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RE: [ccp4bb]: SUMMARY - Backup devices
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Dear All,
Thanks for all the repsonses on this one.
This was my question:
--------------------------------
Dear All,
I am looking to purchase a backup system for use in the lab that will be
compatible with devices at Daresbury, Grenoble and Hamburg. I guess the
current favourite is DLT, but which flavour should I go for? There was much
discussion about Firewire disks a few weeks back, but how widely used are
these? I am slowly moving from SGs to PCs running Linux, so compatibility
with the latter would be preferred.
Any advice on makes/models, capacities, suppliers, and prices of both
devices and media would be most appreciated. Info on how these devices
connect to your computer would also be useful (e.g. SCSI).
Thanks very much in advance,
Dave Lawson
-----------------------------------
Here are the responses:
-----------------------------------
from Bernhard Rupp:
David, we are using small FireWire disks (80GB) at ALS to transport
our data. I think this is much faster and more reliable than DLT
(shelf life, mechanical problems etc etc). Ftp is out of the
question considering the image data amounts one tends to produce.
I would assume that other beamlines will follow and move to FW.
I am sure they will contact you as well.
best,BR
-----------------------------------------------------------------
Bernhard Rupp
Macromolecular Crystallography and Structural Genomics
LLNL-BBRP L448 Phone (925) 423-3273
University of California Phax (925) 424-3130
Livermore, CA 94551 email br@llnl.gov
URL http://www-structure.llnl.gov
TB Structural Genomics Consortium http://www.doe-mbi.ucla.edu/TB
EU Mirror http://www.ccp14.ac.uk/ccp/web-mirrors/llnlrupp
-----------------------------------------------------------------
from Peter Moody:
have you thought of dvds?
4.7Gb and re-usable > 1000 times.
I havn't tried it yet though, so I don't know how long it takes to write.
Cheaper and lighter than DLT, you can get a writer for 400 quid now.
(although I think firewire is the way to go)
Peter Moody Direct Line +44 (0)116 2523366
Department of Biochemistry FAX +44 (0)116 2523473
Adrian Building
University of Leicester Email pcem1@leicester.ac.uk
University Road
Leicester.
LE1 7RH
http://www.le.ac.uk/biochem/staff/pcem1/pcem1.html
X-ray lab http://www.le.ac.uk/by/pcem1/
------------------------------------------
from Robert Esnouf:
Hi David,
I'm sure you'll get lots of replies, but... there are different
flavours of both tapes and drives...
DLT-III tapes have a capacity of 10GB native and cost about £20
DLT-IV tapes have a capacity of either 20GB, 35GB or 40GB native and
cost about £40.
DLT4000 drives will read/write DLT-III and DLT-IV, but will only
write 20GB native to a DLT-IV. Nominally, you get double capacity
using compression giving a nominal 40GB on DLT-IV (hence DLT4000).
Likewise DLT7000 and DLT8000 drives will read/write DLT-III and
read/write 35/70GB and 40/80GB, resp., to DLT-IV tapes. You can also
tell DLT7000 and DLT8000 drives to read/write at lower density (e.g.
DLT4000).
In practice with xray data and our sort of backup I don't get
two-fold compression, more like 1.3:1 hence I get about 50-55GB
on a DLT-IV.
Now, DLT4000 and DLT7000 drives won't read data written at full
density on a DLT8000 drive. Additionally DLT4000 drives won't read
data written at DLT7000 density. So, of you want to buy a drive that
can import data from sites with either DLT7000 or DLT8000 then get a
DLT8000 drive. (Similarly if you are mainly concerned with exporting
then
a DLT7000 might be a better option.) DLT8000 are about £2500.
To stir into this mess there is a 'cheap' form of DLT drive called
DLT1 (about £1500). I have no experience of their compatibility. Also
there is a newly emerging tape standard called super DLT (sDLT). These
have
a capacity of 110GB native (220 compressed) and are up to 3x faster.
In addition, an sDLT drive will read DLT-IV tapes (in all densities,
I think). These drives aren't cheap at about £3500 but might be
a good compromise for getting data in and backing up quickly. sDLT
tapes are expensive at about £120. I'm not sure of the availability
of Linux drivers for these.
Alteratively, a totally different linear tape technology is emerging
called Linear Tape Open (LTO) and the HP variant is called Ultrium.
Currently these are similar in speed and capacity to sDLT but they
are a bit cheaper (under £100 each) and the signs are that LTO might
be the long term winner. There are plans to get up to 2TB per tape!
