Re: LTO4 vs LTO3 speed

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Paul,

How long ago did you move to the saving SAVFs?

Reason I ask, I worked on a system that originally did that.  But after a
couple of upgrades, it was faster to save directly to tape.

Its a smaller box, so it only has 8 disks.  So the limiting factor isn't
really the tape, it's the disks.  Reading and writing to the same set was
slower than streaming to the tape directly.

Charles


On Fri, Jun 14, 2013 at 5:11 PM, Musselman, Paul <
pmusselman@xxxxxxxxxxxxxxxx> wrote:

> Have you looked at what kinds of things you're saving?  Lots of little
> things take more time to write to tape than a few big things!
>
> We needed to structure our backups more efficiently, so we changed saves
> of some of the system stuff-- outqs, journals, configuration, history logs,
> security data, etc. to use SAVFs in a "SAVF Library."  We then saved the
> library to tape.  The save was much quicker.  "Much" is purely subjective--
> I don't have hard numbers-- but the difference was noticeable.  Instead of
> several hundred individual QHST files, it's 1 SAVF.
>
> Our main goal was more efficient use of our tape drives.  Saving to SAVFs
> took jobs that ran "quite a while" collecting data, and a little time
> writing to tape, and moved the 'collecting' to 4AM, while the writing was
> still with our evening backups.  The write of the library to tape takes
> about 10 minutes, while the individual saves can each take 10 minutes.
>  We're trading disk space for tape time.
>
> Another piece of anecdotal data--  the contract on our tape library was up
> for renewal, and we were considering moving from LTO-4 to LTO-5.  The
> difference in speed wasn't that impressive; the capacity was nice, but not
> Earth-shattering.  And if we continued to use our vast collection of LTO-4
> tapes, we wouldn't see any of the increase in speed or capacity.  Since our
> daily backups fit on LTO-4 tapes with LOTS of room to spare, we kept the
> LTO-4 drives.  They are 'fast enough.'
>
> Paul E Musselman
> PaulMmn@xxxxxxxxxxxxxxxxxxxx
>
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