[PVE-User] Understanding write caching in proxmox

Chris Murray chrismurray84 at gmail.com
Tue Feb 4 15:58:06 CET 2014

I'm not sure I get a chance to specify?

root at pm02:/# mount -l | grep 231 on /mnt/pve/foxpool type nfs (rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=,mountvers=3,mountport=918,mountproto=udp,local_lock=none,addr=

It was set up using the web interface, where I can't see an option for this.

NFS client certainly feels asynchronous to me. Suppose I "sar -n DEV 1 | grep eth0" while I observe this 'buffering' effect ... I see next to no activity until the instant that "zpool iostat" does. i.e. the proxmox host is holding onto data and choosing to flush it at a later stage.

Thanks again,

-----Original Message-----
From: Pongrácz István [mailto:pongracz.istvan at gmail.com] 
Sent: 04 February 2014 14:39
To: Chris Murray; Alexandre DERUMIER
Cc: pve-user pve.proxmox.com
Subject: Re: [PVE-User] Understanding write caching in proxmox

How about your NFS setup? Sync, async?


----------------eredeti üzenet-----------------
Feladó: "Chris Murray" chrismurray84 at gmail.com
Címzett: "Alexandre DERUMIER" aderumier at odiso.com
CC: pve-user at pve.proxmox.com
Dátum: Tue, 4 Feb 2014 14:14:51 -0000
> Sorry, I might have misled you with my question. It might have the 
> appearance of another general and possibly quite common one.
> My troubleshooting was performed on the proxmox *host*, therefore I 
> was under the impression that cache=[whatever] wouldn't make a 
> difference since that's a property of a virtual machine disk.
> For the *VM*, I'm using writethrough .. however I'm observing exactly 
> what you explained for 'none' or 'writeback'. My VM is Windows Server 
> 2008 R2, and I'm using sdelete to fill it with data. 'sdelete -z' 
> won't appear on the 'zpool iostat' for quite some time, while the 
> cached figure on the proxmox host increases. That's despite the disk being set to writethrough.
> Apologies if I'm not being clear.

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