New build. Sata2 onboard or "crap" Sata3 on PCIe?

[skywise_ca]

Building a new home NAS out of some slightly old AMD hardware. (2x6378 Opteron CPUs, 256G RAM, super micro H8DGU-F MB)
The MB uses an AMD SP5100 chip for SATA (2.5, 300MB/sec)
I also have a generic SATA controller on PCIe (Marvell 88SE9235 AHCI SATA) which has 4x 600MB/sec ports.

Now, the hardware guide for FreeNAS says all PCIe SATA cards are crap. But are they worse than the 1/2 speed onboard SATA?
I'll be using 3x8TB drives for now. (replacing 6x 4TB drives in the current NAS)

 

[Stux]

8TB drives will probably peak below 300MB/s anyway.

Not sure how bad the AMDSP51000 SATA ports are.

Or you could get a decent HBA (LSI) which supports 8 drives and be done.

Re the SATA card... you could always try it.

 

[Johnnie Black]

No hard drive currently on the market can do more than 250MB/s, SATA2 is enough, SSDs are a different story.

 

[danb35]

Now, the hardware guide for FreeNAS says all PCIe SATA cards are crap. But are they worse than the 1/2 speed onboard SATA?

Probably so--and as already stated, the extra speed is irrelevant anyway for spinning rust.

 

[skywise_ca]

I did some testing with dd and one of the 8T drives, SATA 3 card would get 240MB/sec.
Same drive on the onboard SATA 2, 220MB/sec.
I'm calling it close enough, I've got enough RAM in the box to cache forever.

Thanks for the wisdom!

 

[tvsjr]

3x8TB drives is suboptimal... at that drive size you really need to run RAIDZ2, meaning you're only looking at the capacity of a single drive.

 

[skywise_ca]

3x8TB drives is suboptimal... at that drive size you really need to run RAIDZ2, meaning you're only looking at the capacity of a single drive.

True but I was looking at price and into the future, I'd like to keep this system for quite a few years and 4T drives are already quite dated.

The plan is to have the old NAS stick around as near-line backup, a couple of big external drives in the safe as second backup and a colo set of drives for important stuff.

 

[Stux]

There's a tradeoff between number of spindles and size of drives.

6 4TB drives in RaidZ2 gets you the same capacity as 4 8TB drives in RaidZ2, but you only have to purchase 24TB vs 32TB... which is cheaper. And its faster.

So does it make more sense to go for more but smaller drives now? And in the future add another 6 drives?

Basically, you *could* go with RaidZ1 and 3 8TB drives instead of 6 4TB drives in RaidZ2... but the RaidZ2 would be orders of magnitude more reliable. And the drive cost is about the same.

I understand not really wanting to purchase 4TB drives... but 8TB drives and RaidZ1 is a bad idea. Assuming you actually want to avoid pool failure.

Either way, you need a backup, so worst case, the RaidZ1 fails, at least you can restore.

...

Little example... I just had a 'hard drive failure' in a 5way RaidZ2. It was actually a bay failure, where a cable had gone faulty... as part of trying to trouble shoot that, I ended up corrupting some of a second drive (117,000 errors...). Oh dear. Luckily I had RaidZ2 and it was no biggy. Once I found and fixed the faulty cable the array rebuilt successfully. If it had been RaidZ1, I'd be restoring over ethernet... which would probably take a couple of weeks.