brodie@moocow.uucp (Kent C. Brodie) (09/20/89)
A while ago, someone posted some "quoted" times for backing up to various
devices. These quotes had come from DEC. The device in question was
"how fast is a TK70 drive?" (compared to other tape devices).
Well, I have an excellent "benchmark" test, the results of which
follow.
In short, I must first summarize WHAT i backed up, and what our system
configuration is:
Disk to be backed up: RA81 contaning about 200,000 blocks of data
and over 15,000 files. (it's my uucp disk......)
How it was backed up: BACKUP/LOG/IMAGE DISKNAME TAPENAME:SAVESET/SAVE
Job was processed on a standard (prior=3) batch queue.
Devices backed up TO: TA78 at 6250, and a TK70 drive.
(note: TA78 is on a HSC50)
System Configuration: VAX 6320, 64MB, VMS V5.1-1, about 90 interactive
users were on at the time.
here's the accounting summary of the TA78 tape backup:
BRODIE job terminated at 19-SEP-1989 13:53:01.93
Accounting information:
Buffered I/O count: 33573 Peak working set size: 769
Direct I/O count: 63666 Peak page file size: 2703
Page faults: 633 Mounted volumes: 1
Charged CPU time: 0 00:13:00.24 Elapsed time: 0 00:46:15.17
.... and then here's the TK70 drive.
BRODIE job terminated at 19-SEP-1989 12:59:05.11
Accounting information:
Buffered I/O count: 32876 Peak working set size: 804
Direct I/O count: 62673 Peak page file size: 2703
Page faults: 614 Mounted volumes: 1
Charged CPU time: 0 00:12:56.10 Elapsed time: 0 01:46:05.53
Working set, page faults, and CPU time are all very close, however,
ELAPSED time is a little worse than I expected. The TA78 took 46 minutes,
the TK70 took an HOUR and 46 minutes. whoa.
I don't want to analyze this further, I'll let you all take a gander at the
stats. Now, I imagine if I were to do the same backup on ONE LARGE file,
that the elapsed time would be closer, but who knows?
-kent
--
Kent C. Brodie Systems Manager at Large - Medical College of WI
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"*DOOOOP*" -The Skipper {Gilligan's Island}Wherry@arkham.enet.dec.com (Brad Wherry) (09/20/89)
(...stuff deleted...) >>"how fast is a TK70 drive?" (compared to other tape devices). Faster than a TK50 slower than a tu81+ or especially a ta78/79 >> >>Well, I have an excellent "benchmark" test, the results of which >>follow. Just a thought, I think most benchmarks require that you have a fairly "controlled" environment. In the case you presenet I think most people's mileage will VARY greately. ie. You can't control 90 Interactive users. >> >>In short, I must first summarize WHAT i backed up, and what our system >>configuration is: >> >>Disk to be backed up: RA81 contaning about 200,000 blocks of data >> and over 15,000 files. (it's my uucp disk......) >> >>How it was backed up: BACKUP/LOG/IMAGE DISKNAME TAPENAME:SAVESET/SAVE >> Job was processed on a standard (prior=3) batch queue. Okay, you are using the default block size for backup (unless you have IMAGE or LOG defined as a symbol to equate to /image/block=xxxxx). If you try 32768 I think you will find that you performance will improve. Also, You should be using the /buffers=N (4 or 5 is a good number), especially with the TK70 (its a streaming tape drive). You should also remember that by using /log you are generating more IO's and those IO's don't actually get issued until BACKUP knows that the data is on the tape. >> >>Devices backed up TO: TA78 at 6250, and a TK70 drive. >> (note: TA78 is on a HSC50) Okay TA78 ~600 KB/sec TK70 ~250KB/Sec flat out doing dumps from memory. VMS 5.1-1 backup performance will be about ~400 KB/sec max. >> >>System Configuration: VAX 6320, 64MB, VMS V5.1-1, about 90 interactive >> users were on at the time. >> Well, letsee, 90 interactive users probably running at priority 4. So, should any of them do anything compute intensive in the least then the jobs in the priority 3 batch queue will SLLOOOWWW down. And, if there is anything in the batch queue itself which is running the both jobs will be competing for computes. YOUR MILEAGE WILL VARY A GREAT DEAL HERE. Try your benchmark during a quiet time on your system. >> >>here's the accounting summary of the TA78 tape backup: >> >> BRODIE job terminated at 19-SEP-1989 13:53:01.93 >> Accounting information: >> Buffered I/O count: 33573 Peak working set size: 769 >> Direct I/O count: 63666 Peak page file size: 2703 >> Page faults: 633 Mounted volumes: 1 >> Charged CPU time: 0 00:13:00.24 Elapsed time: 0 00:46:15.17 >> Okay, that means you are getting roughly ~38 KB/sec. Yech. I suspect that some of the interactive users WERE running compute-intensive jobs. >> >>.... and then here's the TK70 drive. >> >> BRODIE job terminated at 19-SEP-1989 12:59:05.11 >> Accounting information: >> Buffered I/O count: 32876 Peak working set size: 804 >> Direct I/O count: 62673 Peak page file size: 2703 >> Page faults: 614 Mounted volumes: 1 >> Charged CPU time: 0 00:12:56.10 Elapsed time: 0 01:46:05.53 >> >> hmmm...~13 KB/sec. Again not a very pretty number. >>Working set, page faults, and CPU time are all very close, however, >>ELAPSED time is a little worse than I expected. The TA78 took 46 minutes, >>the TK70 took an HOUR and 46 minutes. whoa. >> Well, CPU time should be consistent. Backup has to work over the same amount of data in each case. I think that if you ran your benchmark when there were no (or very few) interactive users and ran them at priority 4, and used a larger tape record, and had more IO's outstanding that things would improve. try this: $backup/image/buff=5/block=32768/log diskname: tapedrive:foo.bck/save Ideally you would can the log file, but it is nice to have. Just make sure that if you do /log it goes to a file NOT a terminal ('cause it will take forever then). This information has been brought to you as a public service announcement. No warranty is made by issuing this information. Use at your own risk. >>Kent C. Brodie Systems Manager at Large - Medical College of WI I like the system name moocow!!! -- brad wherry uucp ...!decwrl!starch.enet.dec.com!wherry inet wherry@starch.enet.dec.com tel 508.841.2571 (w) Ex ignorantia ad sapientiam; e luce ad tenebras. ***** Disclaimer ***** These Views are my own, NOT DIGITAL's and should be construed as a position by the company either as support or offical decree. They are provided for
Wherry@arkham.enet.dec.com (Brad Wherry) (09/21/89)
oops my first posting to this group and I make an error.
Okay TA78 ~600 KB/sec TK70 ~250KB/Sec flat out doing dumps from memory.
^^^^^^^^^^
should be: ~85 KB/Sec
250 KB/Sec is the throughput of a popular third-party tape drive. sorry 'bout
that folks.
--
brad wherry uucp ...!decwrl!starch.enet.dec.com!wherry
inet wherry@starch.enet.dec.com
tel 508.841.2571 (w)
Ex ignorantia ad sapientiam; e luce ad tenebras.