speed comparison between striped & spanned volumes

[ikon]

I've been looking into using the WHS2011 Disk Manager to set up my data volume(s) in WHS2011. Microsoft tells us that striped volumes are faster, but they don't say how much faster.As part of my investigation I just ran some simple ATTO Disk Benchmark speed comparisons between 2 and 3 drive striped volumes and spanned ones. Here are the results:

 

 

 

So a 2 drive stripe is almost exactly twice as fast as a 2 drive span. And adding drives to a stripe increases performance while it does nothing for spans.

 

The pros for stripes: 2x or more faster and speed increases with more drives; the cons: impossible to add or remove drives/shrink or extend volumes.

 

The pros for spans: easy to add or remove drives/shrink or extend volumes; the cons: only half as fast (or even slower) and speed is static..

 

I haven't yet looked into concatenating volumes; that may help overcome the cons.

 

But, I would be remiss if I didn't look to see if there are RAID or other cards that can give me the advantages of both, without the cons. Anyone got any ideas?

[timekills]

There is another downside to striping/upside to spanning. Losing one drive in a span means you lose just the data on that drive, not the data across all the striped drives. Lose one drive in a striped (i.e. RAID0) set and you lose the whole array. Certainly striping will be faster as you are effectively reading to and writing from multiple physical hard drives at one time rather than just one at a time with spanning.

 

Basically any current RAID card - including the 3ware one you mentioned (it supports "Online Capacity Expansion and RAID Level Migration") - can allow for an addition/expansion to a RAID0 striped array. Most allow you to do it while the array is in use, it just can take a while for the extra drive(s) you add to become available. For a RAID0 set it's usually quite quick; a RAID5 can take hours/days depending on the array size.

 

Your card even supports online migration of arrays.

Edited June 5, 2011 by timekills

[ikon]

There is another downside to striping/upside to spanning. Losing one drive in a span means you lose just the data on that drive, not the data across all the striped drives. Lose one drive in a striped (i.e. RAID0) set and you lose the whole array. Certainly striping will be faster as you are effectively reading to and writing from multiple physical hard drives at one time rather than just one at a time with spanning.

 

Basically any current RAID card - including likely the 3ware one you mentioned - can allow for an addition/expansion to a RAID0 striped array. Most allow you to do it while the array is in use, it just can take a while for the extra drive(s) you add to become available. For a RAID0 set it's usually quite quick; a RAID5 can take hours/days depending on the array size.

Thanks for the reply. I didn't state the part about losing a spanned drive cause I was thinking it was inherent in the definition of a span. I'm glad you made it clear as I obviously didn't.

 

I really am hoping the card can allow adding and removing drives from a RAID0; that would be very cool.

[pcdoc]

Nice testing summary. What kind of drives were you using? For comparison here is what I am getting from an 8T (5x2t) RAID 5. There is definitely a difference between striping and mirroring when it comes to performance. RAID 5 gives you closer to the striping performance plus redundant.

 

 

[ImTheTypeOfGuy]

Interesting data. I have a software striped array (4x2TB) and I get reads around 400 and writes around 350. These are averages.

 

I am curious why you tested striping versus spanning. Spanning is the same as one disk as it writes the data to disk 1 until it is full and then it writes to disk 2.

[ikon]

Nice testing summary. What kind of drives were you using? For comparison here is what I am getting from an 8T (5x2t) RAID 5. There is definitely a difference between striping and mirroring when it comes to performance. RAID 5 gives you closer to the striping performance plus redundant.

 

 

They're just some old 250GB Maxtor enterprise drives I had laying around. I have two WD RE4-GP 2TB drives being SpinRited for the new server and I plan to add 2 more of them for a total of 8TB.

[pcdoc]

They're just some old 250GB Maxtor enterprise drives I had laying around. I have two WD RE4-GP 2TB drives being SpinRited for the new server and I plan to add 2 more of them for a total of 8TB.

 

 

Thanks. This array has 5 2T EADS drives which I found to be a bit faster than the EARS drives as I have a couple of each.

[ikon]

Thanks. This array has 5 2T EADS drives which I found to be a bit faster than the EARS drives as I have a couple of each.

Thanks very much for the feedback pcdoc. For this test I didn't worry about what drives I was using as I was going for the stripe vs span comparison and I figured the important thing was to keep the testing parameters the same. I am sure many newer model drives would outperform the ones I used, if for no other reason than they have higher areal densities today.