KVM guest performance on local SSD

[ahoi_]

Hello everybody,

I am just wondering, whether I can improve my guest's performance in any way:

I got a SSD-RAID (10) on `/dev/sda` which provides the local storage for my KVM guests.

A typical guest comes with these settings:




This is /etc/fstab

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mapper/vg00-root /               ext4    errors=remount-ro 0       1
# /boot was on /dev/vda1 during installation
UUID=2489960f-09a8-4d17-aa1a-7f2bd0e74541 /boot           ext2    defaults        0       2
/dev/mapper/vg00-swap_1 none            swap    sw              0       0

So in the "good old days" it was kinda "best practice" to set noatime to the filesystem to tell the OS not to write the date of last access.


My questions:

- Is this hint still "best practice" in times of SSDs?
- Which changes would you recommend in order to improve SSD speed? Of course I don't want an unsafe scenario.

 

[Stefan_R]

relatime is what's usually recommended if you do not need access time information. For SSDs it probably won't help speed, but depending on your workload *maybe* longevity. Considering you're running KVM guests however, you'd need to set that in the guest, not the host - the host only sees one file (per disk) anyway, or in case of LVM no files at all.

In more general terms, there's no magic "make it fast" flag for SSDs though. If there were, we'd have already applied it Some advanced tuning can of course always be done for special workloads, but that's something you need to figure out based on what you're doing with your VMs.

 

[ahoi_]

Alright. Thanks for your thoughts on that