topic RAID speed in Operating System - Linux

RAID speed

Piotr Kirklewski — Thu, 14 Oct 2010 01:38:45 GMT

Hi there
How do I calculate the raid 5 speed in Mbps or Gbps?
Let's say I have 5 x 7200RPM HD.
Best regards
Peter

Re: RAID speed

Steven Schweda — Thu, 14 Oct 2010 02:42:36 GMT

> Let's say I have 5 x 7200RPM HD.

Let's say that we also know the average seek
time of these disks, and the interface type
of these disks (IDE/ATA, SATA, SCSI, SAS, FC,
or whatever), and its speed, and the speed of
the adapter to which they're attached, and
the speed of the (PCI?) bus to which that's
attached, and the speed of the CPU to which
that's attached, and all kinds of other data
which we don't know. You'd probably still
never get anything better than a rough
estimate.

If you really want to know how fast some
collection of hardware will be at some
particular task, then you should probably
run some real test, ideally using some real
data, in some realistic conditions.

Re: RAID speed

TwoProc — Thu, 14 Oct 2010 13:19:42 GMT

Hey Piotr,

I recommend a program called Bonnie. It does a pretty decent job of doing I/O throughput tests on disks. If you want check for more concurrency, launch several at a time.

Source code is here:

http://www.coker.com.au/bonnie++/

Re: RAID speed

Alzhy — Mon, 18 Oct 2010 12:28:52 GMT

Use bonnoe++ and iozone. If you want to get fancy and want to predict how your Oracle Load will perform -- use ORION (Oracle Input Output Numbers) tool.

Google them all for locations and instructions.

If you wanna get fanacy and would like to run Oracle DB -- then you can try using SwingBench.

Bottom line: It all depends on how your SATA controller is built on your PC or server board (a concept called "roping"). If your indivdidual SATA ports to which each SATA drive atatches is on its own "rope" or bus -- then expect full performance of each SATA drive (~ 120MB/sec sustained reads). So for a 5 Disk RAID5 Setup with 3+1Parity + 1 hot spare - you can get roughly 250 to 300 MB/sec read and about half of that for writes sustained. And this is with your typical consumer mATX or ATX PC motherboard sporting 5 to 6 SATA-II ports.

(This is based on experience running a 3+1P 1TB 7200 rpm 32MB Cache RAID5 set up on an ASUS M4A75-M mATX AMD motherboard running CENTOS 5.5 (mdadm - software RAID) and bonnie++ and iozone and ORION benchmarks.