Why Not To Shout At Your Disk Array

Brendan Gregg of Sun's Fishworks lab has an interesting video demo up at YouTube demonstrating just how bad vibes, if expressed with sufficient volume in front of a rack full of disks, can cause a spike in disk latency. White noise, evidently, doesn't do them much harm. (Maybe they just feel awkward to get yelled at on camera.)

Why isn't this under idle?

[rolfwind]

It's been known for a long time vibrations are not good for discs (see notebooks). Even by early 90s music CDs had skip protection. If a disc skips, latency will of course momentarily increase. And with tolerances down even further, it's probably worse than back then.

In 10-15 years it won't matter anyway, almost everything will have SSD by then.

Re:JBODs?

[Anonymous Coward]

If you've got ZFS, why would you do JBOD?

A few reasons.

• If anything, I'd have figured you're more likely to setup a disk array as a JBOD with ZFS than (say) UFS. After all, you can get ZFS to do RAID0 for you (ZFS can probably also RAID1, but it's better to do that in hardware).
• Solaris-10 still supports non-ZFS filesystems (VxFS) which I imagine you'd still want to use in some circumstances.
• Their customers might be running an earlier version of SunOS/Solaris. He might simply be using DTrace to look at a customer bug-report from another prespective.
• Indeed, even though he's debugging in Solaris, the customers might not even be running Solaris. Sun hardware is really sweet and is supported on both Microsoft Windows and various distributions of Linux.
• And even if all the above reasons don't apply, using a JBOD is a good way of eliminating variables if you're trying to isolate/trace a potential hardware issue.

Re:JBODs?

[paulz42]

Sure, with ZFS JBODs are the preferred storage. Let ZFS do end-to-end management of the storage, from the file level to the raw disk blocks. That way it can do it's end-to-end error checking and possible correction. If you do RAID1 in hardware ( really just firmware in the storage box) you trust that software to detect all problems and correct them or report them. That software may not do checking to see if both branches of a mirror are correct and pass on bad data upstream. ZFS will detect this because of it's checksums, but it will not be able to correct this. If ZFS is doing the mirroring it will detect it and read the other mirror, if that checksum is ok, it will correct the error and continue.

Re:Secret Fact : Ultrasonic noise at low volumes !

[thogard]

You don't know too many greybeards do you? I'm surprised that modern drives are susceptible to ultrasonic under 80 khz but real old drives and drums were known to have problems with low audible frequency harmonics. A simple solution to this problem is stamp a butterfly like pattern in the arm of the head. The same thing works for power lines (which is what the small dumbbell looking things are near the insulators)

Re:Secret Fact : Ultrasonic noise at low volumes !

[NeutronCowboy]

Informative? Seriously? I hope this is some metamod effort at providing Karma... but just in case someone does take this seriously, I should take out a patent on this. That way, when Monster sells their butterfly-patterned head arms for 20K to audiophiles who don't like the lack of warmth in SSDs, I can get in on the racket.