phil walker wrote:
Hi All,
I have just read a slide from the U2 University sessions whereby it
states...
RAID 0+1 is absolutely the fastest implementation possible for disk
drives
t>Internal and External Disk Drives -Raid 0+1, striping and
mirroring tWhen a mirrored disk drive is not committed to a WRITE,
it is available for a READ tAdditional throughput from RAID 0+1 is
about 40% tParity WRITEs never are in contention with the
production disk drives. RAID 5 will have a parity WRITE be in
conflict with the Production Disk Drives tHW level RAID
implementation is far better than SW striping and HW mirroring
tStripe size was 128K. Any larger, and a file can be on a
singledisk drive.
Can anyone tell me how it compares performance wise through theory or
experience to RAID 10 which as a configuration is more fault tolerant
and easier to rebuild?
Raid O/1 and Raid 1/0 are exactly identical in terms of performance for
an operational array. If you look at the actual IO operations, there is
no difference from 0/1 and 1/0. Many hardware Raid vendors are sloppy
and it is hard to tell if they are 1/0 or 0/1. Fortunately, it does not
matter. I tend to call either RAID-10.
The global statement "RAID 0+1 is absolutely ..." is also incorrect.
The statement is usually true for applications that are doing a mix of
random reads and writes to the array. If however, you have an
application that is doing single-threaded large linear writes, then
raid-5 or raid-50 will actually out-performance raid-10. For the users
of this particular list, this probably does not matter, but there are
cases where linear write throughput is important (think data logging).
One thing to remember with RAID-10 is that read performance improves as
you add drives, but only for applications that multi-thread. If you
have a single process that is doing random reads, adding drives will
only help with multiple users. The single user case will still be
limited by the random read speed of a single drive. This is why we are
working with Flash drives where the single thread read speed can be 40X
that of a 15K RPM HDD, but that is another thread.
Doug Dumitru
EasyCo LLC
Cheers,
Phil. ------- u2-users mailing list [email protected] To
unsubscribe please visit http://listserver.u2ug.org/
-------
u2-users mailing list
[email protected]
To unsubscribe please visit http://listserver.u2ug.org/
