Dahua HDCVI Série Manuel De L'utilisateur page 387

RAID Note
Level
the data in the first malfunction HDD is not complete,
system can not rebuild the data based on the first
damaged HDD. Now you need to use the second
malfunction HDD, usually you can get the all data again.
RAID5 ! RAID5 is a widely used RAID level. It needs to have at
least three HDDs. It has two aspects into consideration:
data security and HDD usage level. One malfunction HDD
does not terminate service since the data is reading from
the odd/even verification block. RAID5 is suitable for
archiving and users have high demands of the
performance and uninterrupted data access such as video
editor.
When data in one of the HDDs is damaged, system can
!
use the rest data and corresponding verification
information to restore the lost data on the newly replaced
HDD. Once another HDD is malfunction before the data be
rebuilt on the newly replaced HDD, all data in the RAID5
will lose permanently.
! About read/write performance, it is generally low since
each write operation needs to calculate and write
verification. But it has high read performance. Besides,
each stripe group of the RAID5 has one stripe to write
verification, all strips added together will use one physical
HDD. That is to say, the space of the RAID5 logical HDD
equals to all physical HDD space to minus one physical
HDD space.
RAID10 ! RAID1+0 is so called RAID10 standard. It integrates the
features of RAID0 and RAID1, which makes it has the
general advantages and disadvantages of RAID0 and
RAID1 together. So it is secure and of high speed.
! RAID10 shall at least consist of four HDDs. It has the extra
high speed of RAID0 and high data security level of RAID1.
But the HDD usage level is low. RAID10 is mainly for the
database of general small space but has high speed and
tolerance control level.
Actually, RAID10 is many groups of RAID1 to create
!
RAID0. For each RAID1 group, it can tolerate one HDD
offline. RAID10 is still valid if one HDD of the RAID1 group
is malfunction while the data in the rest HDD is good.
RAID10 is invalid once two HDDs of the one group of
RAID1 are damaged at the same time.
Manuel de l'utilisateur de l'enregistreur vidéo numérique HDCVI autonome
Min HDD
Needed
3
4
378