anecdotes about the SansDigital TR4U

In early 2008 I purchased my 6th SATA drive for my house fileserver. That chassis does not have the mount points for that many hard drives, so they are arrayed on the desk in front of the case with a 120mm fan blowing across them to keep them cool. I am also not confident of the ability of the power supply to keep them all running correctly.

To solve this problem I purchased a SansDigital TR4U external chassis. It has bays for 4 SATA drives and a single USB connection. This means that you have to enable the "Proble all LUNs on each SCSI device" option in your kernel SCSI options.

chemmis:517 $ gunzip < /proc/config.gz | grep SCSI_MULTI_LUN CONFIG_SCSI_MULTI_LUN=y

If you only see a single drive you have either configured the chassis for JBOD (super bad idea) or you didn't compile your kernel with SCSI_MULTI_LUN.

I picked the 4 smallest drives in my collection and pvmoved the data around until I could do a vgsplit to separate the 4 drives destined for the TR4U from the drives and data that would remain "in" the house fileserver. I then placed the drives into the external chassis and attached it to my MythTV backend, which became responsible for serving those DVD volumes via NFS.

problems

The case has a built-in fan, but I suspect it is inadequate. During operation the drives become hot enough that I could only hold my fingers on them for 5-10 seconds before I decided it was a bad idea. I have worked around this problem using a USB-powered fan (an otherwise useless device invented for gadget freaks) pointed at the front of the drives.

The TR4U is incompatible with my ancient house fileserver. Attempting to copy any significant quantity of data onto it causes the entire computer to lock up. Attaching the TR4U to my laptop or my MythTV server (its final home) works fine.

do not operate this thing in USB 1.1 mode

For the first year or more I owned this device I was connecting to it in USB 1.1 mode (max 12Mbit/s). I did a performance test and was able to get 7Mbit/s transfer rate.

Certain DVDs would stutter during playback. The problem ones appear to be very high bit-rate (two <30 minute episodes on a single DVD), while more densely packed DVDS (four or 5 episodes) played back fine.

When I recompiled my kernel with the EHCI driver I was able to get more than 130Mbit/s out of it.

thoth@alexandria /homes8/dvds/Invader_Zim/Zim-2/VIDEO_TS $ dd if=VTS_02_1.VOB bs=1024k of=/dev/null count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 6.12419 s, 17.1 MB/s