[Xen-users] Accessing SSD disks on VM

[Lloyd Dizon <thecarrionkind@xxxxxxxxx>]

Hi,
Do you have suggestions on how to properly access SSD disks?
Currently I have a RAID0 on two SSD disks, accessible as /dev/md0.
md0 is used as a PV with LVM, on which I have a VG and a LV.
The LV is seen as xvda by the VM. I am using the whole LV as a root
device for the VM (no partitions).

I am seeing up to 25% less performance on the VM when doing IO tests
(not sure if I am doing the correct way to test IO).
Do you have any suggestions if I can do this configuration better.

Thanks.
Lloyd


IO tests with hdparm:
Avg. cached reads xvda: 2586.68 MB/s
Avg. cached reads md0: 2654.68 MB/s
Difference (cached reads) entre xvda et md0: 97% -> 3% moins rapide sur VM
---
Avg. buffered reads xvda: 357.67 MB/s
Avg. buffered reads md0: 419.67 MB/s
Difference (buffered read) entre xvda et md0: 85% -> 15% moins rapide sur VM

IO tests with dd:
vm:~ # time dd if=/dev/zero of=/var/tmp/zero.txt bs=1k count=10485760
10485760+0 records in
10485760+0 records out
10737418240 bytes (11 GB) copied, 118.399 s, 90.7 MB/s

xen:/mnt/ioaccel_vm/var/tmp # time dd if=/dev/zero of=./zero-phy.txt
bs=1k count=10485760
10485760+0 records in
10485760+0 records out
10737418240 bytes (11 GB) copied, 90.4089 s, 119 MB/s

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