Another thing to consider when choosing to have Raid over Mirror/ix is the
level at which the protection is handled. Raid is handeled at the hardware
end and Mirror/ix is handled at the O/S end. If you have an application that
is write intensive Mirror/ix is actually detrimental to your system
performance because the O/S has to actually do two writes for every one
write request. I've heard that for read intensive processes the performance
is a wash or Mirror/ix is better. Also with Mirror/ix on 6.5 there is a
problem with mirrored volumes being dropped if there is a large number of
disks and large number of I/Os. We have put a fix request to HP and it has
made it to their lab but has a low priority. Hp has indicated the low
priority is due to plans to drop the Mirror/ix product.

Rich Holloway
Providence Health Plans
Phone (503) 574-7457

The opinions expressed here are strictly mine and do not represent
anybody else, company, or organization.

"In complete darkness we are all the same. It is only our knowledge and
wisdom that separates us. Don't let you eyes deceive you." Janet
Jackson, Rhythm Nation album.


-----Original Message-----
From: Emerson, Tom # El Monte [mailto:[log in to unmask]]
Sent: Thursday, November 30, 2000 9:17 AM
To: [log in to unmask]
Subject: Re: [HP3000-L] Mirrored Disk vs. Raid


Maybe that's the "key" -- regular PREVENTATIVE maintenance -- we recently
had a "problem" that PM'ing would have prevented [well, at least I THINK it
would have prevented the problem] -- the fan in the power supply of the disk
cabinet had gotten so gunked up with dust that it simply stopped working.
Once it stopped, the power supply "overtemped" and shut off -- as you can
imagine, a "bad thing" for a power supply to do -- and brought production to
a halt...  Other than the fact it it physically inaccessible, a quarterly
vacuuming out of accumulated dust would have prevented the problem [or, at
the very least, would have shown an indication a problem was developing well
enough in advance the fan or supply could have been replaced with minimal
interruption -- on the good side of things, however, since this was an
external drive box, and even though these are "system volume set" disks, we
were able to leave the system "running" when we replaced the supply, once
the drives spun back up, everything picked up where it left off...]

> -----Original Message-----
> From: Bartram, Chris [mailto:[log in to unmask]]
>
> If you recall, the MTBF on the old 7933/7935 disc drives was about 13
> months. When I ran a shop of series 70s, we had CEs in to do
> PMs at least
> once a month - most of the work they did was working on the
> disc drives
> (changing filters, checking the mechs, etc.)
>
> When you compare the amount of data and the MTBF on those old
> drives (13
> months/404MBs) to the newer 18+Gb drives, we can't complain
> too much (not
> that that stops me... I still lose way to many of the 4.3Gb
> discs in our
> production box. ;-) ).
>
>  -Chris Bartram