Smartctl : Linux disk I/O scheduler is reseted back to default's CFQ

Got a weird issue recently, I'm monitoring my SSD's life time with smartctl + Zabbix and realized that my scheduler settings are reseted each time smartctl was executed !

 # echo noop > /sys/block/sda/queue/scheduler  
   
 # cat /sys/block/sda/queue/scheduler  
 [noop] anticipatory deadline cfq  
   
 # smartctl -A --device=sat+megaraid,0 /dev/sda  
 smartctl 5.43 2012-06-30 r3573 [x86_64-linux-2.6.32-358.23.2.el6.x86_64] (local build)  
 Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net  
 === START OF READ SMART DATA SECTION ===  
 ...  
 ...  
   
 # cat /sys/block/sda/queue/scheduler  
 noop anticipatory deadline [cfq]  

There is no real solution, but you can work around by specifying  the generic SCSI name i.e "sgX "instead of sdX.

 # echo noop > /sys/block/sda/queue/scheduler  
   
 # cat /sys/block/sda/queue/scheduler  
 [noop] anticipatory deadline cfq  
   
 # smartctl -A --device=sat+megaraid,0 /dev/sg0  
 smartctl 5.43 2012-06-30 r3573 [x86_64-linux-2.6.32-358.23.2.el6.x86_64] (local build)  
 Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net  
 === START OF READ SMART DATA SECTION ===  
 ...  
 ...  
   
 # cat /sys/block/sda/queue/scheduler  
  [noop] anticipatory deadline cfq 

And voila ! Problem not really solved but that does the job !

You can use sg_map (part of the sg3_utils package) to check the sdX -> sgX mappings :

 # sg_map -a  
 /dev/sg0 /dev/sda  
 /dev/sg1 /dev/sdb  
 /dev/sg2 /dev/scd0  

Choosing RAID Level / Stripe Size

Below interesting articles on how to choose your RAID level / stripe size.

Good litterature on RAID :
http://www.fccps.cz/download/adv/frr/hdd/hdd.html

RAID Level Explained :
http://www.techrepublic.com/blog/datacenter/choose-a-raid-level-that-works-for-you/3237

RAID Stripe Explained :
http://www.anandtech.com/show/788/5

RAID Benchmarks :
https://raid.wiki.kernel.org/index.php/Performance

RAID Calculator :
http://www.z-a-recovery.com/art-raid-estimator.htm

In any case, always plan your workload type (Read/Writes, Sequential/Random, Large/Small File, Number of concurrent access).

Omreport doesn't update disk rebuild progress

Had to replace a hard drive on a Dell Server and omreport rebuild progress got stuck at 1%.

The solution is to restart the srvadmin service :

 # srvadmin-services.sh restart  

This is quite dirty but it's the only solution I found. This also happened when I changed a PERC H700 battery.

Another way to check the rebuild process is to export log with omconfig :

 # omconfig storage controller action=exportlog controller=0  

This creates a /var/log/lsi_MMDD.log file, with the rebuild progress :

 03/09/13 22:07:51: EVT#13296-03/09/13 22:07:51: 99=Rebuild complete on VD 01/1  
 03/09/13 22:07:51: EVT#13297-03/09/13 22:07:51: 100=Rebuild complete on PD 05(e0x20/s5)  
 03/09/13 22:07:51: EVT#13298-03/09/13 22:07:51: 114=State change on PD 05(e0x20/s5) from REBUILD(14) to ONLINE(18)  
 03/09/13 22:07:51: EVT#13299-03/09/13 22:07:51: 81=State change on VD 01/1 from DEGRADED(2) to OPTIMAL(3)  
 03/09/13 22:07:51: EVT#13300-03/09/13 22:07:51: 249=VD 01/1 is now OPTIMAL  

Same thing for the battery learn cycle.

Hope that helps !