RAID-10 and 4 HDDs - how many HDDs can break without loosing data?
I want to set up RAID-10 on 4 400 GB drives, on a not-so powerful machine (600 MHz ARM, Thecus n4100) - to have a total of 800 GB storage, with some protection against a drive failure.
As the machine is not very powerful, I don't want to use RAID-5 nor RAID-6.
Previously, I would use RAID-0 on top of two RAID-1s:
----RAID0----
| |
RAID1 RAID1
| | | |
HDD1 HDD2 HDD3 HDD4With RAID-0 on top of RAID-1, with 4 drives, I would achieve:
- 100% chance of recovery if any single, one disk fails,
- 50% chance of recovery if any two disks fail.
Now with RAID-10 in the Linux kernel, what are my chances of recovering from a single and two disk failure?
RAID10 ------------------ | | | | HDD1 HDD2 HDD3 HDD4
Is it also 100% if one disk fails, and 50% if two disks fail?
Or perhaps, with 4 drives, RAID-10 can survive any 2 disks failure?
Signature · 2 lines
Tomasz Chmielewski http://wpkg.org
Quoted 7 lines · Tomasz Chmielewski
With RAID-0 on top of RAID-1, with 4 drives, I would achieve:
- 100% chance of recovery if any single, one disk fails,
- 50% chance of recovery if any two disks fail.Now with RAID-10 in the Linux kernel, what are my chances of recovering from a single and two disk failure?
Is it also 100% if one disk fails, and 50% if two disks fail?
if the number of copies is 2 yes
Quoted 1 line
Or perhaps, with 4 drives, RAID-10 can survive any 2 disks failure?
nope
note that with raid10 the number of copies for each stripe does not need to be a divisor of the number of drives.
e.g you can have 4 drives and 3 stripe copies.
in this case you are able to survive any 2 disk failure. but the usable space is DRIVE_SIZE * 1.33
L.
Signature · 6 lines
Luca Berra -- [email protected] Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN X AGAINST HTML MAIL / \