Let's talk about solid state - ZFS cache

[rs232]

Well, the title says it all really.
I wanted to try to add a SSD to my zpool to see how performance would change.

Does anybody have experience on this? What is the minimum access time you would recommend?

I read somewhere that the size of the cache should be 30ish time the amount of RAM?

http://www.ebay.co.uk/itm/Solid-State-D ... 4165401a6e


Appreciated!
rs232

[raulfg3]

I can only speak about my experience, this mean that yours or others can be different.

I use a 90GB SSD and I do not notice any improvements on a week that I use it.
My scenario is a Home NAS , and only do esporadic transfer of medium / big files ( eg: video files, series, and photos), 5 or 6 times a week.
all files are diferent ones from others so really dificult for a cache device to find similar patterns.

So my recomendation for a HOME NAS is do not waste money/Disk, use to buy more RAM, but perhaps for SOHO or enterprise enviroments performance was slightly different.

PD: In all forums recomends to use 2 SSD in mirror to avoid data lost ( if use only one SSD and this SSD have problem, you lose your data too, not only your cache device).

[ChriZathens]

Although I personally have no experience with ZFS generally, from what I read here and there, it is better to spend your money for more RAM and not for SSD cache disks..

[ku-gew]

I put a USB stick on my desktop installation of ZEVO ZFS and I also cannot see substantial changes in performances (a USB stick is still faster than an HDD for reads below 4 MB).
I think it makes sense only for databases, as written in the guide, where you have small reads and a lot of static data.