Re: Practical maximums (was Re: PostgreSQL theoretical

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Scott Marlowe wrote:
> On Mon, 2006-08-07 at 16:09, Ron Johnson wrote:
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>> Scott Marlowe wrote:
>>> On Mon, 2006-08-07 at 15:18, Ron Johnson wrote:
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>>>> Scott Marlowe wrote:
>>>>> Oh, I see where you were headed.
>>>>>
>>>>> I've found a bit here and there googling about for multiplex and tar,
>>>>> and found an IO:Multiplex module for perl.
>>>>>
>>>>> I don't see why someone couldn't make use of it to create some kind of
>>>>> system where you'd do:
>>>>>
>>>>> pg_dump dbname | perl mulitiplexscript device1,device2,device3,devicen
>>>>>
>>>>> No need for postgresql to support it directly. Restoring would likewise
>>>>> just be a reverse operation.
>>>> Interesting. Many thanks. Scary though that it hasn't been touched
>>>> in 30 months.
>>>>
>>>> With multiple SCSI cards, each with it's own tape drive, this
>>>> immensely speeds up the backup operation.
>>> Yeah, I read the description, and I think it's just a fancy name for
>>> tee. sigh. Not REAL multiplexing, but stream duplication.
>> This is where a multi-threaded pg_tapedump would be more effective,
>> since it would be able to, for example, have 4 threads reading
>> (different parts of) the database and writing to 4 separate tape drives.
>
> Actually, I kinda prefer the idea of creating multiple streams using
> something like RAID, where if you have two streams, it's a mirror, if
> you have three or more then you rotate around a parity stripe like RAID
> 5. Then, any error on any one tape drive could be recovered. Veritas
> has something like that for tape drives.
>
> Heck, the more I think about it, the more I think it would be an
> interesting project for a device driver that was like /dev/mdt or
> something, and re-used the md libs from the hard drive universe.
>
> Attach X tape drive, put in a bunch of tapes, and just pg_dump > mdt0
> and you're backing up. Restore the other way around.

Tape RAID? I like that!!!!

If the disk system can keep the tape system full, though.

- --
Ron Johnson, Jr.
Jefferson LA USA

Is "common sense" really valid?
For example, it is "common sense" to white-power racists that
whites are superior to blacks, and that those with brown skins
are mud people.
However, that "common sense" is obviously wrong.
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