Slow Read Performance

I’m on a Mac Pro Nehalem using Mac OS X 10.6.2 in 64 bit kernel mode. I have 4 WD drives installed. Two 2TB drives and two 500GB drives. This slow READ performance still happens after a fresh ERASE with less than 1% of the volume used. Today sent a trouble ticket in with log file. On a FW800 connection the read speed is around 49.5MB/s.

DroboPro Firmware: 1.1.4
Drobo Dashboard: 1.6.7
Connection: iSCSI directly to Mac Pro Nehalem ethernet port with the cable provided
Incident #: 100116-000015

iSCSI settings: Automatically configure
IP Address:
Subnet Mask:

NIC settings: DHCP
IP Address:
Subnet Mask:

Flow Control:
Configure: Manually
Speed 1000baseT
Duples: full-duplex
MTU: Standard

You didn’t say how your Mac is connected to the DroboPro - iSCSI?

Yes it is connected via iSCSI. On a FW800 connection the read speed is around 49.5MB/s

Is it connected using a dedicated ethernet port on your Mac or via a network hub/switch?

It is connected directly to the Mac Pro Nehalem.

Did some troubleshooting today with the DroboPro connected via iSCSI directly to my MacBook Pro. In 64 bit kernel mode was still getting slow READ performance of around 3MB/sec. Reverted back to 32 bit kernel mode and the READ speed jumped to over 75MB/sec. My understanding is that Drobo Dashboard 1.6.6 and later fully support OS X 64-bit mode.


So what is going on with READ performance in OS X 64-bit mode?

Do you have another iSCSI target you can test? That would help to determine if it’s a Drobo-specific or an iSCSI on 64-bit Mac OS thing.

No I do not have another iSCSI target device. I would hope the good people at Drobo in charge of testing (are there people in charge of testing?) would be aware of a 64 bit Mac iSCSI issue… be it either a problem on the Mac end or their end.

I have reset the drobo pro and copied the data back to it (unfortunately many times under 1.1.4). Still slow read performance. Please understand that the slow read is only happening while booting into 64 bit kernel mode. The Drobo works perfectly in 32 bit mode. Shouldn’t that indicate the source of the problem? While using 64 bit kernel it’s the READ speed that is slow not the write.

Do you have a support case open then?

I honestly have not heard of this problem before.

Hello Andrae -

I’m a Sr. Level-3 Support Enginner at DRI.

I apologize for these issues: the 64-bit-specific nature of the problem is quite interesting.

Of course, I will investigate this issue as thoroughly as possible.

Please contact me as soon as possible with the following info:

  1. Corresponding console logs and system logs while testing Pro in 64-bit mode
  2. Diagnostics from the DroboPro captured shortly after running at least 15 minutes of read tests (64-bit)
  3. System Profiler data highlighting host spec, configuration, etc.

Note my email:

Thank you very much for your time and patience.

Steven Ponder
Sr. Level-3 Support Engineer
Data Robotics Inc.
(408) 567-3161

Yes I do as posted in the first post of this thread with incident number.

Will do Sir… conducting the 15 minute read test right now.