DLTs tend to be connected with LVD differential SCSI (in whatever
wide/ultra flavour) they are quite demanding drives so you will
probably have a dedicated controller for the device. These aren't
very expensive. Makes of DLT are mainly Quantum or rebadged... they
are the technology owners.
Regards,
Robert
--
Dr. Robert Esnouf, Division of Structural Biology,
The Henry Wellcome Building for Genomic Medicine,
Roosevelt Drive, Oxford OX3 7BN, UK
Emails: robert@strubi.ox.ac.uk Tel: (+44) - 1865 - 287560
and robert@esnouf.com Fax: (+44) - 1865 - 287547
-------------------------------------
from Mischa Machius:
Hi David,
You have certainly followed my rants against tape backup devices and
my favoring of firewire disks. They are clearly the fastest and most
convenient _BACKUP_ devices. Archiving is a different story. However,
any backup device will only be fool proof if you bring your own
laptop/computer to the beamline. There are so many different
standards for DAT, Exabyte, and DLT drives. You won't find technology
that is represented at all beamlines you are likely to go to. The
operating system they use might be different from the operating
system you use at home, which produces another hurdle. Another aspect
is that they probably don't have enough devices. E.g., we always make
double backups. Beamlines might have one particular tape drive, but
not two, which results in us struggling to get all the backups done
before we had to leave. That was another reason to switch to firewire
disks. If you decide to go with firewire, get good and stable disks
that are made for traveling. We have had problems with the cheap ones
that are only made for desktop use. One thing that I would recommend
over and in addition to all backup devices is to ftp your frames home
immediately where someone else can write them on tape/CD/DVD etc.
right away. In practice, for a while now, we haven't even touched our
firewire disks as all frames had been successfully ftped already.
Cheers,
Mischa
---------------------------------------------
from Manfred Baumstark:
Dear Dave,
all DLT drives are manufactured by the same company (Quantum), all others
are OEM. DLT-4000 is most widely available at the synchrotrons you
mentioned. The material of DLT tapes is either M (maxtor??) or F (fuji),
see the code on the back side. There are rumors that DLT-8000 does not
like switching between these two types of tapes. I was told this by our
computing center and indeed my DLT-8000 runs better (especially read
performance) since I exclusively use F tapes. For synchrotron trips we use
exclusively DLT-4000 (M and F mixed) with no problems at all.
For the migration SGI to Linux it might be intersting to know that SGI
offers
the XFS filesystem for Linux as open source project. There are kernel RPMS
for Redhat. ( http://oss.sgi.com/projects/xfs/ )
This is still a bit experimental, but I used a Linux notebook with an
external XFS formated SCSI disk recently to backup my data at the ESRF
(much better than FTP: "rsync": http://samba.anu.edu.au/rsync/index.html ).
At home I connected the disk to the SGI, rsync'ed to the main RAID, finish.
Manfred
P.S. To switch disks between IRIX and Linux I partitioned the disk under
IRIX and made the fs as advised by one of the developers:
> And make sure you specify version 2 directories and turn off unwritten
> extents, so:
>
> mkfs -d unwritten=0 -n version=2
>
> The default block size is 4K so that should be OK.
>
> Steve
---------------------------------------------
from Charlie Bond:
David,
We currently use an HP SureStore DLT40 attached (SCSI) to an O2. This
DLT-4000 technology is by no means the most current - it cost about
#1600 2 years ago (current price #1200?), will write 20Gb native (<40Gb
compressed). Unlike DAT, we have had no incompatibility/unreadable tape
problems with data from ESRF and DL.
The original drive did fail after 6 months, but as it was supplied with
a 3 year next-day replacement warranty, this caused no problems.
I have not tried the drive under Linux.
Cheers,
Charlie
--
Dr Charles S. Bond MSI/WTB Complex Tel: +44-1382-348325
BBSRC David Phillips Fellow Dow St. Dundee Fax: +44-1382-345764
School of Life Sciences DD1 5EH Scotland C.S.Bond@dundee.ac.uk
University of Dundee http://stein.bioch.dundee.ac.uk/~charlie
-------------------------------
-------------------------------
Dr. David M. Lawson
Biological Chemistry Dept.,
John Innes Centre,
Norwich,
NR4 7UH, UK.
Tel: +44-(0)1603-450725
Fax: +44-(0)1603-450018
Email: david.lawson@bbsrc.ac.uk
Web: http://www.jic.bbsrc.ac.uk/staff/david-lawson/index.htm