Best use for FW drive

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Best use for FW drive

Post by shuman » Sat Jan 12, 2013 6:44 pm

I have a FW 400 enclosure housing a 160GB HDD that I have laying around. It gets better throughput than my USB drives, but is too small for home directory. Questions regarding best use:

What type of cache device will give me the best results to help improve performance?
What happens, in a panic situation, if there isn't redundancy on the cache device?
Can the cache device later be removed if I need to?
Could the same device be used for both read and write cache?
In your opinion, is there a better use for a drive like this?

Thanks,

Shuman
- Mac Mini (Late 2012), 10.8.5, 16GB memory, pool - 2 Mirrored 3TB USB 3.0 External Drives
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Thoughts

Post by grahamperrin » Sun Jan 13, 2013 6:01 pm

ZFS Data Loss Scenarios, in particular the accepted answer.

Impact of L2ARC cache device failure (Nexenta)

L2ARC

Here with a USB flash drive as L2ARC for my home directory (gjp22), ZEVO seems suitability resilient to planned and unplanned work without that drive. For planned work without that drive, I either:

  1. start the Mac without the drive; or
  2. in Terminal, use a macro for the required command (below) before disconnection:

Code: Select all
zpool offline gjp22 GPTE_64F61AFF-9EBC-4661-9520-7803CD1B8EE4


Taking the L2ARC part of the pool offline is easy enough.

Absolute removal from the pool, I don't know.

ZIL

From what I read, it seems advisable to be more careful with ZIL. Don't simply pull the plug, and so on.

The 160 GB hard disk drive on FireWire 400

I don't imagine that L2ARC or ZIL will be a good use.

If it's a few years old, accept the likelihood of not using it for much longer.

I have a FireWire 800 hard disk drive that's showing its age … occasional errors when scrubbed - but so far, not enough for me to throw it away. I set copies=2 and use it for Time Machine backups of data that is not mission critical. A permanent error might affect a band in the sparse bundle disk image that's written by Time Machine, but before long that band will probably be 'demoted' to ZFS snapshot level. That's far from best practice, but for me it's a realistic use of old hardware that I don't want to add to a larger pool. YMMV.
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