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Old 09-15-2006, 05:56 PM   #1
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hard disk device name

I have 2 SATA drives on Dell Poweredge 750 server. In the beginning, the hard disks device names were /dev/sda and /dev/sdb. After a tech did some server optimizations/hardening and some other changes, it became /dev/hdc and /dev/hdd.

After more than 1 year, the device names are now back to /dev/sda and /dev/sdb. My question is what effect this will have on the system. What do I need to update on the system, do I need to be worried? I'm paranoid that some scripts/programs will not work properly Please advise and shed some lights on this matter. Thank you in advance.
Old 09-15-2006, 07:26 PM   #2
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What kind of work was the tech doing -- adding/removing disk controllers? I would give him a call to discuss what happened recently that caused that unexpected change, and to express your concerns and get some clarification about the changes. Regardless, in terms of "impact", if I were in your shoes the two main concerns I'd have would be with your boot manager and your fstab. Although I obviously have no idea what kinds of scripts your organization might be using, normally you would not include specific device names; you'd simply be using directory names.

In any case, your boot manager (eg, lilo.conf or GRUB) will contain references to specific device names, as will your fstab file, and if the device names are changed that could have a negative impact if/when you are rebooting. To illustrate using a very basic example, suppose you originally had two drives in your machine, with the primary master (/dev/hda) containing the Linux system files and the primary slave (/dev/hdb) allocated to be a separate /home partition. In your fstab, there would be a line similar to
/dev/hdb1  /home  ... ... ...
However, if you were to move that drive to another position, say the secondary slave (/dev/hdd) and didn't update fstab, then obviously the physical configuration of your drives would be out of sync with the specs in fstab. Along those lines, if you were to add a third drive into the primary slave position (/dev/hdb) then whatever data existed in /dev/hdb1 would be mounted to /home, which would be undesirable.

Overall you might want to just run a simple
fdisk -l
(Note that's a lowercase "L") and compare it to the contents of your boot manager and fstab. As long as everything's in sync it should be OK. I'd really get in touch with that technician though to find out what kinds of changes he was making. Good luck with it
Old 09-15-2006, 07:55 PM   #3
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Those changes were done over a year ago, I couldn't trace back. I don't notice anything funky after the device named changed to /hdc and /hdd though (the first change). Well, this most recent change (the second one) back to the original device name (sda and sdb) was due to downgrading the kernel and fixing the poor SATA transfer speeds. Before the change, the disk read was only 6mbytes/sec, as reported by hdparm -Tt /dev/hdc.

The tech said he did changes to fstab and I saw him run ' fdisk -l ' according to the .bash_history file. My server is a typical webserver used with a few static and dynamic sites. Some scripts on the server are apf firewall with BFD, mod_security, snort, chkrookkit, apache, mysql, php, eaccelerator, hotsanic, rrdtool, mrtg, and other essential scripts. Does any scripts come to mind that may be affected by the device name change? Thanks.

Last edited by bytez; 09-15-2006 at 07:58 PM.


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