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Unable to create a LUSE in XP 24000 disk array

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BENABBOU
Advisor

Unable to create a LUSE in XP 24000 disk array

Hi guys
I'm about creating a LUSE containing 23 logical devices.
I have 22 logical devices from one parity group (RAID 6).

When i try to add the 23th logical device form an other parity group (RAID 5), i can't

there is any restriction to constitute a LUSE from difirrent Parity group ?

thnks in advance
5 REPLIES
IBaltay
Honored Contributor
Solution

Re: Unable to create a LUSE in XP 24000 disk array

Hi,
the idea of creating LUSE from 1PG is not a good idea. Its far better to create the LUSE from the different parity groups but the CU:LDEV must be above the master LUSE address.
From the perf point of view its better to create LUSE from max. of 8 members but preferably less. Better idea is the LDEV concatenation with interleaving - it can concatenate 4 7D+1P into 28D+4P PG, which is stripped. Then no LUSE but LDEV only could be created across those 32 HDDs in the PG.
the pain is one part of the reality
BENABBOU
Advisor

Re: Unable to create a LUSE in XP 24000 disk array

OK thanks for those details.
But i still have the same problem :
I wan't to create a LUSE containing 23 LDEVs;
22 of those LDEV a on a pool1 of disks (SATA disks on RAID 6 )diffirent of the 23th LDEV (FC disk on RAID 5).
i use Remote web Console to create this LUSE.
i add normally the 22 LDEV from CU 20 and CU 21.
But when i try the 23th ldev from CU 22, 24 or 26 there's no LDEV displayed.

thanks in advance

IBaltay
Honored Contributor

Re: Unable to create a LUSE in XP 24000 disk array

I wan't to create a LUSE containing 23 LDEVs;
22 of those LDEV a on a pool1 of disks (SATA disks on RAID 6 )diffirent of the 23th LDEV (FC disk on RAID 5).
i use Remote web Console to create this LUSE.
i add normally the 22 LDEV from CU 20 and CU 21.
But when i try the 23th ldev from CU 22, 24 or 26 there's no LDEV displayed.

My comments

1. it is not a good idea to create such a many members LUSE because of the performance penalty
(max is 8 or less)

2. it is not a good idea to mix SATA and FC disks, because of the huge performance difference between the

3. your problem could be that you have the 23rd LDEV with the lower CU:LDEV then the master LUSE LDEV.

Summary
your idea is very suboptimal from the point of view of the XP24k perforance and if you continuge in this direction, even the XP24K highend could start to give you the performance of the low end. You must respect the XP architecture to get the most of it....
the pain is one part of the reality
BENABBOU
Advisor

Re: Unable to create a LUSE in XP 24000 disk array

OK thanks.

I get it.

HP says the ldev in a luse must have the same RAID level.

For the perf problems i a agree with you, but the customer is aware even if this he need to create this LUSE.
Abdur Rasheedh
Occasional Visitor

Re: Unable to create a LUSE in XP 24000 disk array

It is best practice that LDEVs in LUSE must be of same RAID level, but this will not stop you from creating a LUSE with different RAID levels.