[mythtv-users] MythTV Hardware Upgrade Questions

Zuriel elpinkus at yahoo.com
Wed Jun 29 00:20:53 UTC 2011


> But seriously, I am interested in how this affects your performance as

> I have a similar issue.  I am tempted to go with a USB stick or SSD
> for the database, but I am leery of putting that on something that has
> a limited amount or read/write cycles (although that limit may be much
> higher than what I would encounter, but I imagine the db gets a lot of
> writes on a daily basis).

An SSD does wear levelling. Instead of overwriting the same flash pages again and again and again, every time the SSD controller is told to write to a certain logical sector it will write to a new area of flash and lie about it to the OS.

With wear levelling and TRIM working properly on a modern SSD, you really only have to track the amount of data written to the SSD because flash won't actually be re-used until all of the flash has been used once. Even with tons of write operations happening, you aren't going to wear out an SSD in a reasonable number of years unless you're writing hundreds of gigabytes to it per day.

Keep in mind that the SSD uses free space for wear levelling and to prevent performance-reducing fragmentation. And it can't be defragmented by any OS-level tool due to the aforementioned lying about where data is located. A fragmented SSD has to be imaged onto a different drive, secure erased (not just formatted or even zeroed, you need to use the secure erase commands to instruct the SSD controller to perform the erase because it's the only thing that knows what's really going on with the flash) and then imaged back.

Remember: a half empty SSD is a happy SSD. :P
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