RE: Reducing downtime for backups

["jt" <jt@xxxxxx>]

Chris, Phil

I think it's pretty easy to say which is the best alternative here...

However, being accurate is another thing, entirely...;-)

It's real hard for me to guestimate performance...  I think others on this
list are better to speak on this issue.  But since you asked, I tend to
think more arms would help reduce the backup downtime a lot, but I'm
guessing they're fairly expensive, relative to a new tape drive, which would
also help a lot.  (Haven't priced these, though.)

It comes down to what you said, Chris:  where do you want to spend your
money, disk or tape (or programming).  The costs of the different
alternatives (which can be determined) needs to be compared with the
expected performance gains (which is a tough call, IMHO)...

jt


| -----Original Message-----
| From: midrange-l-admin@midrange.com
| [mailto:midrange-l-admin@midrange.com]On Behalf Of Chris Bipes
| Sent: Friday, November 30, 2001 7:38 PM
| To: 'midrange-l@midrange.com'
| Subject: RE: Reducing downtime for backups
|
|
| But as you increase disk arms, i.e. drives, you get higher
| through put.  As
| your through put goes up, your IOP, CPU and Main ASP Disk load will go up.
| Now if those do NOT become a bottle neck, you will still see 90+% disk
| utilization on your secondary ASP BUT your run time will go down.
|
| Any body want to back me up on this?
|
| And I do not take any offense to you or anyone on this list
| questioning what
| I post.
|
| Christopher K. Bipes    mailto:ChrisB@Cross-Check.com
| Operations & Network Mgr  mailto:Chris_Bipes@Yahoo.com
| CrossCheck, Inc.                http://www.cross-check.com
| 6119 State Farm Drive   Phone: 707 586-0551 x 1102
| Rohnert Park CA  94928          Fax: 707 586-1884
|
| -----Original Message-----
| From: prumschlag@phdinc.com [mailto:prumschlag@phdinc.com]
| Sent: Friday, November 30, 2001 1:22 PM
| To: midrange-l@midrange.com
| Subject: RE: Reducing downtime for backups
|
|
|
|
| Chris,
|
| Don't take this wrong, but I have trouble swallowing that.  I have to go
| back to
| basics on this and in my (admittedly simplistic) view it goes like this:
| CPU -
| Fast;   Disk - Not So Fast,   Tape - Really Slow.  For this job,
| the CPU has
| nothing else to do, so it will always be waiting on the disks, so
| no matter
| how
| many I throw at it the disk busy percentage will always be high.  If my
| lousy
| memory serves me correctly, IBM invented *SAVF files for the
| express purpose
| of
| reducing downtime for backups.  Has tape processing improved so much that
| one
| tape drive can record data faster than 6 read/write heads on
| disk?  Or is it
| possible that the RAID processing on these disks is causing so much
| thrashing
| that the whole system is bouncing up and down in the computer room?
|
| Phil