Stripe size rules of thumb?

[Savage1701]

Are there any general rules for configuring stripe size on drives/RAID arrays? I've seen some people wanting to use smaller stripe sizes (as low as 512 bytes) on SSD drives. I've seen some posts saying 64K, the usual default, is best.

What are the advantages/disadvantages to larger/smaller stripe sizes? What types of files are best for what stripe size? What stripe sizes line up best with what uses?

Thanks for any thoughts on the matter.

 

[CCT]

Covered here;

https://www.techspot.com/vb/topic1596.html

 

[adweston]

The rule of thumb is don't use "RAID" 0 unless your data is worthless... Stripe size won't matter when it craps out and you lose everything on both drives.

... And it's not "RAID" by definition, because RAID is "Redundant Array...." and "RAID 0" is anything but redundant.

Oh.. and despite cutting your meantime between failure (MTBF) in half, no matter what stripe size you choose you won't notice any significant increase in performance.. Ignore what HD Tach says, because it's a "pseudo" benchmark.. In other words, it's a simulated benchmark that doesn't in any way, shape or form correspond with real world results.

One Velociraptor, while being infinitely more reliable, will give you similar, if not better, real world performance.

If you're INSISTENT on using it, smaller stripe sizes equate to less wasted space, ideal for a myriad of really small files. The problem is, of course, that if all you're doing is loading really small files, "RAID" 0 will give you absolutely no real world performance gain.

Thus, the 64k would be accurate...Because you'd want to be storing massive files on it or not wasting your time at all.

 

[Savage1701]

First off, CCT, thanks.

Adweston - I agree with you. I was not really thinking RAID 0 at all, and I agree with you about MTBF and synthetic benchmarks vs. the real world.

My more specific questions were: 1. Is it better to go with a smaller stripe size on an SSD boot volume? 2. What might be the optimal stripe size for a 6+TB RAID6 array used almost exclusively to store 1GB and larger DV files.

Thanks.

 

[adweston]

For large files like that, you want a 64kb stripe size.

On an SSD boot volume, you'd want to go smaller, possibly half that.

 

[Savage1701]

Thanks. That's what the default is on the RAID6 so I will leave well enough alone.

 

[CCT]

Just out of general interest, I found these 2 links. One deals with SSD Raid stripe setup fairly well and the other with Matrix Raid which gives the best of both Raid 0 and 1.

http://www.tomshardware.com/forum/246485-32-slow-performance-ssds-adaptec-raid-controller

http://techreport.com/articles.x/8059/1

 

[adweston]

As soon as I see "HD Tach" as a basis for their argument... I close the page.. HD Tach is a joke (but then again, so is RAID 0)