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April 10, 2019

Wayback Wed: Sizable drives for 3000s

Supersize
Ten years ago this month, we celebrated the fact that Hewlett-Packard created a forward-looking feature for the HP 3000 before its lab retired. One of the biggest enhancements gave MPE/iX the ability to use drives sized up to 512GB. Getting this size of drive to work involves going outside of the 3000's foundation, both literally as well as strategically.

External disc drives supply any storage beyond the 73GB devices which were fitted inside the HP 3000 chassis. This Hewlett-Packard part, numbered A6727A, was an off-the-cuff answer from Client Systems to the "how big" question. Client Systems built HP 3000s with this part installed while the company was North America's only 3000 distributor. But nothing bigger ever came off a factory line before HP stopped building 3000s in 2003.

Outside of HP's official channel, however, a drive twice as large has been installed on a N-Class with a pair of 146GB drives inside. The Seagate ST3146855LC spins at 15,000 RPM, too, a faster rate than anything HP ever put in a 3000. These Seagates are still available; just $95 today at Amazon.

Older 3000s, however, need single-ended drives for internal use. Allegro's Donna Hofmeister says the 3000's drive size limit is controlled by two factors: internal versus external, and HP "blessed," or off-the-shelf specified.

Hofmeister came to her work at Allegro from Longs Drug, and said the Longs systems accessed disk clusters, called LUNs, of many hundreds of GB.

When I was at Longs, I was able to effortlessly mount a very large LUN on one of my systems. I wish I could remember how big it actually was, but I reckon it must have been several hundred GBs. The LUN would have been comprised of many physical mechanisms -- but the system never saw that level of detail.

The "blessed" question was debated from the late '90s onward between HP engineers and 3000 consultants and veterans. HP would only support disc devices that passed its extraordinary reliability tests. Nobody was surprised that only HP-branded discs ever got this blessing for the 3000. Once disk storage got inexpensive, drives from the same manufacturers who sourced to HP gained a following with the veterans.

"There’s the whole supported/blessed/holy aspect to the question," Hofmeister said. "[The Client Systems] answer is technically correct. On the other hand, my current favorite MPE system to torture has a 400-plus GB drive attached to it, and it works great. I certainly wouldn’t classify this disc as falling into the supported/blessed/holy category."

HP released patches to MPE/iX 7.5 to make this possible. The project the vendor called "Large Disk" gives 3000 users "the ability to initialize an MPE/iX disk volume of up to 512 GB on SCSI-2 compliant disks. SCSI-2 Disks that are larger than 512GB will be truncated at the 512GB limit and the space beyond 512GB will not be usable by the MPE/iX Operating System or any user applications running under MPE."

HP started the engineering to release the patches for the 6.5 and 7.0 versions of MPE/iX, but never finished testing for those versions of MPE/iX. The 7.5 patches are

MPEMXT1        FSCHECK.MPEXL.TELESUP
MPEMXT2        [ALT|LIST|NEW][ACCT|GROUP]
MPEMXT3        SCSI Disk Driver Update
MPEMXT4        SSM Optimization (>87GB)
MPEMXT7        DISCFREE.PUB.SYS
MPEMXU3        REPORT
MPEMXU6        CATALOG.PUB.SYS
MPEMXU7        CIERR.PUB.SYS, CICATERR.PUB.SYS

HP sold a disk of 300GB that might qualify for "blessing" if the labs had ever put the device through the 3000 tests. But the vendor has always erred on the side of caution about larger drives, even in an era when disk had become cheaper than $2 a GB. HP's Jim Hawkins offered a white paper on Large Disk that advised caution for using 3000 disks larger than 36GB.

MPE/iX transaction throughput increases when MPE is allowed to spread IO across disks. Even though newer disks are faster than older disks, there are limits to disk speed and bus speed which must be taken into account. Moving from, say, nine 2GB disks to one 18GB disk will often create a Disk IO bottleneck. For best performance we recommend that the number of MPE LDEVs never be reduced -- if one has nine 2GB disks then they should be replaced with nine 18GB disks to ensure no loss of throughput.

HP never did support the full drive bus speed for the larger disks. 3000s get only Ultra-160 throughput, while HP-UX supported Ultra-320 on the very same devices.

The larger disks offer a significant value over the blessed drives. It's important to order a parallel SCSI version (LC) when purchasing a drive. SAS drives replaced the LC drives and cost much less.

05:04 PM in History, Homesteading | Permalink

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