From: "Yanni M." <gianni.milo22@gmail.com>
To: Proxmox VE user list <pve-user@lists.proxmox.com>
Subject: Re: [PVE-User] ZFS Disk Usage unexpected high
Date: Mon, 5 Apr 2021 10:54:40 +0100 [thread overview]
Message-ID: <CACzVk9W=7Dbst916wMnFuJuMjS17zk0d4GPT8MNd7T1Gb4myWw@mail.gmail.com> (raw)
In-Reply-To: <7e9d1358dcb12b288e884547553e39b4@konsec.com>
This is a common issue on raidz based pools. Assuming 4k sectors
(ashift=12) and zvol with 8K volblocksize, each 8K (2-sector) block uses a
single sector (4k) of parity. So 15TB of 8KB blocks (default
volblocksize=8k) takes up at least 22.5TB space on disk (including parity).
You will use less parity by increasing the volblock size (e.g.
volblocksize=32k, or the default recordsize=128k for filesystems) in
exchange of a possible lower performance. Another solution would be using a
pool of striped mirrors (RAID10). This problem does not exist in such pools
(as there are no parity blocks used).
On Mon, 5 Apr 2021 at 09:23, Konold, Martin <martin.konold@konsec.com>
wrote:
>
> Hi,
>
> I set up a single VM which currently used 15TB of data.
> /dev/sdb is technically a ZFS volume on the Proxmox Host.
>
> [root@vm ~]# df -h /data
> Filesystem Size Used Avail Use% Mounted on
> /dev/sdb 40T 15T 25T 37% /data
> [root@vm ~]# du -s /data/
> 14874345100 /data/
>
> [root@host /]# zfs list zfs01/PVE-BE/vm-1-disk-1
> NAME USED AVAIL REFER MOUNTPOINT
> zfs01/PVE-BE/vm-1-disk-1 31.5T 5.82T 31.5T -
>
> Why is the usage on the host about twice as large as within the vm?
> (Yes, I have given fstrim and discard a try).
>
> --
> Regards
> ppa. Martin Konold
>
> --
> Martin Konold - Prokurist, CTO
> KONSEC GmbH - make things real
> Amtsgericht Stuttgart, HRB 23690
> Geschäftsführer: Andreas Mack
> Im Köller 3, 70794 Filderstadt, Germany
> <https://www.google.com/maps/search/Im+K%C3%B6ller+3,+70794+Filderstadt,+Germany?entry=gmail&source=g>
>
> _______________________________________________
> pve-user mailing list
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>
next prev parent reply other threads:[~2021-04-05 9:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-05 8:22 Konold, Martin
2021-04-05 9:54 ` Yanni M. [this message]
2021-04-06 7:41 ` Maximilian Hill
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