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RE: Questions about software RAID level 1 (how long should it take to sync, etc?)


I had similar problem few days ago - after numerous server restarts due to
many power outages, raid1 became faulty and had to resync. It initially run
is about 1MB/s. When I stopped one disk-intensive process, the speed bumped
to about 20-25MB/s and stayed that high for entire process (less than 3
hours). These are two 160GB SATA drives.
So the reason of slow sync is mainly other disk operation, which makes the
disks seek a lot and lowers transfer-rate.

  bYE, Marki

> -----Original Message-----
> From: Mike Garey [mailto:random51k@gmail.com] 
> Sent: Monday, April 03, 2006 11:54 PM
> To: debian-isp@lists.debian.org
> Subject: Questions about software RAID level 1 (how long 
> should it take to sync, etc?)
> I'm in the process of setting up a software RAID level 1 on 
> debian testing with two 160 gig drives on an Asus P4P800 
> motherboard with Intel Pentium 4 CPU 3.00GHz and 512 megs of 
> RAM.  I've been following the instructions in 
> /usr/share/doc/mdadm/rootraiddoc.97.html and have just issued 
> the command "mdadm --add /dev/md0 /dev/hda1" to add my 
> original debian installation to the RAID array (after already 
> having copied the contents of hda1 to hdc1, and then 
> rebooting from hdc1). 
> When I cat /proc/mdstat, I get the following:
> [>....................]  recovery =  4.9% (7907776/158577472) 
> finish=1533.5min speed=1636K/sec
> I'm curious about a few things:
> 1) does 25 hours seem like a reasonable amount of time for an 
> initial synchronization of two 160 gig drives?
> 2) would using a hardware card (such as a 3ware 7006-2 
> Parallel ATA RAID Controller) decrease the amount of time to sync?
> 3) will it take this long to synchronize the drives after, 
> say, a system crash (ie a hard reboot), or does it only take 
> 25 hours for the initial sync ?
> 4) If I do decide to switch to hardware RAID, will I be able 
> to use the same drives without a large 
> configuration/resyncrhonization process?
> 5) if hda1 contained the original root system, and hdc1 is 
> simply a copy of it (ie the drives are a mirror), why is it 
> taking 25 hours to "synchronize" the drives, aren't they 
> already sync'd?  Shouldn't this be a much faster process?
> Any help or suggestions are very much appreciated.  Thanks!
> Mike

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