Re: [opensuse] Re: multi disk failures
On Wed, Dec 14, 2016 at 9:12 AM, Greg Freemyer <greg.freemyer@gmail.com> wrote:
On Wed, Dec 14, 2016 at 8:50 AM, Per Jessen <per@computer.org> wrote:
Greg Freemyer wrote:
On Wed, Dec 14, 2016 at 8:07 AM, Per Jessen <per@computer.org> wrote:
jdd wrote:
Le 14/12/2016 à 11:40, Per Jessen a écrit :
jdd wrote:
> my main concern on raid is unused data control, that is > verification of the integrity of unused data on disk (to prevent > unexpected multi disk failure).
Huh? You mean check unused data
data
or unused space? I don't see what you
would gain and I am not aware of any enterprise class hardware that will do it. Usually SMART (and other vendor-specific diagnostics) tests are run regularly, that's about it. If you cannot rely on your data being written accurately to your disk, all bets are off.
it's certainly a problem. I read recently a discussion about it (but don't remember the exect name):
loook at this
http://sysadmin1138.net/mt/blog/2012/12/how-multi-disk-failures-happen.shtml
Yes, multi disk failures definitely do happen, the risk increases with the drive size. That's why we use DRBD mirror copies, hot spares and RAID6, staged drive purchases, and make sure each array has a good mix of different drive ages.
Now you just need to mix in some surveillance disks :)
Haha - given that they intended for 100% duty cycle, I do see some interesting use cases. Problems I see - apparently they don't support hot-swap, and the 3-year warranty. Pro: they're about 2/3 the price of the WD RE and they have more cache.
Hot swap in a drive is normally implemented via pin length, right?
If so, I can inspect the pins and let you know.
Greg
(resending, apparently I had HTML enabled) I pulled the drives. They appear identical. Definitely the same metal chassis as viewed from the outside. In particular I looked at the length of the SATA connector pins. As expected some were longer than others. But the arrangement was identical on the Barracuda Pro and the Skyhawk. I guess everyone knows that the different lengths are used to control the order of pin connections. The longer pins make contact first on insertion and break contact last on removal. I believe the Skyhawk should be hot-swappable with no problem. That makes sense because the Skyhawk is said to have been engineered to work in a raid array. In part that means the vibration from a drive in the next bay should not have a major impact on the Skyhawk. I expect it to also include hotswap features. Greg -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
Greg Freemyer wrote:
I pulled the drives. They appear identical. Definitely the same metal chassis as viewed from the outside.
In particular I looked at the length of the SATA connector pins. As expected some were longer than others. But the arrangement was identical on the Barracuda Pro and the Skyhawk.
I guess everyone knows that the different lengths are used to control the order of pin connections. The longer pins make contact first on insertion and break contact last on removal.
I was not aware, I've never looked into it.
I believe the Skyhawk should be hot-swappable with no problem. That makes sense because the Skyhawk is said to have been engineered to work in a raid array. In part that means the vibration from a drive in the next bay should not have a major impact on the Skyhawk. I expect it to also include hotswap features.
According to my regular supplier (specs on their website), the Skyhawk is 7200rpm and not hot-swappable. Another supplier's website just links to the datasheet. One says 256Mb cache, another only 64Mb. -- Per Jessen, Zürich (1.5°C) http://www.dns24.ch/ - your free DNS host, made in Switzerland. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
On Wed, Dec 14, 2016 at 12:35 PM, Per Jessen <per@computer.org> wrote:
I pulled the drives. They appear identical. Definitely the same metal chassis as viewed from the outside.
In particular I looked at the length of the SATA connector pins. As expected some were longer than others. But the arrangement was identical on the Barracuda Pro and the Skyhawk.
I guess everyone knows that the different lengths are used to control the order of pin connections. The longer pins make contact first on insertion and break contact last on removal.
I was not aware, I've never looked into it.
Time to get out your magnifying glass! Actually I can see it without magnification. But it is much more obvious with the magnifying glass. In general the power pins are slightly longer on hotswap devices. That allows the overall circuitry to get powered up before the data lines are connected. I've seen it implemented on both the male and female part of the connector. With SATA it's the male connector on the drive that I just looked at. It is only a millisecond or two time difference, but apparently that is enough time to charge up the circuitry. Greg -- Greg Freemyer -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
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Per Jessen