09-24-2014
Hi,
Unfortunately having only a single drive here is going to skew these figures, to test this properly you'll need multiple physical drives.
There are multiple impacts here - mostly from the hard drive, the seek time and latency will be major contributors as virtual box only creates a contiguous file if you specify that it should preallocate all the disk space. Other than that it will scatter the writes all over the disk if you specify that it should grow the file as required.
I don't think that this is really a suitable way to evaluate the performance of any RAID as it's all on one physical disk.
Regards
Dave
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HP(4) Kernel Interfaces Manual HP(4)
NAME
hp - RH-11/RP04, RP05, RP06 moving-head disk
DESCRIPTION
The octal representation of the minor device number is encoded idp, where i is an interleave flag, d is a physical drive number, and p is a
pseudodrive (subsection) within a physical unit. If i is 0, the origins and sizes of the pseudodisks on each drive, counted in cylinders
of 418 512-byte blocks, are:
disk start length
0 0 23
1 23 21
2 0 0
3 0 0
4 44 386
5 430 385
6 44 367
7 44 771
If i is 1, the minor device consists of the specified pseudodisk on drives numbered 0 through the designated drive number. Successively
numbered blocks are distributed across the drives in rotation.
Systems distributed for these devices use disk 0 for the root, disk 1 for swapping, and disk 4 (RP04/5) or disk 7 (RP06) for a mounted user
file system.
The block files access the disk via the system's normal buffering mechanism and may be read and written without regard to physical disk
records.
A `raw' interface provides for direct transmission between the disk and the user's read or write buffer. A single read or write call
results in exactly one I/O operation and therefore raw I/O is considerably more efficient when many words are transmitted. The names of
the raw files conventionally begin with an extra `r.' In raw I/O the buffer must begin on a word boundary, and raw I/O to an interleaved
device is likely to have disappointing results.
FILES
/dev/rp?, /dev/rrp?
SEE ALSO
rp(4)
BUGS
In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, and write scribbles on the tail of incomplete blocks.
Thus, in programs that are likely to access raw devices, read, write and lseek(2) should always deal in 512-byte multiples.
Raw device drivers don't work on interleaved devices.
HP(4)