data transfer stutter

[sdw999]

Hi Forum,

I'm running my first test backup. My MBPro laptop is both server and client - i.e. a standalone machine. No tape. I'm testing a backup from internal SSD to a USB HDD and activity monitor clearly shows regular gaps/pauses/stutter where no I/O is occurring. Is there a performance setting that I can change to tell Retrospect to just run as quickly as possible, and not to continually pause? I have tested the drive, it is capable of sustained multi-gigabyte 30 MB/s sequential read and also same for writes.

Thanks,

Dave.

[Lennart_T]

I have tested the drive, it is capable of sustained multi-gigabyte 30 MB/s sequential read and also same for writes.

That is what you should get when backing up a single huge file. Most files are (very) small and that takes time. There is a lot of metadata to be gathered for each and every file, along with the actual data.

I bet you have over half a million files on your internal drive. Am I correct?

[sdw999]

In the past I have regularly used Ghost 15 to perform a VSS snapshot backup of 360 GB (from a 500 GB SSD) on a running Windows XP laptop (i.e. not booted in to the product, just normal WinXP) to an eSATA external 2.5" 7200rpm 500 GB HDD, and it would always completely fill the eSATA rev.1 channel at 150 MB/s, to backup that 360 GB in 41 minutes. So I was kind of hoping that Retrospect 9 would at least be able to sequentially fill the USB 2 bus to a 5400 rpm HDD. I'm not moaning, just curious about the stutter and lack of sequential streaming. If that's how it works, then so be it. I have about 50k files on the internal Mac drive that I'm testing.

[Lennart_T]

Ghost performs a "sector copy". Ghost copies the 360GB as one large chunk of data. You get ALL or NOTHING.

 

Retrospect performs a file copy, copying each file individually. That means you can select which files you want to copy. You can apply filters to filter out cache files, for instance.

 

To rephrase what I wrote before: One large chunk of data is copied much faster than half a million individual files. EDIT: OK, I saw now you have "only" 50000 files, but you get the idea...

 

Besides, you wrote "backup" in your first post. A "backup" in Retrospect parlance is different from a "duplicate". A backup has a "media set" as its destination. (A media set can have disk volumes as "members".) You can run several backups (in sequence) to the same destination (=media set) and be able to restore from any of the backups. A "duplicate" copies all files to a destination volume, erasing any older files residing there. So you can only retrieve the latest files, not an older version of a file, or a file deleted just prior to the last duplicate. Ghost would perform a "duplicate" in Retrospect's parlance.

 

So, are you performing a "backup" or a "duplicate"? In the latter case, please consider "Carbon Copy Cloner" or "SuperDuper". Retrospect is designed foremost for running backups, not duplicates. "Carbon Copy Cloner" and "SuperDuper" are designed for doing "duplicates".

[sdw999]

Thanks for the prompt replies Lennart.

 

The source disk read issue is not limited to Retrospect. It also happens for two other backup/duplication products that I'm trailing, namely Time Machine and Memeo.

 

I've tried HFS+ and NTFS (via Paragon driver) as targets, but both have the same issue. So it must be source disk/file-system or O/S related. I've tried two different internal SSD source disks - same problem.

 

Anyone have any ideas why MacOSX would behave this way?

Does anyone else see this?

 

If not - then I assume something else that I have installed must be causing it - but I'm new to MacOSX and I don't know where to look.

I've never seen anything like this before on any O/S (OpenVMS, Solaris, linux, WinAll), or backup/duplication/cloning software, i.e. where software is able to read source disk fine for 2 to 10 minutes and stream to the target disk, and then nothing, it all goes quiet for 2 to 10 minutes. Most odd. The read/write duration and the delay duration both vary randomly from anything from 2 minutes to 10 minutes.

 

If I run any of several disk exercisers - these run fine on both source and target - but then these work on just one file. It's almost as if the file system has a problem processing a large amount of file reads - or OSX is detecting a large amount of file system reads and stepping in and pausing.

[Lennart_T]

I've never seen anything like this before on any O/S (OpenVMS, Solaris, linux, WinAll), or backup/duplication/cloning software, i.e. where software is able to read source disk fine for 2 to 10 minutes and stream to the target disk, and then nothing, it all goes quiet for 2 to 10 minutes.

MINUTES?????? Yikes!

What you described would be normal if we were talking seconds (or parts of seconds), where the transfer seems to stop a few tenths of a second every second (or every two seconds).

 

What you see is certainly not normal.

And from what you describe isn't a Retrospect problem.

 

 

Try a safe boot, then boot normally before trying again.

http://support.apple...iewlocale=en_US

http://support.apple.com/kb/ht1455

 

EDIT: Paragon is a known source of various problems. Try uninstall it completely. (There should be instructions with the software.)

[sdw999]

I totally agree - not a Retrospect problem.

 

I did have a second SSD in place of the SuperDrive (so a non-standard spec) - I've now put the SuperDrive back in.

 

Just tried copying the 35k files in finder - all good - sustained 50+ MB/s to a FW800 HDD with a 5400rpm drive.

I'll test the backup s/w again - I/O delays could have been caused by non-standard parts.

[Lennart_T]

Please keep us updated.