[Info-vax] How do I assign a disk to a CPU?

[seasoned_geek]

On Friday, October 16, 2020 at 11:03:58 AM UTC-5, Stephen Hoffman wrote:
> 
> And if still on HDDs while pondering permuting preferred path, promote 
> pondering SSDs too. FC SAN Storage Controllers are fast, but HDDs are 
> HDDs and slow and there's only so much cache. 

In the PC world that hasn't exactly been my experience. SSDs are very fast with READ operations but duth sucketh with WRITE operations. They mask this with cache. When you are doing massive write operations, you need a spinning disk. 

Actually got forced into conducting that "experiment" on two different projects for the same client. Needed to build Qt from source looking for a magic build combination that would allow a single Debian to install and run on every YABU version they wanted to support. (Not as simple as that sounds.)

https://wiki.qt.io/Building_Qt_5_from_Git#Getting_the_source_code

In the same computer using a spinning drive no better than a 1TB Western Digital Blue, and several different Samsung 840 series SSDs the build time difference was about an hour. Performing all of the builds on a spinning disk shaved about a week off the project.

When faced with having to write thousands of tiny obj files the SSD just tossed up its hands. The on-disk cache backed up. The Linux OS disk cache backed up. Compilation halted. Basically it kept going out for cigarettes while it waited on the SSD. 

Part of me wonders what the time difference would have been had I used the 4TB WD Black drive I know have.

I'm not dissing the 840 line. I like them and have many of them. They are a good durable general purpose SSD. Pretty much every SSD I've ever encountered duth sucketh at massive builds. SSDs are fantastic with the I part of I/O. They are just near worthless when it comes to the O part. 

Maybe newer designs have "fixed" this problem, but I doubt it. 

Before there is any confusion, I started with one SSD. Lost patience with it. Used Terabyte's Image for Linux to make a bare metal backup. Swapped in an 840, laid down the image and went back to work. A few days later this duth sucketh too. Made another image. Swapped in a Blue drive. Laid image back down. Noticed a build time improvement of about an hour.

No. I didn't conduct this experiment in any scientific manner. I was just trying to make it to the end of a tunnel before the train came in.

As a result of my experience though, I never recommend an SSD for any high write system. Database tables (or RMS indexed files) that will have massive write operations I always recommend be placed on a good spinning disk due to the faster write operation. (Think order intake system during Black Friday sales or the H&R Block e-file central collection system during tax season for high write.)

Some day I will experiment with a hybrid drive.