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Old 10-14-2002, 03:10 AM   #1
Registered: Aug 2002
Location: Cape Town, South Africa
Distribution: Red Hat 8.0 (Home), Red Hat 8.0 (Work)
Posts: 388

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Can you have RAID 4 in Linux?

Supposedly one is able to set up RAID 4 in LInux, but when I do it and then cat the /proc/mdstat, I see RAID 5 active, with algorithm 0? What is actually going on, I mean I know that they are the same save for RAID 4 using one disk exclusively for parity, but what does the MD driver actually do? Does it implement it just like RAID 5, but with the different parity algorithm which stores parity on 1 disks only?

Does anyone have any info on this?
Old 10-14-2002, 04:06 PM   #2
Registered: Aug 2002
Location: Cape Town, South Africa
Distribution: Red Hat 8.0 (Home), Red Hat 8.0 (Work)
Posts: 388

Original Poster
Rep: Reputation: 30
OK, just an update in case anyone is interested (it doesn't seems so ).

The RAID 4 and RAID 5 give me exactly the same results. The sequential reads are very fast, reflecting the striping, and the sequential writes are about half of seq, writes, reflecting the fact that the parity needs to be calculated.

The one thing that bothers me, is that the writes should be a *little* faster. I am now in doubt whether the parity is being striped, or is only one disk being used for parity and that;s what's slowing down the writes.

Mcleodnine, you seem to know your stuff when it comes to RAID. What is your opinion on this?


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