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Bad performance wasting tape and cpu


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Retrospect 8.2.399

PowerMac G5 Quad 4 x 2.5 GHz, OS 10.5.8, 6,5 GB RAM

PCI-e ATTO UL5D Ultra320 SCSI controller

HP Certance Ultrium LTO-2


Backup of local machine (SATA) to HP Certance Ultrium LTO-2 (SCSI)


Backup Performance observed: 250 - 950 MB/min.

CPU: ~ 100 %


The tape is stopping and starting every 5 seconds and the CPU stays around 100 %. It's slowly killing the tape drive mechanism and waste the CPU. I need to backup about 6 TB of data, but under such performance it is nonsense.


My experience with Retrospect dates back to the very beginning of this product in the early 90's and it used to be the best backup software. Is Retrospect still a serious product?


Is there any fix for such bad performance?


For what it's worth, I tried Bakbone Netvault in the same setup, which shows a much better performance of 1000 - 2400 MB/min and the tape streams almost constantly. Netvault isn't going to be my favorite piece of software and it will disappear from the machine, but it demonstrates the hardware is not the problem.



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What exact settings are you using for the backup?


Retrospect 8 (and 9) is designed for Intel Macs. Your Mac is almost 7 years old (introduced October 2005). It uses a big endian CPU and Intel little endian. So Retrospect on a G5 spends a lot of (CPU) time swapping bytes.


With a G5, try running Retrospect 6.1. It's native PowerPC.

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I installed 10.4 Tiger and 6.1.138, and even 6.0.204. The performance is the same, hardly going over 1 GB/minute, even when backing up large movie files.


The backup set is using hardware compression and no encryption. Backup of the local hard drive. All defaults. SATA HD is showing 100 MB/s in benchmark tests. SCSI termination and cable are all high quality. If there was a hardware or SCSI issue the performance should be a lot worse.


The tape drive should be able to stream 144 GB/h. For what it's worth, Netvault shows twice the performance than Retrospect on the same machine. The differences in Netvault is that the tape does not start and stop all the time. Unfortunately, Netvault is no solution for me.


Regarding PPC vs Intel: I previously ran 8.2 on a Mac Pro 2009, 8-core, Apple RAID card, using the same tape drive and SCSI controller. The performance was 10 - 30 % better, but still underperforming - the tape was also starting and stopping a lot, like every 5 - 10 seconds.


PPC or Intel is not the solution. The problem is the Retrospect software or tape driver. It looks to me like some buffering or performance problem inside Retrospect. I have to backup about 8 TB of data.

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