[Qemu-devel] Re: SSD Trim Support- Current State?

[Nicolas Sebrecht <nsebrecht@piing.fr>]

The 17/03/13, d hee wrote:

> What is the current state of SSD Trim/Discard support  for a Qemu/KVM guests? 
> 
> I run a Qemi/ KVM host wtih these kvm guests...they are all Linux os's and use raw images: 1) 20 gig Linux web-server 2) Subsonic music streaming server for my Android phone 3) Postfix server for automated emails 4) Linux guest for sandbox for testing. All of this is on my on personal system as a hobby and not a a business "production" system. If I run them off a ssd drive without the trim support, will I see performance impacted as the guest blocks slowly fill up without being marked for reuse?

Depends of the SSD you have and the use you make of it. For recent
enough SSD, TRIM support is no more required as firmwares better manage
blocks and pages than in the first days of SSD.

Unless you use your SSD for big rewrites every day, I bet you won't have
to enable TRIM.

Also, If you still want TRIM enabled I think there is no need for
QEMU/KVM to support TRIM as you use RAW format. This is the job of your
guests.

What would make high preformance degradation is not having blocks
aligned.

-- 
Nicolas Sebrecht