Re: support for tape library sun sl24 or sun sl48

On 2009-05-18 16:28, Uwe Bartels wrote:

Hi,
does anybody know if the tape library sun(storagetek) sl24 orsun(storagetek) sl48 with 2 lto4 tape drives are working?
If so. how are the general parameters, which i'm missing in the "TapeType List <http://wiki.zmanda.com/index.php/Tapetype%20definitions> ".


http://wiki.zmanda.com/index.php/Tapetype_definitions#LTO4

Dell PowerVault LTO4-120 - LTO4-800 tape

define tapetype LTO4 {
   comment "Dell LTO4 800Gb - Compression Off"
   length 802816 mbytes
   filemark 0 kbytes
   speed 52616 kps
}

Arcvault 48 - HP LTO4-800 tape

define tapetype HPLTO4 {
   comment "HP LTO4 800gb - Compression Off"
   length 772096 mbytes
   filemark 0 kbytes
   speed 31368 kps
}


But I believe both of these entries have a speed that is indicating
the host cannot keep up with the speed of the tapedrives.

I believe the speed for LTO4 should be near 120Mbyte/second. And probably
(can't find the source where I learned about it) the tapedrive
can slow down to about 50% to the minimum streaming speed.
Below the minimum streaming speed the drive needs to stop/restart
and while doing that, it looses capacity, as you can see from the
length numbers above.  (And besides capacity loss, the wear/tear
on the tape and tapedrive becomes significant as well!)

So I would insert a tape in your drive, and run amtapetape on your
own configuration, to verify if your host is capable to drive the tape
at full speed.  Also take into consideration that amtapetype does
not even read the data from disk.  To be able to read the data at
at least 60Mbyte/sec from disk, you'll need a holdingdisk with a
striped raid setup.

--
Paul Bijnens, Xplanation Technology Services        Tel  +32 16 397.525
Interleuvenlaan 86, B-3001 Leuven, BELGIUM          Fax  +32 16 397.552
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