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2011 IBM Corporation Sizing Guidelines Jana Jamsek ATS Europe Slide 2 2011 IBM Corporation IBM Storage Systems IBM i performance data Good to use IBM i performance data even before modelling with Disk Magic, to apply sizing guidelines Needed reports for sizing external storage System report / Disk utilization & Storage pool utilizaton Resource report / Disk utilization Component report / Disk activity Desired way of collecting: Collect performance data during 24 hours on 3 consecutive days and during heavy End-of-month job Colleciton interval 5 minutes Insert the reports to Disk Magic to obtain data in Excell spreadsheet Slide 3 2011 IBM Corporation IBM Storage Systems Example: Spreadsheet by Disk Magic Slide 4 2011 IBM Corporation IBM Storage Systems Component report: present cache hits Slide 5 2011 IBM Corporation IBM Storage Systems Sizing the disk drives in external storage DS8800 Recommended maximal disk utilization: 60% 15K RPM SAS disk drives 10 K RPM SAS disk drives SSD DS5000 Recommended maximal disk utilization: 45% 15K RPM disk drives 10 K RPM disk drives SSD XIV Data modules Storwize V7000 Recommended maximal disk utilization: 45% 15K RPM SAS disk drives 10 K RPM SAS disk drives SSD Slide 6 2011 IBM Corporation IBM Storage Systems Guidelines for RAID level RAID-10 provides better resiliency RAID-10 provides gererally better performance: RAID-5 results in 4 disk operations per write higher penalty RAID-10 results in 2 disk operations per write lower penalty RAID-10 requires more capacity In DS8000 use RAID-10 when: There are many random writes Write cache efficiency is low Huge workload In Midrange storage and Storwize V7000 we recommend to use RAID-10 Slide 7 2011 IBM Corporation IBM Storage Systems DS8800: Number of ranks Detailed calculation for maximal IO/sec on Raid-5 rank ( reads/sec read cache hits % ) + 4 * (writes/sec write cache efficiency) = disk operations/sec (on rank) One 6+P 15 K rpm rank can handle max 2047 disk accesses/sec, at recommended 60% utilization: 1228 disk ops/sec Divide current disk accesses/sec by 1228 Example: 261 reads/sec, 1704 writes/sec, 45% read cache hits, 24 % write efficiency: (261-117) + 4 *(1704- 409) = 5324, 5324 / 1228 = 4 - 5 ranks Recommended: 4 ranks Calculation is based on performance measurements in Storage development and recommended % disk util. Slide 8 2011 IBM Corporation IBM Storage Systems DS8800: Number of ranks - continue Estimate % read cache hit and % write cache efficiency from present cache hits on internal disk Rough estimation by best practise: If % cache hits is below 50% estimate the same percentage on external storage If % cache hits is above 50% estimate half of this % on external storage If cache hits are not known or you are in doubt, use Disk Magic default estimation: 20% read cache hit, 30% write cache efficiency Slide 9 2011 IBM Corporation IBM Storage Systems DS8800: Number of ranks - continue Quick calculation based on shown detailed calcuation Example 9800 IO/sec with Read/Write ratio 50/50 need 9800 / 982 =app10 * RAID-10 ranks of 15 K rpm disk drives, connected with IOP- less adapters The table can be found in the Redbook IBM System Storage DS8000:Host Attachment and Interoperability, SG24-8887-00 Assumed cache hits: 20% read hit 30% write efficiency Slide 10 2011 IBM Corporation IBM Storage Systems DS5000/4000/3000:Number of disk drives Detailed Calculation for maximal IO/sec on disk in Raid-10 ( reads/sec read cache hits % ) + 2 * (writes/sec write cache efficiency) = disk operations/sec (on disk) Quick calculation IO/sec per DDM: 70% Read50% Read 15 K RPM disk drive RAID-1 or RAID-10 8274 RAID-55845 10 K RPM disk drive RAID-1 or RAID-10 5549 RAID-53930 Example: 7000 IO/sec with read/write ratio 70 / 30 needs 7000 / 82 =app 85 * 15 K RPM disk drives in RAID-10 Slide 11 2011 IBM Corporation IBM Storage Systems Storwize V7000: Number of disk drives Quick calculation: 70% Read50% Read 15 K RPM disk drive RAID-1 or RAID-10 138122 RAID-5 9675 10 K RPM disk drive RAID-1 or RAID-10 9282 RAID-5 6450 Example: 7000 IO/sec with read/write ratio 70 / 30 needs 7000 / 138 =app 50 * 15 K RPM disk drives in RAID-10 Slide 12 2011 IBM Corporation IBM Storage Systems Number of DDMs, connected with VIOS and SVC The sizing guidelines and calculations for DDMs in Storage systems connected with VIOS or VIOS_NPIV dont change The sizing guidelines and calculations for DDMs in Storage systems connected with SVC