[CentOS] Rescan /dev/sd* without reboot?

Rainer Duffner rainer at ultra-secure.de
Wed Jul 2 00:34:03 UTC 2008

Am 02.07.2008 um 00:17 schrieb John R Pierce:

> Joseph L. Casale wrote:
>>> This is an old way of doing it but it's worked fine for me over the
>>> years.
>> I think the new way is documented here:
>> http://www.linuxjournal.com/article/7321
> i've had very good luck with
> echo "- - -" > /sys/class/scsi_host/host?/scan
> replacing ? with the proper scsi/fiberchannel host channel #
> done this on online systems with minimal impact to other in-use  
> drives.

Personally, I find this a very sad state of affairs.
Why on earth is there no API to rescan the SCSI-bus (and the fabric)?

There's also Kurt Garloff's rescan-scsi-bus.sh script (haven't used  
it in a while and not on RHEL5).

FYI: In W2K3, you enlarge the LUN on the SAN, use diskpart.exe to  
enlarge the volume...and that's it!

I can't believe that nobody needs that in Linux-land.
If you enlarge the LUN on the SAN for a Linux-volume, you end-up with  
a 2nd partition behind the first - you'd need to do some nasty,  
dangerous disklabel-manipulations to fix that.
I end-up just adding another LUN and using LVM to piece them  
together. Of course, having multiple LUNs from a SAN in an LVM makes  
it next to impossible to create a consistent snapshot (via the SAN's  
snapshot functionality) in case the SAN (like all HP EVAs, AFAIK) can  
only do one snapshot of a LUN at exactly the same time.
(And lately, we use ZFS and a cheap MSA70 that eliminates most these  
inconveniences and happens to save a huge amount of money compared to  
a SAN from HP).

Rainer Duffner
rainer at ultra-secure.de

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