Disk 100% busy

[Brad Knowles]

At 1:34 PM -0500 2005-11-03, Francisco wrote:

>  On Mon, 17 Oct 2005, Brad Knowles wrote:
>
>>  	Note that RAID-1 is the second worst-case for mail server performance --
>>  it accelerates reads (if you have mirror load-balancing), but all writes
>>  are required to be held until complete on both disks.  The only worse
>>  case would be RAID-5, where you have to write (or re-write) an entire
>>  RAID block at once, plus the parity information.
>
>  Coming late into the thread...
>  What is a good raid level for a maildir IMAP server? RAID 10 (or 0+1 as
>  others call it).

	Yes, RAID 1+0 is generally considered to be the best.

	But keep in mind that you always want to stripe the mirrors and 
not mirror the stripes.  If you do the former, then if one of the 
disks die then the mirror is broken but the stripe is still okay.  If 
you do the latter, then if a disk dies then the stripe is broken, and 
then the mirror is also broken.

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.