My server will be handling numerous simultaneous flash 5% (3mb or less) video/music streams and 95% (less than 500kb) image views

Which is better in terms of real-world performance (speed and dependability, not capacity)?

1. 3x Hitachi 7k500 SATA (http://www.storagereview.com/HDS725050KLA360.sr) in RAID0
using the onboard RAID controller of IP35 Pro

2. 4x Hitachi 7k500 SATA (http://www.storagereview.com/HDS725050KLA360.sr) in RAID5
using the onboard RAID controller of IP35 Pro

3. 1x Hitachi 15k300 SCSI (http://www.hitachigst.com/portal/site/en/menuitem.f7da5b80da420cb0483bad24eac4f0a0/)
with LSI21320-IS (in a 32bit PCI slot)


Does RAID improve seek time? If not, considering the files my server will be handling, will the seek times of the SATA RAID configurations be the bottleneck? What kind of transfer rates will the SATA Hitachi's in RAID achieve? How much do these transfer rates play in the overall time?


Thank you for the help!

You need a storage subsystem that handles the maximum number of IOPs.

Never use RAID 0 on a server.

Onboard RAID controllers tend to be consumer-oriented. They don't perform too well under server conditions. I would only investigate this solution if you have a need for the high capacity that the SATA drives can deliver.

Best solution mentioned. 32-bit PCI will limit sustained transfer rate somewhat, but that's irrelevant with your total throughput needs. You need the high IOPs that the SCSI drive can deliver.

No. In fact, it increases the total access-to-data times.

No, the seek times are not really the issue, it's the sustained IOPs that the onboard RAID controller can deliver. Sustained transfer rates may be higher, but that doesn't help you in this situation.

Great

I intend to buy another 15k rpm SCSI and put the two in RAID1. Considering just the one hard drive averages about 100 mb/s average transfer rates, can I expect to achieve an min/average/max of 133 mb/s read rates (bottlenecked by 32bit RAID controller)? How about write speeds? Will the diminish significantly?

What is IOP?

Thanks for the informative reply

RAID 1 (mirroring) typically is done specifically for the redundancy, not for speed increases. Some higher end RAID controllers (LSI, 3Ware) can get somewhat increased read speeds in RAID 1 by intelligently spreading read commands to both drives. Write speeds will always be equal to that of a single drive.

IOPs = I/O operations per second. It's a measure of how many random read/write requests the hard drive can sustain per second. It's the most important benchmark for drives that are being used in a server environment where several applications are accessing the drive at the same time.

Go to Storagereview's Performance Database, pick the "IOMeter File Server - 8 I/O" benchmark and hit sort. The graphs show the IOPs that each drive can deliver.

You can see that a 15K.5 SCSI Seagate Cheetah can do 275 IOPs, while the best 7200RPM SATA drive (Seagate Barracuda ES.2 1TB) can only do 128.

You have to keep in mind that the total throughput on your system is not the goal, but the ability to answer all requests in a timely fashion.

well i just found out my card (LSI 21320-IS) only supports RAID0 :\ ... I should have guessed IS stood for integrated striping before jumping the gun and purchasing

So I'll put two 15k300 Hitachi's in RAID0 and hope for the best

What stripe/clustersizes should I use given that my server will be handling 95% (100-400kb) images, 5% (1-3 mb) videos/music?

Thanks for the help

I strongly recommend against RAID 0. You might want to see if the vendor you purchased the card from will exchange it for a card that can handle RAID 1.

If you really want to use RAID 0, almost all modern RAID cards operate optimally with a 64K stripe size. The NTFS file system performs optimally with a 4K cluster size.