2x USB thumbs in RAID0 as temporary download volume a good idea?

[jant90]

Hello,

I'm about to buy a nicely priced secondhand HP MicroServer N54L, install FreeNAS on it and install 5x 3TB HDD's (in RAIDZ) to act as a mediaserver. I want to run FreeNAS off a 16GB SanDisk Cruzer Ultra fit.

The server will do automatic usenet downloads using SABnzbd and a habit I always followed was using separate hard drives for downloading and extracting to keep the load on the drives down as much as possible (no concurrent read and write on the drive), also this allows the drives to idle and spin down more often.

So in order to realize this I want to add 2x 32GB SanDisk Cruzer Ultra fit thumb drives in RAID0 as download volume. I want to use 2x 32GB instead of 1x 64GB to enhance the write speed (because it will double the write capacity with 2 USB drives and hopefully 2 USB 2.0 ports will increase the USB 2.0 bandwidth bottleneck a little).

I expect that the server will download around 25GB a week to the USB drives (and repair and then extract the data to the RAIDZ hard drives).

I have a few questions about this setup:

1. Is this still useful in a FreeNAS setup with RAIDZ? I'm mainly interested in prolonging hard drive lifetime.
2. Flash memory will wear out. Conservative numbers show that flash memory can handle about 10.000 write cycles. If that's true then 64GB storage * 10.000 cycles / 25GB weekly data writes / 52 weeks per year = 461 years before my USB drives will wear out?
3. Any other thoughts on this setup (in general)?

Thanks!

 

[Bidule0hm]

This:

this allows the drives to idle and spin down more often.

Is in direct conflict with this:

I'm mainly interested in prolonging hard drive lifetime.

The drives last longer when they are continuously running.

Besides, USB sticks are highly unreliable, we've learned that with them used as boot drives for FreeNAS.

TL;DR: it's a very bad idea.

 

[m0nkey_]

The only time I would recommend using USB drives at all is for booting FreeNAS and nothing more. It's likely your USB ports are on the same bus, which will limit the write speed, regardless if you stripe or not. You're not going to see any kind of performance gain by doing this. I'd advise against it, your heading for a world of hurt.

 

[jant90]

Great, thanks for the quick replies guys! I will create a temp download folder on de RAIDZ pool then and forget about the USB drives altogether. I hope te RAIDZ pool will be able to keep up with several clients streaming content and downloading/repairing/extracting via SABnzbd at the same time.

Btw my reasoning was: less power-on hours equals longer life for HDD's but I guess I was wrong. Sometimes drives are completely unused for several hours and that would probably save some power during the night though.

Will FreeNAS make sure that drives are continuously running and won't spin down (only idle)? Or do I need to configure this myself?

 

[Bidule0hm]

Btw my reasoning was: less power-on hours equals longer life for HDD's but I guess I was wrong. Sometimes drives are completely unused for several hours and that would probably save some power during the night though.

Yes but no. You'll save some wear on the drive because of less POH but the drives are incredibly precise and fragile mechanical systems and they don't like when parameters change abruptly (temperature, spinning up/down, ...). There's a limit where the good exceed the bad but it's not very well defined, we usually use one spin up/down per day as a limit.

Will FreeNAS make sure that drives are continuously running and won't spin down (only idle)? Or do I need to configure this myself?

If you've setted the HDD standby to always on and the APM to disabled (both in Storage --> View Disks) then you can be sure they won't spin down ;)