NON-SSD Cache Drive? (15K SAS)

[guldan]

Hey Guys,

I have a pretty sweet setup coming together here, Dell 2950 w/ 2x 72GB 15k 4x 300GB SAS drives attached to a MD1000 w/ 15 720GB HDDs (via SAS HBA). My plan is to sell the 750GB HDDs and replace them with 1TB or 2TB drives as grow my pool as needed.

Seeing as I have so many spare drives (including on my 2950 OS box) I want to utilize the cache drive, would it be wise to use the 2x 73GB or maybe 2x 300GB 15k's for ZFS Cache? do you have to use an SSD?

 

[paleoN]

I have a pretty sweet setup coming together here, Dell 2950 w/ 2x 72GB 15k 4x 300GB SAS drives attached to a MD1000 w/ 15 720GB HDDs (via SAS HBA).

What's your pool configuration?

Seeing as I have so many spare drives (including on my 2950 OS box) I want to utilize the cache drive, would it be wise to use the 2x 73GB or maybe 2x 300GB 15k's for ZFS Cache?

No, it wouldn't be wise. Whatever you use for a SLOG or L2ARC device you want it to be an order of magnitude faster at writes & reads (latency) respectively. 15k drives are not. Which currently means a SSD or some other form of NVRAM.

 

[guldan]

What's your pool configuration?

Nothing currently as I plan to sell them, I just booted up Freenas to see if the drives would show up through the HBA and was pleasantly surprised when they did.

I'm really not sure how I want utilize the MD1000

I might make a 6 x 2TB RaidZ2 for my main storage array then create a 2nd backup array (open to ideas) and then do a daily sync of files between the two. The only problem with that is they would be in the same physical device and if that fails then I lose everything.

 

[paleoN]

I might make a 6 x 2TB RaidZ2 for my main storage array then create a 2nd backup array (open to ideas) and then do a daily sync of files between the two. The only problem with that is they would be in the same physical device and if that fails then I lose everything.

You're right, it's not a true backup, but a second pool will protect you from other failures, e.g. pool metadata corruption. It also allows you to mess around other things you might not want to do on your main pool.