Date: Thu, 2 Jul 1998 13:48:26 +0200 (MET DST) From: Willem Jan Withagen <wjw@surf.IAE.nl> To: scsi@FreeBSD.ORG Subject: Using a DPT controller, pros and cons Message-ID: <199807021148.NAA23248@surf.IAE.nl>
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Hi,
We're and ISP with way to many disks.....
So once in a while we have some crashes, nothing new.
To overcome the trouble with replacing disks, we monitor the amount of
entries in the reallocation tables in the disks. This doesn't always work,
but if the number starts growing you'd better replace the disk.
The other solution we want to migrate to is RAID, since it'll reduce the
downtime in case of a fatal crash where we'd need to replace a disk and
restore the data. (Which takes forever, if customers are calling avery 5
minutes)
The remainder of the story below is waht is preventing us to go to
the DPT solution, and I'd like to hear other peoples experience with this.
So we have a hardware RAID-box (DTC controller) which we are testing
here at work with 12*4Gb in 2 RAID-5's.
At home I have a DPT-controller which at the has:
RAID-5 with 3*2Gb with 2GB hotswap, on a narrow bus.
on the wide bus:
RAID-5 with 4*4Gb
RAID-1 with 2*4Gb
1*4Gb hotswap
I finally got this to work at 5 Mhz, but that'll due to the cableing. That
is currently not the most important issue.
During the creation of these arrays, not everything went smoothly. And thus
rebuilds were fequent. My main problem is that once there is the slightes
hickup, the RAID is invalidated. And you have no chance of telling the box
that it was your failure. Now there are some DOS tools, but you'd have to
remember that we wanted RAID's to prevent downtimes in the first place.
[[ One thing I'd have to say:
I never had FreeBSD-stable crash while booting when there was a
rebuild. Note that I have the bootdisk on a measly IDE.
]]
BUT what I really missed are any applications to be able to figure out what
the RAID is doing. ALL I see is that the controller and the drive LEDs are
on. Other than that: nothing is known.
Simon has promissed that ASAP he'll make some applications which will allow
us to get more control over our RAID's
Would any pressure from clients persuade DPT to at least release some code
which would give us some dptmgr functionality????
The other issue:
I've done 3 'dd if=/dev/zero of=/mnt?/bar' in parallel on the
system.
2 go to the DPT RAID-1 and RAID-5
1 goes to a seperate MICROPOLIS on the onboard ahc0 contoller.
Now the MICROPOLIS get a sustained write stream of something like 2.7
Mb/sec. The two RAID's do not stream the data at all. There's seconds of
time where either of the disks doesn't take any data. Then one disk has,
like 5Mb/sec, and the other 0-4 blocks/sec.
(And this get worse if rebuild are on the way)
All in all something I would not expect.
the DPT contoller: 3334UW with 32Mb firmware 07L0
other hardware:
ASUS 55TP4S
bootdisk conner IDE 540 Mb
on ahc0: cdrom, dat-tape, mo, micropolis 4.3 Gb
DEC de0 10Mb ethernet
ATI Mach 2Mb video
and in the logs I find things like:
dpt0 ERROR: Marking 246407 (Write (10) [6.1.18]) on c0b0t12u0
as late after 17711004usec
dpt0 ERROR: Marking 246409 (Write (10) [6.1.18]) on c0b0t12u0
as late after 17739244usec
dpt0: Salvaging Tx 246378 from the jaws of destruction (10000/18149777)
dpt0: Salvaging Tx 246380 from the jaws of destruction (10000/18205091)
--WjW
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