RAID issues with dissimilar speed drives?

[Peter Blanchard]

OK. I have a NAS that uses 10 1TB 10k RPM Velociraptor HDDs. It's SATA only. Squeezed into mATX case, with a FlexATX mobo.

HDDs are ancient and bound to fail at some point.

Whilst there are there are refurbished(?) and even a handful of new drives on the market, they are expensive. When drives fail, I'll replace them with something cheaper.

Probably 1TB SATA SSDs.

My understanding is an array is limited by the speed of the slowest drive? Or is it worse than that?

I have the option use the drives in a different and higher performing machine I can use SAS controller in. 1TB 10k SAS drives are much cheaper.

Does mixing SATA and SAS drives in an array cause any problems?

 

[alaricljs]

NAS model (or DIY)?
OS?
Hardware / Software RAID?
What level?
Controller? (multiple)?

If there's going to be an issue it's specific to some particular item or combo. In general, no big deal.

 

[Chriggel]

Some HW RAID controllers don't even support mixed arrays. In a SW RAID, you could force it, but it's usually not the best idea. From a performance standpoint, mixing drives with different speeds either drags down the entire array or gives inconsistent performance.

Honestly, 10x1TB Velociraptor sounds bad. 10x 1TB 10k SAS drives sounds equally bad. 10x1 TB SATA SSDs sounds somewhat better. Do you need so many drives for your workload, are you limited by IOPS or bandwidth? If not, then this is super inefficient and you could maybe think about 2x10 TB 3.5" 7.2k as a mirror instead.