Thread (26 messages) 26 messages, 10 authors, 2007-12-30

Re: Linux RAID Partition Offset 63 cylinders / 30% performance hit?

From: Justin Piszcz <hidden>
Date: 2007-12-19 15:04:10


On Wed, 19 Dec 2007, Mattias Wadenstein wrote:
On Wed, 19 Dec 2007, Justin Piszcz wrote:
quoted
------

Now to my setup / question:

# fdisk -l /dev/sdc

Disk /dev/sdc: 150.0 GB, 150039945216 bytes
255 heads, 63 sectors/track, 18241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x5667c24a

  Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       18241   146520801   fd  Linux raid 
autodetect

---

If I use 10-disk RAID5 with 1024 KiB stripe, what would be the correct 
start and end size if I wanted to make sure the RAID5 was stripe aligned?

Or is there a better way to do this, does parted handle this situation 
better?
quoted
From that setup it seems simple, scrap the partition table and use the 
disk device for raid. This is what we do for all data storage disks (hw raid) 
and sw raid members.

/Mattias Wadenstein
Is there any downside to doing that?  I remember when I had to take my 
machine apart for a BIOS downgrade when I plugged in the sata devices 
again I did not plug them back in the same order, everything worked of 
course but when I ran LILO it said it was not part of the RAID set, 
because /dev/sda had become /dev/sdg and overwrote the MBR on the disk, if 
I had not used partitions here, I'd have lost (or more of the drives) due 
to a bad LILO run?

Justin.
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