====== RAID ======
  * RAID0 - striping
  * RAID1 - mirror
  * RAID5
    * do not use
    * very slow write
    * rebuild takes days, and during rebuild another disk may fail = fatal
  * RAID6 - striping with double parity (5+2, 13+2).
    * minimum 4 disks
    * allow 2 disk failure
    * slower write than RAID5 (requires udpate parity on 2 disks)

Recommended levels for safety: 
  * RAID10 = RAID 1 + 0 = i.e two mirrors (RAID1) stripped as RAID0
  * RAID6
  * RAID60 = RAID 6 + 0 - two RAID6 sets stripped as RAID0

====== Raid controllers ======
  * controllers where RAID can be disabled, and all disks are exposed to host are called: ''HBA'', ''JBOD'', ''IT-MODE''
    * H200
    * H310 ???
    * PERC 6 (no ''i'' letter)

===== Dell =====


  * SAS1 - 3Gbps
    * SAS5E
      * SFF-8470 connector
      * supported by MD3000 (the same  SFF-8470 connector)
    * SAS6E
      * SFF-8088 connector

    * PERC 6
      * no memory
      * only JBOD, RAID0, RAID1
      * disks exposed to host
    * PERC 6i 
      * memory
      * 3Gbps connector, requires such midplane
      * no possibility to expose disks directly to host (trick is to create one RAID0 per disk)
    * PERC 6iR  (PERC 6 I/R)
  * H series - SAS2 - 6Gbps - different connectors comparing to SAS1
    * PERC H700
      * SAS2
      * SSD support
      * battery option
      * memory slot
      * must be inserter into dedicated PCI RAID slot
      * no possibility to expose disks directly to host (trick is to create one RAID0 per disk)
    * **H200**
      * **plain HBA**
      * no raid
      * JBOD - all disks exposed to host (so called IT-mode)
    * H310
      * **plain HBA**
    * H330
      * 8 internal ports
      * can be flashed into HBA [[https://forums.servethehome.com/index.php?threads/flash-crossflash-dell-h330-raid-card-to-hba330-12gbps-hba-it-firmware.25498/|Flash/Crossflash DELL H330 RAID Card to HBA330/12Gbps HBA IT Firmware]]


[[https://fohdeesha.com/docs/perc.html|H310/H710/H710P/H810 Mini & Full Size IT Crossflashing]]