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EMC CX3-40 enclosure adition and Raid group creation
Hi All,
We have a EMC CX3-40 storage .We are planning add an additional disk enclosure . It has 15 x 300 GB 15 K RPM FC drives . I am planning to do below mentioned steps .
1. Install the DAE and drives using NST .
2. Create 3 raid groups , 1-5 drives in 1st Raid Group, 6-10 2nd Raid group, 11-14 3rd Raid group and 15th disk hot spare . I am planning for Raid 5 for these raid groups .
IS it a good configuration ?. We cannot create spanned raid groups ( spanned across multiple enclosures , since they are already used and cannot even touchhhhhh ...... )
Am planning to create 3 luns in each above mentioned raid groups having 150 GB each and going to merge to make a meta with stripe . As i mentioned 3 rd raid group is having 4 drives and other two raid groups are having 5 each . Can i create meta using stripe ?.
One hot spare is ok for this ?
Thanks in advance ....
Vinod
We have a EMC CX3-40 storage .We are planning add an additional disk enclosure . It has 15 x 300 GB 15 K RPM FC drives . I am planning to do below mentioned steps .
1. Install the DAE and drives using NST .
2. Create 3 raid groups , 1-5 drives in 1st Raid Group, 6-10 2nd Raid group, 11-14 3rd Raid group and 15th disk hot spare . I am planning for Raid 5 for these raid groups .
IS it a good configuration ?. We cannot create spanned raid groups ( spanned across multiple enclosures , since they are already used and cannot even touchhhhhh ...... )
Am planning to create 3 luns in each above mentioned raid groups having 150 GB each and going to merge to make a meta with stripe . As i mentioned 3 rd raid group is having 4 drives and other two raid groups are having 5 each . Can i create meta using stripe ?.
One hot spare is ok for this ?
Thanks in advance ....
Vinod
ASR2
32 Posts
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October 2nd, 2008 06:00
When talking about the layout of drives in the DAE start with drive 0
so your first RG will be on drives 0,1,2,3,4 , 2nd RG on 5,6,7,8,9 , 3rd on 10,11,12,13 with hotspare drive 14
IS it a good configuration ? It depends on what applications you are going to put onto the luns , if the IO profile is suited to Raid 5 then yes thats a good configuration
Can i create meta using stripe ? Yes ,
Are you going to stripe the meta across all three raidgroups ?
When binding component LUNs, follow these rules:
¿ Always use the default stripe element size (128 blocks) when binding LUNs for use in metaLUNs.
¿ Always activate read and write cache.
¿ Avoid using LUNs from RAID 5 groups of fewer than four drives (in other words, use 3+1 or larger).
¿ Do not use the component LUN offset to adjust for stripe alignment. MetaLUNs have their own offset value.
Mosa3lyan
265 Posts
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October 2nd, 2008 09:00
nandas
1.5K Posts
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October 2nd, 2008 09:00
Happy posting
Cheers,
Sandip
nandas
1.5K Posts
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October 2nd, 2008 09:00
ASR had provided the detailed answers and tips to almost all your questions. However, I like to add few things here -
1) You may consider creating 4 LUNs on each RAID group and then creating the Metas - this will balance the SPs - if you create 3 LUNs - you have to choose 2 sets on one SP and one set of the other SP. This may not be a problem at all - and of course we don't have the details of your existing configuration - how the SPs are balanced. But may be something you may look at
2) You can definitely create striped Meta LUN using all 3 RAID groups - but since the last RAID group has lesser capacity (4 drives) - you will not be able to use the first 2 RAID Groups to their capacity for creating Metas. You may leave the space free for future use - or create individual LUNs or create another Meta on the first two RAID groups only.
3) If you already have existing Hot Spare for 300 GB FC disks - you may consider not configuring any Hot spare for the new enclosure - rather create 3 RAID 5 groups each having 5 disks (even configuration) - which will eliminate the issue of one Raid Group having lesser capacity.
4) In this context - we are assuming you have proper understanding of your requirement and feel that RAID 5 may be a good fit. However, if you need any RAID 1 or RAID1/0 - you may consider creating a RAID1/0 group using the 4 drives. In that case, you are left with 2 RAID groups of RAID 5 and the Metas need to be created on these two RAID groups. Again - it depends on your requirement.
5) One hot spare is more than OK for this enclosure - but as I mentioned earlier - you may consider not keeping any hot spare on this enclosure if you have other 300 GB Hot spare. Typical thumb rule is to keep one hot spare for every 30 disks.
My 2 cents (or little bit more than 2 cents
Cheers,
Sandip
vinukkuttan
5 Posts
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October 5th, 2008 18:00
Vinod