SDLT wear & tear (small files vs. big files)
 

Hello... I'm a storage newbie, so please forgive me if this is a
stupid question.

I've got a new StorageTek Library (L40) with an SDLT 320 drive in it.
I am using Veritas NetBackup DataCenter for Windows 2000.

My question has to do with wear and tear on the drive heads. My
previous library (also a STK, model Timberwolf 9730) experienced some
drive failures during its lifetime. I did a little reading and one of
the things that caught my eye was the additional wear & tear
introduced by writing many small files to the tape (I guess if it is
not a constant stream of data, the drive keeps spinning up and down).

One of the servers that I need to back up has hundreds of thousands of
small 1MB files. Will this sort of backup decrease the expected
lifespan of my drive? Does anyone know if Veritas takes this into
account and buffers the data to minimize this effect?

Any insight into the subject would be greatly appreciated. Thanks for
the help!


----
george sarlas

Hi there,

Veritas should handle this for you, Netbackup will ensure that the drive is
fed at a constant rate ... provided you feed the backup server a continuous
stream of data to write to tape. You could just ensure that when creating
you backup schedule maybe have the server with all the little files backing
up in parallel with some other servers ... what is SDLT about 30Mb/s ? So
maybe have 4 or 5 servers going to the same drive at the same time. Either
way Veritas should be able to sort it out with little to no tweeking (it's
why you've paid so much money for it :-)

Regards

Mark




"George Sarlas" wrote in message
om...
Hello... I'm a storage newbie, so please forgive me if this is a
stupid question.

I've got a new StorageTek Library (L40) with an SDLT 320 drive in it.
I am using Veritas NetBackup DataCenter for Windows 2000.

My question has to do with wear and tear on the drive heads. My
previous library (also a STK, model Timberwolf 9730) experienced some
drive failures during its lifetime. I did a little reading and one of
the things that caught my eye was the additional wear & tear
introduced by writing many small files to the tape (I guess if it is
not a constant stream of data, the drive keeps spinning up and down).

One of the servers that I need to back up has hundreds of thousands of
small 1MB files. Will this sort of backup decrease the expected
lifespan of my drive? Does anyone know if Veritas takes this into
account and buffers the data to minimize this effect?

Any insight into the subject would be greatly appreciated. Thanks for
the help!


----
george sarlas

In article ,
Mark wrote:
Veritas should handle this for you, Netbackup will ensure that the drive is
fed at a constant rate ... provided you feed the backup server a continuous
stream of data to write to tape.

*sigh*

Here one is with a multi-thousand-dollar tape drive, multi-hundred-dollar
backup software, and adding a cheap hard drive to the mix would let one
buffer up to dozens of gigabytes to keep the data flowing smoothly to the
tape.

So, the $64,000 question: will Netbackup allow you to do this? If so, it
seems like an obvious solution.

--
I've seen things you people can't imagine. Chimneysweeps on fire over the roofs
of London. I've watched kite-strings glitter in the sun at Hyde Park Gate. All
these things will be lost in time, like chalk-paintings in the rain. `-_-'
Time for your nap. | Peter da Silva | Har du kramat din varg, idag? 'U`

*sigh*

Here one is with a multi-thousand-dollar tape drive, multi-hundred-dollar
backup software, and adding a cheap hard drive to the mix would let one
buffer up to dozens of gigabytes to keep the data flowing smoothly to the
tape.

So, the $64,000 question: will Netbackup allow you to do this? If so, it
seems like an obvious solution.


I'm not sure if you are being helpful or not ? The original poster asked a
question, I gave what I think is a sensible answer.

Mark

In article , Peter da Silva ruminated:
In article ,
Mark wrote:
Veritas should handle this for you, Netbackup will ensure that the drive is
fed at a constant rate ... provided you feed the backup server a continuous
stream of data to write to tape.
Here one is with a multi-thousand-dollar tape drive, multi-hundred-dollar
backup software, and adding a cheap hard drive to the mix would let one
buffer up to dozens of gigabytes to keep the data flowing smoothly to the
tape.

So, the $64,000 question: will Netbackup allow you to do this?

No. Netbackup will, however, interleave multiple backups onto the tape in
order to keep it streaming. All you have to do is make sure you schedule the
backups such that other systems are backing up at the same time as this
system full of tiny little files.

