Is overlapping two RAID5 arrays on same drives a bad idea ?? Post: 302527862

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Operating Systems Linux Red Hat Is overlapping two RAID5 arrays on same drives a bad idea ?? Post 302527862 by mark54g on Sunday 5th of June 2011 11:47:33 PM

06-06-2011

Registered User

Larger files, on average, should have a larger chunk size, so that you can satisfy a small request with one drive, allowing alternate requests to be satisfied by other drives. I tested with things like fio, and bonnie++ to get results with the devices I was using and eventually settled on a 256K chunk size for my video collection, which is averaging 1GB per home movie.

For my /boot partition, I went with 8K, because the files are tiny. I tried 64K to 2MB chunk sizes, in various RAID flavors before settling on RAID 1E.

Also, your partition layout does not have to matter much when you are using RAID, albeit with a few exceptions. Your /boot volume cannot reside on a RAID 5 or 6. I believe only mirroring is currently supported.

Also, when I said a "Vanilla Kernel" I was not referring to a particular distribution called Vanilla, but rather, Vanilla has a connotation of being stock, plain, devoid of added things. You are using a kernel customized for xen, which you MAY want to do, but if you are not using xen currently, with only the possibility that you may wish to add it, I would boot a different kernel until such time that you really require xen (though I like KVM or VirtualBox now).

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LEARN ABOUT REDHAT

mkraid

mkraid(8)						      System Manager's Manual							 mkraid(8)

NAME

       mkraid - initializes/upgrades RAID device arrays

SYNOPSIS

       mkraid [--configfile] [--version] [--force]	     [--upgrade] [-cvfu] </dev/md?>+

DESCRIPTION

       mkraid  sets  up  a  set of block devices into a single RAID array.  It looks in its configuration file for the md devices mentioned on the
       command line, and initializes those arrays.  mkraid works for all types of RAID arrays (RAID1, RAID4, RAID5, LINEAR and RAID0).

       Note that initializing RAID devices destroys all of the data on the consituent devices.

OPTIONS

       -c, --configfile filename
	      Use filename as the configuration file (/etc/raidtab is used by default).

       -f, --force
	      Initialize the consituent devices, even if they appear to have data on them already.

       -h, --help
	      Displays a short usage message, then exits.

       -o, --upgrade
	      This option upgrades older arrays to the current kernel's RAID version, without destroying data. Although the utility detects  vari-
	      ous pitfalls like mixed up disks and inconsistent superblocks, this option should be used with care.

       -V, --version
	      Displays a short version message, then exits.

NOTES

       The  raidtools  are  derived from the md-tools and raidtools packages, which were originally written by Marc Zyngier, Miguel de Icaza, Gadi
       Oxman, Bradley Ward Allen, and Ingo Molnar.

BUGS

       Probably many.

SEE ALSO

       raidtab(5), raidstart(8), raid0run(8), raidstop(8)

																	 mkraid(8)