Block size recommendations for RAID 5 (Promise SX6000)

[vetteguy]

I just got all the hardware in for my new server (see it in my sig) and am getting ready to set up my RAID array. I am (as the title says) using a Promise SX6000 6-channel IDE RAID card. I have 6 of the WD 80GB special editions attached to it, and will be setting it up as RAID 5. My question is, what would be the best block size? I was looking over the "IDE RAID Comparison" on the main site here, and although my specific card wasn't reviewed, the hardware RAID 5 cards that were used a 128k block size. Would that be my best bet? Or does someone have a better recommendation? My experience with RAID has always been just as a user in servers at work, I've never actually designed my own array, so any advice is appreciated!

 

[SCSIRAID]

The correct stripe unit size depends on what kind of workload you are throwing at it. If you are doing mainly unitasking and are reading large files (video, streaming media etc) then you want the stripe units to be large so each IO gets all the drives transferring in parallel thus maximizing you MB/sec. If you are multitasking and doing small file work (like web serving, database etc) then you want the stripe unit size small (8-16K) (basically the same size as the typical request) so that each IO hits only a single drive and leaves the other drives to serve other requests. This maximized the number of IO's per second the array can handle. There is no single 'best' answer for all cases. It all depends on what you are doing.

 

[vetteguy]

Well, this is for my generic file/print server at home, so really the load will vary greatly, from mp3s to video files to Word/Excel, etc. On average I would say that there would be more "big" files, though, so maybe a 64 or 128? Since this is just for me I'm not too concerned about benchmarking throughput and making it perform like a enterprise-class server, and really the RAID is just for redundancy.