[Beowulf] Re: OT: LTO Ultrium (3) throughput?

[David Mathog]

Steve Cousins <cousins at umit.maine.edu> wrote
> David Mathog wrote:
> > Just under 60MB/sec seems to be the maximum tape transport read/write
> > limit.  Pretty reliably the first write from the beginning of tape was a
> > bit slower than writes started further into the tape.
> 
> I believe LTO-3 is rated at 80 MB/sec without compression. Testing it on 
> our HP unit in an Overland library I get:
> 
> WRITE:
> 
> dd if=/dev/zero of=/dev/nst0 bs=512k count=10k
> 10240+0 records in
> 10240+0 records out
> 5368709120 bytes (5.4 GB) copied, 71.8723 seconds, 74.7 MB/s
> 
> READ:
> 
> dd of=/dev/null if=/dev/nst0 bs=512k count=10k
> 10240+0 records in
> 10240+0 records out
> 5368709120 bytes (5.4 GB) copied, 69.2487 seconds, 77.5 MB/s

Rats.

I wonder what the difference is now? If you don't already have it,
please grab a copy of Exabyte's ltoTool from here:

http://www.exabyte.com/support/online/downloads/downloads.cfm?did=1344&prod_id=581

% /usr/local/src/ltotool/ltoTool -C 1 /dev/nst0
ltoTool V4.63  --  Copyright (c) 1996-2006, Exabyte Corp.

Tape Drive identified as LTO3(HP)
Enabling compression...OK

Done

% /usr/local/src/ltotool/ltoTool -i /dev/nst0
ltoTool V4.63  --  Copyright (c) 1996-2006, Exabyte Corp.

Tape Drive identified as LTO3(HP)
/dev/nst0 - Vendor    : HP              
/dev/nst0 - Product ID: Ultrium 3-SCSI  
/dev/nst0 - Firmware  : D21D
/dev/nst0 - Serialnum : HU10708TGG

% dd if=/dev/zero of=/dev/nst0 bs=512k count=10k
10240+0 records in
10240+0 records out
5368709120 bytes (5.4 GB) copied, 38.6474 s, 139 MB/s

% /usr/local/src/ltotool/ltoTool -C 0 /dev/nst0
ltoTool V4.63  --  Copyright (c) 1996-2006, Exabyte Corp.

Tape Drive identified as LTO3(HP)
Disabling compression...OK

Done
% dd if=/dev/zero of=/dev/nst0 bs=512k count=10k
10240+0 records in
10240+0 records out
5368709120 bytes (5.4 GB) copied, 91.9329 s, 58.4 MB/s

Done


So mine is not as fast as yours in the exact same test.  HP's LTT
tool shows an LTO 3 cartridge in the drive.  (Does this drive even
work with an LTO 2 or LTO 4?)

% ulimit
unlimited
% uname -a
2.6.24-19-generic #1 SMP Wed Jun 4 15:10:52 UTC 2008 x86_64 GNU/Linux
% cat /etc/issue
Ubuntu 8.04 \n \l

The system has 24 GB of RAM, dual Opteron 2218, and no cpufreq
adjustment running (the BIOS on this one does not support power
adjustment).  The relevant SCSI messages from the last boot 
in /var/log/messages are:

scsi6 : Adaptec AIC79XX PCI-X SCSI HBA DRIVER, Rev 3.0
	<Adaptec 29320LPE PCIe Ultra320 SCSI adapter>
	aic7901: Ultra320 Wide Channel A, SCSI Id=7,PCI-X 101-133Mhz, 512 SCBs
scsi 6:0:4:0: Sequential-Access HP	 Ultrium 3-SCSI   D21D PQ: 0 ANSI: 3
 target6:0:4: asynchronous
scsi6:A:4:0: Tagged Queuing enabled.  Depth 32
 target6:0:4: Beginning Domain Validation
 target6:0:4: wide asynchronous
 target6:0:4: FAST-160 WIDE SCSI 320.0 MB/s DT IU RTI PCOMP (6.25 ns,
offset 64)
 target6:0:4: Domain Validation skipping write tests
 target6:0:4: Ending Domain Validation

The module driving the Adaptec is "aic79xx", apparently with no
special options configured anywhere for when it loads.

Not sure which kernel parameters are relevant (if any).

This is really unlikely to be relevant, but...

% dd --version
dd (coreutils) 6.10
Copyright (etc.)
% ldd `which dd`
	linux-vdso.so.1 =>  (0x00007fff08bfe000)
	librt.so.1 => /lib/librt.so.1 (0x00007fdd00779000)
	libc.so.6 => /lib/libc.so.6 (0x00007fdd00417000)
	libpthread.so.0 => /lib/libpthread.so.0 (0x00007fdd001fb000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fdd00982000)

Thanks,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech