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pourpain's avatar
pourpain
Aspirant
Jun 08, 2019

X-Raid or Raid-5

I am resurrecting an old NV+ V1, with four 2TB drives.

Since I can never expand beyond this, it seems there's no benefit in X-Raid flexibility.  Should I let it use X-Raid by default, or choose Flex Raid-5?  NAS is used for PC backups, and video streaming.  It is also backed up and stored offsite.

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  • StephenB's avatar
    StephenB
    Guru - Experienced User

    pourpain wrote:

    Since I can never expand beyond this, it seems there's no benefit in X-Raid flexibility.  Should I let it use X-Raid by default, or choose Flex Raid-5?  


    It doesn't matter, as the underlying RAID mode will be identical.  XRAID is easier to set up (no need to over-ride the RAID mode via RAIDar), so you might as well just use that.

    • pourpain's avatar
      pourpain
      Aspirant

      Thank you.  I have read in a few places (unofficial, not in the documentation) that X-Raid uses Raid 4.  They also say that it is slightly better for sequential reads.  I assume in practice it might not matter (this unit is not fast enough to make any difference?).

      • StephenB's avatar
        StephenB
        Guru - Experienced User

        pourpain wrote:

        Thank you.  I have read in a few places (unofficial, not in the documentation) that X-Raid uses Raid 4.  They also say that it is slightly better for sequential reads.  I assume in practice it might not matter (this unit is not fast enough to make any difference?).


        The v1 ReadyNAS (sparc-processor systems) all use a dedicated parity disk - which is technically RAID-4.  But it's labeled as RAID-5 in FlexRAID.  So the on-disk structures are exactly the same.

         

        Newer ReadyNAS systems (4.2.x, 5.3.x, 6.x) all distribute the parity blocks across the drives in the array (which is normal RAID-5).

         

        As far as performance goes, RAID-5 distributes writes evenly across the disks.  With RAID-4, the partity disk needs to be updated for every write.  That increases wear on that disk, and also can become a performance bottleneck.  Though with the v1 NAS, the performance bottleneck is the CPU speed and memory in the NAS (not surprising in a 15-20 year old hardware design).