Yes, adding more discs will improve disc I/O, subject to all
the usual disclaimers. Once out start getting more than 4 or 5 discs
on a controller, the improvement will be less noticable. Adding another
controller or two would really help (but finding a place to put that
controller can be a problem.)

If you don't unload and reload the system, your existing files will
stay where they are, and only new files will appear on new drives,
so you might not see any improvement.

Adding more memory will improve the performace of your disc,
because more will be cached, and less actualt disc I/O performed.
With memory pretty cheap, adding another gigabyte is a reasonable
thing to do. You might even see a little more cpu time free 
as it spends less time managing limited memory.

On 9x9 series, they come with 1 built-in FWD SCSI, and have 2 full length
expansion slots available so 2 more can be added. On the smaller, non HP989
machines, you can add 2 more full-length slots inside the main chassis
by buying the appropriate upgrade. The HP989 allows up to 6 processors,
and this interferes with adding more SCSI inside the box.

To add more slots, you need to add an expensive (but pretty cheap used)
I/O expansion upgrade, that plugs into the HSC, and then provided
a PB convertor and 7 more slots. However, since everything is running 
through this 32mb/second PB bus, I doubt you can effectively run more
than a few more SCSI channels.

The real shame is that the HSC (100mb interface to memory) is supported
under Unix for SCSI interfaces, and 4 interfaces fit in the HSC!!
Under MPE, you have to plug a slow 32mb adapter into the HSC,
and then buy an expensive box to plug slower SCSI cards into.
All this because they never got round to writing the driver for
the Unix flavor of SCSI card  :-(

Bottom line: adding more spindles helps, often a great deal.
But adding them to a new controller would help even more.
Don't forget to reload or something to spread your existing files
around. Try not to have too many drives on the same controller
(15 is the hardware limit, but I would try and stay at 8 or less
if at all possible. Remember that ldev 1, the system disc,
gets hit pretty hard, so try not to load up too many devices on it.

Also, it you add a DLT7000 or 8000, you need another dedicated SCSI
channel for it! This can really run up the price, but DLTs are certainly
better than DDS in terms of reliability.

I am sure the group will correct me if I am wrong about any of this.



-----Original Message-----
From: LES BUREAUX DE CRÉDIT DU NORD INC [mailto:[log in to unmask]]
Sent: Monday, January 22, 2001 11:37 AM
To: [log in to unmask]
Subject: [HP3000-L] Any rule of thumb to determine if transient free
space can be a bottleneck?


I have 3% transient free space used on LDEV 1 and 2 combined i.e. approx :
174 Mbytes.  I'm currious to know if transient free space can be an io
bottleneck.  If it is a major bottleneck, I'm thinking of using a ramdisk
and divert 100% transient space to the ram disk.

I have 2 disks for system volumes and 8 for private volumes split on 2 scsi
FW channels.   I'm also thinking of adding 5 more 10RPM disks to improve
disk striping.  Will more spindles really improve io bottleneck?

Comments?


Jean Huot
Northern Credit Bureaus Inc.
(819) 762-4351