Re: USEOPTBLK effect on which drives? -- MIDRANGE-L

Title: RE: USEOPTBLK effect on which drives?

Dan, from what I can find, the 7208 can only be attached via the 2729 (PCI) or 6534 (SPD) cards, neither of which supports hardware data compression. The documentation on this is sketchy (to put it mildly!), but I think that if you rely on the device to do the compression, you'll end up with the best results. Swapping to the -222 model may be you're only hope of getting the backup to stay at 2 tapes, unless you can figure out a way to not back something up....probably not what you want to do.

PS. Every time I ask about software compression, I'm told it's inefficient and doesn't get the data as dense as it could be.

Sue

----- Original Message -----

From: Bale, Dan

To: midrange-l@midrange.com

Sent: Tuesday, August 14, 2001 12:28 PM

Subject: RE: USEOPTBLK effect on which drives?

Hi Sue! Is H.A. your middle name? <g> Is the fishin' good in Silverlake?

Speed is not as much a factor as is the desire/goal/requirement to get the backup done on two tapes and not three. I risk alienating the users who now have to put in a second tape first thing in the morning if I tell them that there's now a third tape to deal with every day.

Unless we reach a crisis point with our ability to do a complete backup, there will be no further hardware expenditures. The best I may be able to do is to switch a 7208-222 from one of our other boxes with the 7208-012 on the capacity-challenged machine so that I can use 7GB cartridges as opposed to the 5GB's.

COMPACT(*YES) brings a syntax error at V3R7. The only valid values are *DEV and *NO. I use the default value of *DEV. According to the V4R5 system handbook, it appears that the 7208-012 supports both the HDC (Hardware Data Compression) and the IDRC (Improved Data Recording Capability) compaction algorithm. But HDC seems reliant on the IOP; do all of the IOP attachments for the 7208-012 support HDC? (FWIW, it appears that we are using IOP #2621.) Also the compaction algorithm appears to be dependent on the tape subsystem controller; is this "built-in" to the tape drive hardware?

*IF* our 7208-012 supports both HDC & IDRC, am I getting the maximum capacity by specifying DTACPR(*YES) & COMPACT(*DEV) ?

Dan Bale
IT - AS/400
Handleman Company
248-362-4400 Ext. 4952
D.Bale@Handleman.com
Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)

-------------------------- Original Message --------------------------

-----Original Message-----
From:   S Baker [SMTP:gonfishinmn426@yahoo.com]
Sent:   Tuesday, August 14, 2001 7:50 AM
To:     midrange-l@midrange.com
Subject:        Re: USEOPTBLK effect on which drives?

Dan, USEOPTBLK works on the 7208-342 but not the other 7208 models.

DTACPR is really slow ... that's software compression of the data before sending to tape.
Better to use COMPACT(*YES) and have the tape hardware do the compression of the data.

Sue Baker

----- Original Message -----
From: Bale, Dan <mailto:D.Bale@handleman.com>
To: midrange-l@midrange.com <mailto:midrange-l@midrange.com>
Sent: Tuesday, August 14, 2001 12:57 AM
Subject: USEOPTBLK effect on which drives?

Can someone point me in the direction of the appropriate documentation that tells me whether USEOPTBLK(*yes) is effective on a 7208 model 012 tape drive on a V3R7 system?

Does USEOPTBLK(*YES) do any compression? The help text doesn't really say anything except that it may offer a performance benefit. I wondered about compression since USEOPTBLK(*YES) and DTACPR(*YES) cannot be used together.

If I'm tight on tape space and I've got plenty of time, would my better option be to use USEOPTBLK(*NO) and DTACPR(*YES)???

Thanks!

Dan Bale
Handleman Company