Zitat von Alan Brown <ajb2 AT mssl.ucl.ac DOT uk>:

> On 20/08/12 16:29, lst_hoe02 AT kwsoft DOT de wrote:
>> Hello List
>>
>> this has been discussed already some times on the list but as i have
>> ssen no real conclusion i will ask for opinion again. The setup is
>> Bacula 5.2.10 on Ubuntu 12.04 LTS (x64) with a LTO-4 drive connected
>> through Adaptec 29320LPE, a 320MByte/sec PCI-Express controller. To
>> prevent the LTO-4 tape from shining/whining around we use the Data
>> spool feature on a SSD drive (Intel Postville Refresh 120GB) with
>> "Maximum Spool Size = 20GB" and "Maximum File Size = 4GB". This works
>> as expected beside the fact that the transfer spped max. out at
>> ~84MBytes/sec with encrypted data (hard to further compress) and
>> 86MBytes/sec without encryption when using Bacula. To test if the
>> hardware is to blame i have done some simple dd to tape like this
>>
>> "dd if=/some/file of=/dev/nst0 bs=xxK"
>
> Test the speed of writing to/from disk as well as your tape speeds.
>
> SSDs have high IOPS/seek rates but they're not always as fast for  
> sequential operations as you might expect.

That's why i have done the "dd" tests from the same "disk" which yield  
the 140MBytes/sec. Other tests with hdparm/bonnie and simple cp yield  
to something in the line of 260MBytes/sec which looks like the Sata-2  
transfer limit. So saturating the tape speed should be possible, no?

Regards

Andreas





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