Article ID: 118600, created on Nov 13, 2013, last review on Apr 3, 2015

  • Applies to:
  • Virtuozzo 6.0


  1. A large amount of errors from pfcache daemon can be found in /var/log/messages:

    Nov 10 04:02:11 pcs1 pfcached[8799]: Claiming 10.20GB more than pfcache size - 9.84GB
    Nov 10 04:02:11 pcs1 pfcached[8799]: Trying to purge full pfcache...
    [root@pcs1 ~]# grep "Trying to purge full pfcache" /var/log/messages | wc -l
  2. A high IO occurs for pfcache:

    ~]# iotop -p 2689
    Total DISK READ: 0.00 B/s | Total DISK WRITE: 7.82 M/s
    TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND                                                                                       
    2689 be/3 root        0.00 B/s    0.00 B/s  0.00 % 81.05 % [jbd2/ploop61786]
    ~]# ploop list -a |grep ploop61786
    ploop61786   /vz/pfcache.hdd/root.hdd /vz/pfcache


These messages mean that there are requests to cache more bytes than available in the entire pfcache. The default pfcache size limit is 10GB.

High IO will appear when pfcache is lack of space.

    ~]# ploop info /vz/pfcache.hdd/DiskDescriptor.xml
    resource           Size            Used
    1k-blocks          10319140        10302752
    inodes             655360          17536


Check that there's enough space on /vz partition:

[root@pcs1 ~]# df -h /vz
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              99G   32G   63G  34% /vz

Resize the pfcache ploop device to some larger value:

    [root@pcs1 ~]# ploop resize -s 20G /vz/pfcache.hdd/DiskDescriptor.xml
    Storing /vz/pfcache.hdd/DiskDescriptor.xml.tmp
    Growing dev=/dev/ploop34134 size=20971520 sectors (new size=41943040)
    Update GPT partition to 41943040sec (512)
    update partition table start=1048576 length=21473770496
    Running: /usr/libexec/resize2fs -p /dev/ploop34134p1 20967424k
    resize2fs 1.42.3 (14-May-2012)
    Filesystem at /dev/ploop34134p1 is mounted on /vz/pfcache; on-line resizing required
    old_desc_blocks = 1, new_desc_blocks = 2
    The filesystem on /dev/ploop34134p1 is now 5241856 blocks long

Pfcache auto-resize feature will be implemented in future versions of PCS in scope of PSBM-23467

Search Words

more than pfcache size



Trying to purge full pfcache

high io wait jbd2 ploop

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