Is RAID 5 a mistake?

[enderzero]

My plan for the new system I'm building has been to run a 128GB SSD as my system drive and use 3 SATA drives in RAID5 off the board as a data drive.

As I've been reading about it more it sounds like this might be a mistake. I understand redundancy and I'm not looking for anyone to tell me that this doesn't solve backup issues, etc. But will the 3 SATA drives in RAID5 actually give me lower performance than a single SATA drive?

What order would the following setups take for average transfer fastest to slowest. I always assumed 2, 5, 4, 1, 3 - but is that incorrect?

1. Single SATA Hard Drive
2. 2 SATA HDDs Striped RAID 0
3. 2 SATA HDDs Mirrored RAID 1
4. 3 SATA HDDs RAID 5
5. 4 SATA HDDs RAID 5

Thanks!

 

[sminlal]

RAID-5 will perform more poorly for writes, but it has the potential to perform better for reads. Assuming your list goes from slowest to fastest transfer rates, I'd say that it's basically in the correct order (single drive = slowest, 4 drives in RAID-5 fastest), except that I'd rate RAID 0 as faster than RAID 1. And again, any RAID-5 configuration will be the slowest when it comes to writes.

You should also understand that RAID improves transfer rates only - not access times. So you can expect it to help with reading or writing large files, but not to help that much when it comes to accessing lots of small files or for other random access workloads.

 

[enderzero]

Thanks for the reply.

Just to be sure I understand, it will take longer to transfer a file from the SSD to a RAID5 array then it would to transfer the same file to a single hard drive? But it will take less time to transfer a file from a RAID5 array to the SSD?

Any idea what kind of time we are talking about (or transfer rate) for instance with a 1GB file and with 200 5MB files. Any benchmarks out there on this?

Can you tell

 

[tokencode]

RAID 5 will be faster for reads than a single drive and slower for writes, in your example, yes transferring from RAID 5 to SSD would be faster and from SSD to RAID 5 would be slower.

 

[enderzero]

Thanks! Any idea what kind of numbers I'd be looking at?

Right now my HD Tune Transfer average on one of these drive (2TB Seagate Green) is 109 MB/sec.

Thanks

 

[sminlal]

If you're using motherboard RAID then my guess would be that the transfer rate for writing to the RAID-5 set would be somewhere around half that of writing to a single, non-RAID disk.

 

[Pherule]

Tip: just use raid 0 and keep good backups.

 

[FireWire2]

Motherboard RAID should be use as a secondary storage, it's never intend as high performance raid.