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тАО06-03-2010 08:44 PM
тАО06-03-2010 08:44 PM
Backup is taking more time using LTO4 in HP MSL 8096
Thanks in advance
Badhusha
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тАО06-05-2010 03:16 AM
тАО06-05-2010 03:16 AM
Re: Backup is taking more time using LTO4 in HP MSL 8096
Your information is incomplete but let's try to help:
a) Did you install Library and Tape Tools to
check your setup?
b) What is the version of your HP-UX server?
c) What is the model of the LTO-4 tape
drive:
Ultrium 1760
Ultrium 1840
d) From memory, MSL 8096 with four LTO-4 1840 drives offers maximum sustained transfer rate (with 2:1 compression rate)
of around 3.4 TB/hour. That would mean
roughly around 0.85 TB/hour for a single
drive.
e) What is the software that copies
raw database to tape?
Cheers,
VK2COT
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тАО06-05-2010 09:02 AM
тАО06-05-2010 09:02 AM
Re: Backup is taking more time using LTO4 in HP MSL 8096
LTO1 = 15 MB/sec
LTO2 = 30 MB/sec
LTO3 = 60 MB/sec
LTO4 = 120 MB/sec
(LTO5 is faster but I'm having trouble locating the MB/sec so I'll guess at about 240 MB/sec)
So your LTO3 is performing quite well (or more accurately, your disk is sending data fast enough to keep the tape drive from slowing down). Starting with LTO3, a feature called Data Rate Matching was introduced to help with slow disks. DDS, DLT and older LTO drives cannot slow down -- they have only one speed. If the data doesn't come fast enough, the tape drive must halt, reverse direction, then pause to wait for more data to arrive. If the disk data rate is slightly less than than the tape drive, then these repositioning sequences can reduce throughput to 20%, even as bad as 5% of normal speed. Repositioning has an enormous effect on throughput and as you might expect, it wears the tape and the tape drive unnecessarily.
The fact that LTO4 seems to run at the same speed as LTO3 indicates that the disk simply isn't fast enough. For filesystem backup, high performance backup products will read 5 or 10 separate files at the same time to create a data stream fast enough for these modern tape drives. But a raw volume backup means a single data stream from the disk and multiple reader processes can't improve the data rate.
Now the backup software should be a high performance product designed for very high throughput. Improving the disk throughput requires analyzing all points along the data chain. For a JBOD disk, there is probably little you can do -- these tape drives exceed the sustained read rate of most disks. For a disk array, increasing the cache size won't help during backup as all the data being read will be new to the cache after a short time. Striping the disk LUNs will help immensely.
The interface speed (array to computer) should be a minimum of 2 Gbit and if a SAN fabric is in the middle, end-to-end performance of the fabric will be a concern. Then the computer interface should be maximized with multiple paths. This would have to be coordinated with the array capabilities and will require a path manager like PowerPath or HP-UX multi-pathing. Finally, a slow computer will prevent full speed.
Bill Hassell, sysadmin
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тАО06-07-2010 02:56 AM
тАО06-07-2010 02:56 AM
Re: Backup is taking more time using LTO4 in HP MSL 8096
# HP-UX cdsdrs B.11.23 U 9000/800 3450146013 unlimited-user license.
Media = HP LTO 4 ULTRIUM RW 1.6 TB C7974A
Backup S/W :- HP Software Dataprotector 6.0
Server is connected to library and EMC2 DMX4 storage with FC card(2GB).
I am not able to confirm 1760/1840
Regds
Badhusha
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тАО06-07-2010 04:23 AM
тАО06-07-2010 04:23 AM
Re: Backup is taking more time using LTO4 in HP MSL 8096
Are you sure you can read the data fast enought to feed the LTO?
you may use LTT and run the system performance test in order to identify is the cause of the bandwidht limitation is due to the source of the data