MDADM: Full usefull ‘Cheat Sheet’

Mdadm is the modern tool most Linux distributions use these days to manage software RAID arrays; in the past raidtools was the tool we have used for this. This cheat sheet will show the most common usages of mdadm to manage software raid arrays; it assumes you have a good understanding of software RAID and Linux in general, and it will just explain the commands line usage of mdadm. The examples bellow use RAID1, but they can be adapted for any RAID level the Linux kernel driver supports.

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Intel Raid Controller RS2BL040 Slow Performance – BBU problems.

Just for the record:

When BBU is not exists, the default cache policy is no cache. So, forcing it to use even BBU not present helped in that case the fsync value goes up to above 3000. There are still lower fsync values and jumping speed values, but now these are much better than before.
Summary: BBU is recommended using a system like this.

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Align partitions for best performance using parted

There are two common problems when creating partitions in Linux on big storage arrays. The first is easy, and the warning message from fdisk is a bit of a giveaway:

WARNING: The size of this disk is 8.0 TB (7970004230144 bytes).
DOS partition table format can not be used on drives for volumes
larger than (2199023255040 bytes) for 512-byte sectors. Use parted(1) and GUID 
partition table format (GPT).

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