Hi all,

On a testing cluster, I upgraded from Firefly to Giant.

Without changing anything, read performance on a RBD volume (in a VM)
has been divided by 4 !

With Firefly, in the VM (/dev/vda is a Virtio RBD device) :

hdparm -Tt /dev/vda
 
/dev/vda:
 Timing cached reads:   20568 MB in  1.99 seconds = 10314.48 MB/sec
 Timing buffered disk reads: 1190 MB in  3.00 seconds = 396.49 MB/sec


With Giant :

hdparm -Tt /dev/vda
 
/dev/vda:
 Timing cached reads:   20340 MB in  1.99 seconds = 10199.48 MB/sec
 Timing buffered disk reads: 318 MB in  3.00 seconds = 105.85 MB/sec


Write performance is the same than before, no change.

How can we explain this ?

Every system is running Debian Wheezy.

Thank you a lot.
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