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LTO Library Automation vs Standalone Drive?
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Here’s my SAN i/o during a write I’m running at the moment…
I’m curious as to why are there periods where the speeds aren’t reaching full speed?
I understand that the drive will slow down when writing lots of small files (vs large files), but this pattern is clearly cyclical and repetitive in nature so it doesn’t look like it’s related to the file sizes.
There is no other activity on my SAN at all today apart from this tape write.
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That’s a good question James. I ditched archiving from anything except directly attached thunderbolt RAIDs to remove storage from the list of potential culprits.
I’m starting to agree more and more with David–the whole chain for tape storage is just unreliable, and for me it started with LTO-6 (and automation). I’ve done a lot of troubleshooting over the years but LTO takes the cake by a long shot. Currently listening to one of the drives revving up and down, write speed dropping well below that of the other drive, when all day yesterday the exact same configuration (same exact type of data on the same source drive) cruised right along and finished at top expected speed. I don’t know what else that kind of behavior could point to beyond an unreliable system at the core.
I’d love to be proven wrong but its been an almost daily battle for two years with nothing even resembling an explanation or solution.
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Dan, here’s what my drive sounds like when it’s in “slow mode”.
This is a write operation. 100 GB of RED rushes being pulled from 2 x USB 3.0 G-Drives in RAID 0 (BM disk speed test says 322 MB/s write and 326 MB/s read).
I aborted the write then tried again, worked better with less clicking but still an oscillation between about half and full speed as per my SAN graph.
Doing some more testing but if it’s anything like the issues I’ve been seeing if I reverify this exact tape multiple times I will get average verify times for the complete data set ranging from 20 MB/s to 180 MB/s.
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Not exactly the same, but similar sounds from a base-level perspective. When the drives are acting properly in the library, they make the same constant sound for sustained periods of time–many minutes straight if not longer. When they aren’t working properly, its very clear because the spinning/whining noise of productivity slows to a halt, sometimes makes the knocking/clacking sound which seems like something is physically repositioning, and then starts whining again before repeating the aforementioned events. Or, it’ll just keep whining up and down over periods of a few seconds without the clacking. That’s when its really reading/writing slowly.
It’s been working properly for the last two days but I’ll nab a sound recording next time it inevitably starts screwing up again. But yeah, similar but different noises.
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And the lack of reliability continues. Had an 8TB archive job complete the write and get through 4.3TB of the verify, and all of a sudden one of the drives decides it doesn’t want to do its job anymore. Back to the revving up and verifying a tiny chunk of data, revving down to a halt. Up, down, up, down. This machine really just picks and chooses when it wants to work. Here’s a sound bite, you can hear the revving behind the fan noise and the noise of the other drive actually doing what its supposed to.
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Dan,
At Magnext we specialize in tape library repair and refurbishment. I saw you mentioning that your tapes were being marked full early on, this is usually a software related issue rather than hardware.
What software and library are you using when you’re experiencing these issues? Also, when you start getting slow downs and such, are you writing the files from a network source or a local disk/raid etc. ?
Tim Gerhard
Magnext
614-433-0011 x114
tgerhard@magnext.com -
Thanks Tim, I’m getting my tapes marked full early in BRU PE but I’ve heard of others in the business getting the same behavior with Archiware P5. Its very inconsistent and seems to come in waves. I only write archives from locally attached thunderbolt raids that can easily handle the speeds of 2x LTO-6 drives.
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