due to what they actually look at).
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| Dec 19, 2017 at 3:53 | comment | added | Stilez | Peter - you may not mean it but your comment above feels as if it comes over as "its job is to help administrators and I'm sure it can help them, but you would need in depth knowledge to understand it and I don't know if you would understand it so this is clearly knowledge you shouldn't worry yourself over, leave it to a sysadmin and go back to Lego". You might not mean it as incredibly condescending but it is. If you know, please explain. If not, your comment hasn't added anything anyway. My question is how zdb's blocks , size x refs info reconciles to zpool's physical/logical volume size | |
| Dec 19, 2017 at 3:48 | comment | added | Stilez | I'm not that bad at in-depth :) zdb listed block count by size, physical count and logical reference in the pool. Total blocks x size (x refcount) should roughly be close to physical+logical space used. Why don't either of these even approximately match the actual used space in the pool? By a rather large factor (many times over). The space used should, probably, map onto blocks one way or another. So how do the 2 figures reconcile? Seems a very clear question. If they don't, what accounts for the difference and why isn't that amount of TB somewhere in the blocks allocated/referenced? | |
| Dec 18, 2017 at 17:07 | comment | added | Peter |
The purpose of the zpool and zfs commands is to allow the administrator/user to make changes and get status information. The purpose of the zdb command is to provide an view of the inner workings of the file-system. While I'm sure that the zdb command can be used to provide information on the available space in the pool/file-system, it would require an in-depth understanding of the ZFS structures to know that you're requesting/receiving the correct information, and to know how to interpret the information you receive.
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| Dec 17, 2017 at 8:11 | comment | added | Stilez | But how do these two outputs reconcile? Why are the zbd outputs so different? | |
| Dec 16, 2017 at 16:22 | history | answered | Peter | CC BY-SA 3.0 |