--
Eric Lee Green
Linux/Unix/Storage Software Engineer seeks employment
see http://badtux.org for resume


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In article ,
Mark wrote:
I'm not sure if you are being helpful or not ? The original poster asked a
question, I gave what I think is a sensible answer.

I asked a question: can Netbackup use a local disk as cache to buffer tape
writes and prevent shoeshining?

--
I've seen things you people can't imagine. Chimneysweeps on fire over the roofs
of London. I've watched kite-strings glitter in the sun at Hyde Park Gate. All
these things will be lost in time, like chalk-paintings in the rain. `-_-'
Time for your nap. | Peter da Silva | Har du kramat din varg, idag? 'U`

"Peter da Silva" wrote in message
...
I asked a question: can Netbackup use a local disk as cache to buffer tape
writes and prevent shoeshining?

Only as a two-step process.
1) Backup from servers to disk
2) Disk-to-tape copy

So, it works, but does increase the amount of time it takes to complete
backups (though it may decrease the amount of time that the servers being
backed up are busy)

Scott

"Eric Lee Green" wrote in message
...

No. Netbackup will, however, interleave multiple backups onto the tape in
order to keep it streaming. All you have to do is make sure you schedule
the
backups such that other systems are backing up at the same time as this
system full of tiny little files.

--
Eric Lee Green
Linux/Unix/Storage Software Engineer seeks employment
see http://badtux.org for resume

Don't forget that multiplexed backups will slow down your restores. If you
sized your backup system properly (that is, in line with your restore
requirements..) then the introduction of multiplexed backups will require
you to recalculate your restore parameters. Eg. if you multiplexed 4 streams
to generate a 16MB/s data stream, your restores from a single stream will
never be faster than 4MB/s.

Rob

In article , Rob Turk ruminated:
"Eric Lee Green" wrote in message
...
No. Netbackup will, however, interleave multiple backups onto the tape in
order to keep it streaming. All you have to do is make sure you schedule
the
backups such that other systems are backing up at the same time as this
system full of tiny little files.


Don't forget that multiplexed backups will slow down your restores. If you
sized your backup system properly (that is, in line with your restore
requirements..) then the introduction of multiplexed backups will require
you to recalculate your restore parameters. Eg. if you multiplexed 4 streams
to generate a 16MB/s data stream, your restores from a single stream will
never be faster than 4MB/s.

Not exactly. It depends upon the multiplexing technology that you're using.
I don't know what NetBackup uses, but when I was working on the design for
SuperBru, I tagged each block of data sent to tape with a stream ID, and
interleaved data as it became available on the incoming sockets. Thus if
you had the situation you're talking about, what would end up happening
would be a situation where the system with tons of tiny little files would
restore at a maximum of 4mb/sec, and where the three other streams might
actually be sequenced such that each one could be restored at 12mb/sec.
Planning the timing for that interleave via a GUI interface was an exercise
left for another software engineer :-). (I don't do GUI's).

Staging is of course the other possibility. One concept I've recently
seen bandied about is a tape library that actually uses a hard drive
to simulate the library, and transparently stages to tape. The Hard
Question that hits me then is the issue of tape compression and making
sure that the data to be staged will actually fit on a given tape. I
can think of a couple of workarounds, but none that really satisfy me
yet. As far as staging of entire backups via backup software, if we're
talking about a small office network that may be satisfactory, but I'm
having difficulty conceiving how to handle terabyte-sized backups in a
reasonable manner that way.

--
Eric Lee Green
Linux/Unix Software Engineer seeks employment
see http://badtux.org for resume


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In article ,
Eric Lee Green wrote:
As far as staging of entire backups via backup software, if we're
talking about a small office network that may be satisfactory, but I'm
having difficulty conceiving how to handle terabyte-sized backups in a
reasonable manner that way.

Instead of interleaving the streams straight to tape, write them to disk.

When a stream is full, or you have a tapes worth, write to tape.

If one disk won't keep the tape happy, slice the stream across multiple
drives, either explicitly or using RAID.

--
I've seen things you people can't imagine. Chimneysweeps on fire over the roofs
of London. I've watched kite-strings glitter in the sun at Hyde Park Gate. All
these things will be lost in time, like chalk-paintings in the rain. `-_-'
Time for your nap. | Peter da Silva | Har du kramat din varg, idag? 'U`