Laptop with SSD with a VM on an external drive

I heard that running a VM on a laptop with a SSD is bad because it does a lot of system calls and therefore a lot of writes (which a lot of system calls = bad for SSD drives for some reason).

So if I were to have my VM files all on an external drive (that isn't flash storage) will this solve the problem/be better?

 

Honestly, i wouldn't worry about it. Sure SSDs have a finite amount of writes, but you have to be literally abusing the drive to wear it prematurely.

 

Would 'hosting' the VM on an external drive solve the writing issue though?

 

Honestly, since i don't run VMs, i don't know. However, there is no "problem" to begin with. Some people baby their SSDs and worry too much about writes.

 

Why wouldn't it be a problem though? Including if I'm using multiple VMs in the long run?

 

Simply put, you will replace the drive long before the writes become a problem. To have a real chance at killing a consumer SSD, you have to put a server like load on it which isn't what you're gonna do.

The question you're asking is akin to asking why installing the primary OS on the SSD is a bad idea because the OS will make a lot of small writes to the SSD. A SSD is meant to be used and i'm sure a lot of people would rather have their VMs on a SSD to speed things up. I don't have the link right now, but some people are abusing their SSDs on purpose and according to their testing, the SSD will last much longer than the 5 years advertised by the manufacturers and if you need to run VMs, it's likely that you'll upgrade to a new computer with a larger faster and cheaper SSD within that 5 years period. Even the extra writes from the VMs won't be enough to kill the SSD prematurely.

In the end, the decision is up to you, but you're worrying for nothing.

 

And to state the obvious; the big performance hit running a VM on an external drive will be even more noticable if your main OS is on a SSD. And if you run more than one VM at once it just gets worse.

 

Agree with Tijo on most of this.

I have about 12 VMs (of which 3 are in perpetual use). Due to size issues, I keep them on my XTs (which provide plenty of performance due to the SSD read cache). However, if you can spare the size, shouldn't be too much of an issue keeping them on the SSD.

If it makes you feel any better, you can use things that read the S.M.A.R.T. values or a utility like SSDlife to keep an eye on writes for the drive.

In addressing your actual post, where did you see such info? I would question the source.

Also, if that source said system calls equates to a writes to your SSD, then totally discount that information. A system call to the OS is a read from an instruction which may have to issue an SSD read (to load a library for example). Most system calls do not cause WRITEs to an SSD.

However, if the system call directly told the OS to write something to the VMs file system, or some interaction caused a context switch that the virtual memory flushed some address space to disk, then an SSD write might occur. At that point, since this all takes place within your VM software, it is up to that process to decide when those changed actually get written to disk.

HTH

 

What if I want my drive to 'last' for over 3-5 years? Would it matter still?

 

What we're saying is that even when running VMs the drive will last more than 5 years.

 

what do you use these for? i'm new to VMs and why ppl use them..

 

^^^

For work purposes I need different environments / setups / OSs, etc. to write and test software. At one point had a couple of machines w/ easy swap HDD bays and different configs stored on a library of HDDs. When technology advanced enough that VMs ran with acceptable performance, all that hardware disappeared replaced by VMs.