SLUG Mailing List Archives
Re: [SLUG] hot swapping hard drives
- To: Adrian Chadd <adrian@xxxxxxxxxxxxxxx>
- Subject: Re: [SLUG] hot swapping hard drives
- From: Grahame Kelly <grahame@xxxxxxxxxxxxxx>
- Date: Sat, 16 May 2009 14:38:26 +1000
- Cc: slug@xxxxxxxxxxx
Hi Adrian, David & Slug list.
Of the seven systems I look after, three have hot-swapping HDA's via
a RAID5/6 drive enclosures, two systems have add-on SATAII caddies for
hot-swap and the others are without hot-swapping.
If your interested, and to reset your angst a little, I have been in
the computing/engineering industry for 25++ years.
On the software level the OS only has to ensure that all dirty
(written too) memory pages are written out to the drives and such
buffering flushed, drive index tables updated and written ALL before
the drive is removed. The CLI command "umount" does this within the
Linux / Unix OS. The "sync" command/programming API call is another
way to do this programmatically. That is all that is required.
On the hardware side, the PSU socket must ensure that power is
presented to the drive before logic is connected (ground first). This
is why the +12v, +5v and GND pins are usually extended about 8mm
before the rest of the pins are connected. On the logic side, logic
ground is the mandatory the first pin-out that is connected, together
with any design "reset" or "set" pins. Additionally, the ability of
the PSU to cope with demanding surges especially on +12v, +5V lines is
very important, as the switching regulator may be upset by such
demands. Most people wouldn't know this - that is why I mention it.
Of course, by all means - investigate and be satisfied your got all
the facts, its your system that will have to "cope" with any hot-
swapping PSU and logic levels.
On 16/05/2009, at 2:06 PM, Adrian Chadd wrote:
Uhm, I'm reasonably sure there's more to hot swap than the physical
and electrical connections.
I'd thus do a little more research on the topic (like reading the
datasheet(s) for your motherboard and SATA chipset) to ensure that
the hardware supports it.
There also may be a requirement for you to manually tell the OS
to "detach" and "attach" disk devices.
On Sat, May 16, 2009, Grahame Kelly wrote:
As long as the drive in un-mounted you can safely remove/insert a
device. You just need to make sure the drive Power connections allow
hot-swapping, but generally you will get away with it normally if you
haven't such PSU plug h/w. Just be aware that your PSU will require
better "surge" power - so if your current PSU is a bit iffy, it will
probably fail in time has been my experience.
Hope this helps.
From: david <david@xxxxxxxxxxxxx>
Date: 15 May 2009 11:58:14 PM
Subject: [SLUG] hot swapping hard drives
I've just installed a sata hard drive bay for a second drive, the
kind that has a little front door so you can slip the drive in and
The point of installing it was to make it easy to change drives when
doing backups, but I had assumed that I would have to shut down
before taking the drive in or out.
When I unmount it, Gnome announces that I can now remove the media,
which surprised me a bit. Should I assume that this means I can
safely hot swap this drive as long as it's unmounted? The nice man
in the shop assured me that I needed all sorts of mobo magic to be
able to do that, but of course he was talking Windows. I would hate
to splat 500G of backup.
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