120MB/s uncompressed. With a 2:1 compression ratio you're looking at 240MB/s to 
a single drive, in real life usually around 100-200MB/s. So if not all of your 
data is already compressed, encrypted or deduped a single LTO4 drive is limited 
by a one gigabit transport.

-km

On 12 feb 2013, at 20:38, Shawn DREW <shawn.drew AT US.BNPPARIBAS DOT COM> 
wrote:

> LTO4 is rated at 120MB/s max speed, which comes out to just under 1gbit/sec 
> (1gbit/s = 125MB/s).  I normally reserve 1gbit for each LTO4 drive.  (i.e. 4 
> drives on a 4gb HBA)
> I do see 110+MB/s streaming on those guys.  (using topas -T on AIX, so not 
> sure about the accuracy)
> 
> 
> Regards, 
> Shawn
> ________________________________
> Shawn Drew
>> -----Original Message-----
>> From: ADSM-L AT VM.MARIST DOT EDU [mailto:ADSM-L AT VM.MARIST DOT EDU]
>> Sent: Tuesday, February 12, 2013 12:04 PM
>> To: ADSM-L AT VM.MARIST DOT EDU
>> Subject: Re: [ADSM-L] 1 GBit FC sufficient for tape library?
>> 
>> Another thought:  You really want to avoid the LTO4 drives dropping out of
>> streaming mode, even if 1Gb/s is enough bandwidth to theoretically move
>> the amount of data you need to move.  I believe LTO4 will operate down to
>> 30-40MB/s.  Worth checking, since I'm not sure, but I'm pretty sure you can
>> drop as low as 40MB/s and still stay in streaming mode.  Once you drop out of
>> streaming mode, your throughput will go in the dumper, and you won't get
>> anything close to 1Gb/s throughput.
>> 
>> At 10:15 AM 2/12/2013, Michael Roesch wrote:
>>> Hi Stefan,
>>> 
>>> one quick question: what are the numbers you are using for your
>>> calculation?
>>> 
>>> Did you convert 240 MB/s into Gigabit/s?
>>> 
>>> Thanks
>>> 
>>> Regards,
>>> Michael
>>> 
>>> 
>>> 
>>> On Tue, Feb 12, 2013 at 1:01 PM, Stefan Folkerts
>>> <stefan.folkerts AT gmail DOT com>wrote:
>>> 
>>>> Yes, two LTO4 drives would not be happy at all behind a 1Gb/s HBA,
>>>> even two 1Gb/s HBA's are not enough to fully utilize the drives.
>>>> I would imagine you could also run into driver/firmware issues with
>>>> this combination since it's a very strange one but then again....it
>>>> would probably work just slow.
>>>> 
>>>> 
>>>> On Tue, Feb 12, 2013 at 12:34 PM, Michael Roesch
>>>> <michael.roesch AT gmail DOT com>wrote:
>>>> 
>>>>> Hi Stefan,
>>>>> 
>>>>> the drives are LTO4 ones. So the HBA would be the bottleneck
>>>>> 
>>>>> 
>>>>> On Tue, Feb 12, 2013 at 11:36 AM, Stefan Folkerts <
>>>>> stefan.folkerts AT gmail DOT com
>>>>>> wrote:
>>>>> 
>>>>>> If it is LTO1 or LTO2 you would be OK, if it is LTO3 or higher
>>>>>> you are limiting your drivers with your HBA.
>>>>>> 
>>>>>> 
>>>>>> On Tue, Feb 12, 2013 at 10:39 AM, Michael Roesch
>>>>>> <michael.roesch AT gmail DOT com>wrote:
>>>>>> 
>>>>>>> Hi all,
>>>>>>> 
>>>>>>> we have an old HP MSL 6030 with two drives that share one 1
>>>>>>> GBit FC
>>>>> port.
>>>>>>> Would that be enough to use with TSM? I have a feeling that says
>> "no"
>>>>>> but I
>>>>>>> couldn't find any minimum FC requirements.
>>>>>>> Anyone having more info? Maybe even an IBM technote?
>>>>>>> 
>>>>>>> Thanks
>>>>>>> 
>>>>>>> Regards,
>>>>>>> Michael Roesch
>> 
>> 
>> --
>> Paul Zarnowski                            Ph: 607-255-4757
>> CIT Infrastructure / Storage Services     Fx: 607-255-8521
>> 719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu
> 
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