[ale] hdparm and RAID cards

[JLightner at dsservices.com (Lightner, Jeffrey)]

Most of the MegaRaid cards I?ve seen are made by LSI/Avago (including the Dell PERC/SAS which are OEMed from LSI/Avago).

During POST when it find the BIOS of these cards it usually gives you a Ctrl-R option to go into that for config.   I don?t know whether that config allows you to change individual drive cache setup.   Typically I don?t muck with such setups on the assumption the card was already optimized.    I?ve only used it for creating/modifying the RAID layout.

Once they?re in a RAID presented by the card you?re not going to see the individual drives at OS level ? you?ll just see the entire RAID set(s) as individual drive(s).   e.g. If you had created a RAID1 of 2 disks for OS then a RAID5 for remaining disks you?re only going to see /dev/sda and /dev/sdb at OS level.


From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Jim Kinney
Sent: Friday, September 02, 2016 4:13 PM
To: Atlanta Linux Enthusiasts - Yes! We run Linux!
Subject: [ale] hdparm and RAID cards

How the $(^*#!!! do I use hdparm to enable write caching on a giant pile of drives that make up a hardware RAID 6 array?

I can peek through the controller with smartctl for health monitoring. The RAID controller (MegaRAID) has a tool to see that each drive has a N/A status for hardware cache (these drives all have a large multi-MB cache).

I _really_ don't want to have to convert all 28 drives to RAID0 so I can get a /dev/sdx node for hdparm.

--

James P. Kinney III



Every time you stop a school, you will have to build a jail. What you

gain at one end you lose at the other. It's like feeding a dog on his

own tail. It won't fatten the dog.

- Speech 11/23/1900 Mark Twain



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