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1 TB RAID 1 LUN -VNX 5800
Hi,
I am going to assign a LUN of 1 TB disk space (4x 600 GB15k SAS disks available ) , this LUN should be on RAID 1 configuration and not applicable to the FAST-VP (auto-tier) ,,what is the best way to create a LUN of that size??
Should i create a separate pool contains the four SAS disks with RAID 1 ( but there is no option to choose RAID 1 in the pool creation)
or should i create a RAID group then a traditional LUN from this group ( but how to get 1 TB from 4 disks in a RAID 1 group)
Your help is greatly appreciated.
Regards,
Ahmad
brettesinclair
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715 Posts
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May 19th, 2015 15:00
You cannot create a RAID 1 pool/group from 4 disks. You will have to create 2 x 2 disk elements and then either concat or construct them at an os level.
Why is your DBA so adamantly opposed to any striping, does he/she even understand it or just reading from a potentially outdated Oracle BP document ? Is it currently best practice to avoid redo logs on R1/0 ? A quick check only turned up an old doc.
I'm not convinced all the effort and configuration you are proposing is justified, but I'm certainly not an oracle expert so happy to defer to anyone who is. You might consider getting some opinions from the experts here Everything Oracle at EMC
brettesinclair
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May 18th, 2015 05:00
No, RAID1/0 is the choice, which obviously is mirrored and striped.
I don't know why RAID 1 is not available, perhaps as it's not easy to expand, whereas 1/0 is.
May I ask why you are trying to avoid any striping ?
brettesinclair
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715 Posts
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May 18th, 2015 05:00
Hi, There's been a lot of debate over the years around Pools versus RAID Groups.
In my opinion, just use Pools, and keep it consistent. The performance difference is effectively nothing. Recent study here:
Virtualized Storage Performance: RAID Groups versus Storage pools | VMware VROOM! Blog - VMware Blogs
You'll probably need to change the disk selection to manual to create a pool of 4 disks in RAID 1/0. Keep in mind the best practice is 4+4, so if you ever need to expand it, try to do so with another group of 4 disks so the private RAID Groups remain consistent.
Ahmadgmc
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May 18th, 2015 05:00
Thank you Brett.
RAID 1/0 : does it mean RAID 10 or RAID 1 or RAID 0 and i have to select one of them .
I have to avoid any type of stripping so RAID is not an option for me. i just need a RAID 1 LUN.
does the VNX support such configuration ? creating new pool and choose 4 SAS disks and select RAID 1 on the 4 disks to get 1 TB ???
appreciated.
Ahmadgmc
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May 18th, 2015 06:00
what about RAID 1 RG ??? Can i create it from 4 disks ??? and get the 50 % of capacity ???
Roobeek
12 Posts
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May 18th, 2015 06:00
You should create a raid10 raidgroup. within that raidgroup you can create a 1 TB lun. This will also give you the advantage of an active/active lun.
Ahmadgmc
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May 18th, 2015 06:00
thanks, so 1/0 means RAID 10 (stripe of mirrors) and it requires minimum 4 disks however here that data will be stripped and this does not meet the application requirements.
it's an oracle database with archive log files, Oracle recommends ( as far as i know and after checking this with oracle) that the archive log files should be stored in non-stripping LUN (RAID 1 volume).
the DBA was requesting this LUN with its characteristics.
I can not find RAID 1 under pool creation wizard?? should i create a TLUN ??
Roobeek
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May 18th, 2015 06:00
by the way, raid 1/0 gives the same charesteristics as raid 1 so it will meet the requirements. It has the same write penalty. and same performance hit when there is a disk failure.
Roobeek
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May 18th, 2015 06:00
You can create a 4 disk raid 1/0raidgroup. This will give you about 1066 GB of usable capacity (one 600GB disk = 533 GB usable). you cannot create a raid 1 raid group (EMC only gives you an option for raid 1/0). If you only want to use 2 disks in a mirror it has to be a raid 1/0 with 2 disks.
Ahmadgmc
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May 19th, 2015 08:00
I agree with you that RAID 10 has the same characteristics of RAID 1 in addition to the stripping, but what we need is a RAID 1 LUN ( we have to avoid any type of stripping )
Rainer_EMC
8.6K Posts
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May 19th, 2015 09:00
Then why not create two 2-disk R10 and concat them ?
Ahmadgmc
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May 19th, 2015 11:00
actually what I am trying to figure out if there is a way to create RAID 1 LUN from 4 disks ( either using storage pool or TLUN) ,
I can create two RAID 1 RG, each one consists of two disks then create two LUNs from each RG and present them to the host.
at the host level i will use LVM to create one logical volumes from the two LUNS
is it a complicated way to configure what we need ?? frankly i don't like concatenation of two LUNS at the storage level.
Thanks.