Hello I recently had a discussion about this with one of our consultants. Currently, we have 405 disks in our CX3-80 (27 DAE's, all filled with 300 GB FC disks) He claimed that it wouldn't be advisable to put the maximum amount of disks in our array. He thought that this would have a negative impact on the performance. I don't see how this could be the case, considering that we are way below all the other limits, that according to me have more impact on performance:
- Default, we use RAID5 8+1 raid groups, so with 480 disks, after subtracting disks reserved for hot spare, that would give around 51 raid groups (max: 240) - We currently have 31 hosts connected, each with 6 paths, so in total 186 host initiators (max: 512) - 93 LUNs, with an average size somewhere between 256-512 GB each. If we maintain this size of LUN, it should keep us far beyond the max limit of 2048 LUNs - 41 MirrorView/S relationships (max: 200) - and at the moment, I don't see any problems with the actual load that each host generates
So, under these circumstances, do you think that we can safely put the maximum number of disks in our clariion?
With these informations I only see the performance aspect which could be the reason not to add more disks.
I have asked to EMC to take a look at our configuration to know if I can add a server which needs big performances and which stores big data. The result was "yes we can" and the main things to see were : - SPs utilization - SPs throughput - % dirty pages - forced flushes / s
When you add disks you don't add SP and cache, so you have to be careful you have sufficient resources.
That is a good point to bring up. I have 465 disks on my Cx3-80 right now and that amount of disks has definitely decreased the overall performance of the array. Time to upgrade to a Cx4-960
Or sometimes it is even better to buy another CX than adding disks in an old one. Let's say you keep your CX3-80 and buy a little CX4 ? But what a pitty not to have the huge brand new CX4-960 !
nandas
1.5K Posts
0
November 25th, 2008 10:00
Thanks,
Sandip
nandas
1.5K Posts
0
November 24th, 2008 14:00
Hope this is what you were looking for.
Thanks,
Sandip
jcoenen1
5 Posts
0
November 26th, 2008 00:00
I recently had a discussion about this with one of our consultants.
Currently, we have 405 disks in our CX3-80 (27 DAE's, all filled with 300 GB FC disks)
He claimed that it wouldn't be advisable to put the maximum amount of disks in our array. He thought that this would have a negative impact on the performance. I don't see how this could be the case, considering that we are way below all the other limits, that according to me have more impact on performance:
- Default, we use RAID5 8+1 raid groups, so with 480 disks, after subtracting disks reserved for hot spare, that would give around 51 raid groups (max: 240)
- We currently have 31 hosts connected, each with 6 paths, so in total 186 host initiators (max: 512)
- 93 LUNs, with an average size somewhere between 256-512 GB each. If we maintain this size of LUN, it should keep us far beyond the max limit of 2048 LUNs
- 41 MirrorView/S relationships (max: 200)
- and at the moment, I don't see any problems with the actual load that each host generates
So, under these circumstances, do you think that we can safely put the maximum number of disks in our clariion?
Regards,
Johan
ovivier
142 Posts
0
November 26th, 2008 00:00
CX3-80 = 4 buses
1 bus = 8 DAE max
1 DAE = 15 disks max
4*15*8 = 480 disks
ovivier
142 Posts
0
November 26th, 2008 05:00
With these informations I only see the performance aspect which could be the reason not to add more disks.
I have asked to EMC to take a look at our configuration to know if I can add a server which needs big performances and which stores big data. The result was "yes we can" and the main things to see were :
- SPs utilization
- SPs throughput
- % dirty pages
- forced flushes / s
When you add disks you don't add SP and cache, so you have to be careful you have sufficient resources.
AranH1
2.2K Posts
0
November 26th, 2008 08:00
ovivier
142 Posts
0
November 27th, 2008 04:00
Let's say you keep your CX3-80 and buy a little CX4 ? But what a pitty not to have the huge brand new CX4-960 !