This post is more than 5 years old
10 Posts
1
1002
November 5th, 2013 11:00
FAST and Bound to pool
I have created 10 devices and bound to FC pool with FAST policy 100-100-100, What difference does it make if I bound to SATA pool and associate same FAST policy of 100-100-100??
No Events found!
PedalHarder
3 Apprentice
•
465 Posts
0
November 17th, 2013 15:00
A RAID 6 write is 3 read and 3 write disk operations. A SATA disk can do around 50 IOPS. You can multiply out the number of disks and host writes (plus reads) to work out how capable your SATA tier is.
For RAID 1, it is 2 disk writes per write and for RAID 5, its 2 reads and 2 writes per host write.
An FC 10K is capable of around 120 IOPS and a 15K around 150 IOPS.
It's just a case of taking the IOPS rating of the disk, applying the RAID overhead to the read / write ratio and host IOPS to see how busy your tier will be from a host IOPS perspective.
e.g. Your host is bound to (RAID 6) SATA and does 120 writes and 50 read miss per second.
120*6+50=770.
770(disk IOPS) / 50(SATA rating) = 16 SATA disks required to support the workload.
Compare this to a RAID 1 FC pool:
120*2+50=290.
290/120=2.5
You need way less FC disk from a performance perspective in this example and supports the earlier comments that the FC tier is typically best practice as the tier for the initial bind. You should be able to use the above to make an infiormed decision on where do bind your devices to.
Don't forget there can be other overheads on the disk:
- FAST movement
- Local replication
- Drive failures
christopher_ime
2K Posts
0
November 5th, 2013 21:00
Please consider moving this question as-is (no need to recreate) to the proper forum for maximum visibility. Questions written to the users' own "Discussions" space don't get the same amount of attention and can go unanswered for a long time.
You can do so by selecting "Move" under ACTIONS along the upper-right. Then search for and select: "Symmetrix Support Forum".
Symmetrix Support Forum
SYMCLIGuy
98 Posts
0
November 6th, 2013 08:00
By default, new allocations resulting from host writes to a thin device will come from the pool the device is bound to. If you bind the devices to SATA, all new allocations will come from the SATA pool. This is not recommended as you will want to avoid a large number of writes happening on SATA as it is typically going to be configured as RAID 6.
In 5876 code, a new feature called VP allocation by FAST policy was introduced which allows new allocations to come from any of the pools in the policy the device is associated with. Most allocations, however, will still likely come from the pool the device is bound to.
The best practice receommendation is to bind all thin devices to the FC tier.
Take a look at the FAST VP best practices guide located at
https://support.emc.com/docu31003_FAST_VP_for_Symmetrix_VMAX_Theory_and_Best_Practices_for_Planning_and_Performance.pdf?language=en_US
It contains a full description of the allocation by policy feature. It also contains the best practices recommendation on where devices should be bound (and why).
Zhang_Jiawen
2 Intern
•
1.2K Posts
0
November 12th, 2013 19:00
SATA device are for large data and without any performance concerns.(best practise should be RAID 6).
Fast VP will not make SATA drives any faster. If you put too many unimportant workloads on the SATA tier, it can impact the whole system. So, workloads pinned to SATA pool need to be sized appropriately, and the workload on the SATA tier can impact all tiers in the same system.
The best-practice recommendation is to bind all thin devices to a pool within the FC tier.
VP allocation by FAST policy should be enabled.
It is not recommended to bind thin devices, under FAST VP control, to the EFD tier.
A best-practice recommendation is to not pre-allocate thin devices managed by FAST VP.
dynamox
9 Legend
•
20.4K Posts
0
November 12th, 2013 20:00
while best practices are always good to follow there are business decisions why some could be omitted, for example full thin device per-allocation.
Fenglin1
4 Operator
•
2.1K Posts
0
November 12th, 2013 20:00
It depends on your frontend APPs, if your APPs are write sensitive, it's nor recommended to bound SATA during initially configuration unless FAST VP will move data from SATA to EFD. But you have lower performance of data on SATA tier from the beginning of allocation.
sanman999
10 Posts
0
November 17th, 2013 06:00
But I am looking from Read/write iops persepective.....
What difference does it make, ie, how is write is written and reads are done in both Scenarios.....