and VIOS dont change Slide 13 2011 IBM Corporation IBM Storage Systems Sizing for big blocksizes (transfer sizes) Big blocksize: 64 KB and above Add about 25% disk arms for big blocksizes The shown guidelines assume small blocksize (about 12 KB) Peak in IO usually experiences small blocksizes Peak in blocksizes has typically low IO/sec So usually we size for peak in IO/sec and dont update with additional 25% Slide 14 2011 IBM Corporation IBM Storage Systems Number and size of LUNs With given disk capacity: The bigger the number of LUNs the smaller the size Sizing guidelines for the number, or for the size To obtain the number of LUNs you may use WLE ( number of disk drives) Considerations for very big number of LUNs: Many physical adapters are needed for natively connected storage Difficult to manage and troubleshoot with big number of virtual adapters in VIOS Slide 15 2011 IBM Corporation IBM Storage Systems DS8000 Guideline by best practise: 2 * size of LUN = 1 * size of DDM, or 4 * size of LUN = 1 * size of DDM Presently 70 GB or 140 GB LUNs are mostly used DS5000 Guideline: Big LUNs enable better seek time on disk drives Small LUNs big number of LUNs enable more concurrent IO to disk space Compromise: 70 GB or 140 GB LUNs DS5000 best practise: 146 GB physical disks Make RAID-1 arrays of tow physical disks and create one logical drive per RAID-1 array. Recommended segment size 128 KB or 64 KB Create one LUN per array If the number of LUNs is limited to 16 (for example, connecting to IBM i on BladeCenter) you may want to make a RAID-10 array of four physical disks and create one LUN per array. Number and size of LUNs -continue Slide 16 2011 IBM Corporation IBM Storage Systems Number and size of LUNs -continue XIV - best pracise for the size of LUNs: Measurements in Mainz: CPW 96000 users, 2 concurrent runs in different LPARs 15-module XIV Gen 3 Transaction resp. Time (sec) Disk service time (ms) Latency in XIV% Cache hits in XIV 42 * 154 GB LUNs 6.64.6480 6 * 1TB LUNs19.38.2760 70 GB LUNs were not tested Recommendation: about 140GB LUNs, or 70GB LUNs Slide 17 2011 IBM Corporation IBM Storage Systems Number and size of LUNs -continue Storwize V7000, SVC Presently we recommend about 140 GB LUNs This recommendation is based on best practise by other midrance storage systems Recommended to craete vdisks in Striped mode ( default ) Recommended extent size 256 MB ( default ) Slide 18 2011 IBM Corporation IBM Storage Systems Guidelines for different types of connection The listed guidelines for a particular storage system apply to all cases (when applicable): Native connection Sizing for physical FC adapters applies to natively connected storage Connectioned with VIOS vscsi Connection with VIOS_NPIV Connection via SVC The size of LUNs applies to SVC vdisks Slide 19 2011 IBM Corporation IBM Storage Systems Sizing FC adapters in IBM i by IO/sec #5774 or #5749#5735 IO/sec at 70% utilization 10500 per port12250 per port GB per port in adapter 28003266 Example: for one port in #5735 we roecmmend 3266 / 70 = 46 * 70 GB LUNs Example: For 2 ports in Multipath we recommend 2 * 46 = 92 -> 64 * 70 GB LUNs in Multipath Assumed: Access Density = 1.5, For 2 path: multiply the capacity by 2 Slide 20 2011 IBM Corporation IBM Storage Systems Throughput of IOP-less adapters #5774 or #5749#5735 Max sequential throughput 310 MB/sec per port400 MB/sec Avg of max sequential throughput for 4KB, 256KB raeds, writes 216 MB/sec per port Avg of min sequential throughput for 4KB, 256KB raeds, writes 132 MB/sec per port Max transaction workload throughput 250 MB/sec per port Transaction workload throughput at 70% utilization 175 MB/sec per port Avg of max sequential throughput for 4KB, 256KB raeds, writes 382 MB/sec per 2 ports Avg of min sequential throughput for 4KB, 256KB raeds, writes 208 MB/sec per 2 ports Slide 21 2011 IBM Corporation IBM Storage Systems Adapters on HSL loops Slide 22 2011 IBM Corporation IBM Storage Systems Sharing or dedicating ranks Sharing ranks among multiple IBM i LPARs Enables better usage of resources in external storage On the other hand the performance of an LPAR might be influenced by workloads in other LPARs Dedicating ranks to each LPAR Enables stable performance (no influence from other systems) Resources are not as well utilized as with shared ranks Best practise: Dedicate ranks to big and/or important systems Share ranks among medium and small LPARs Slide 23 2011 IBM Corporation IBM Storage Systems Guidelines for cache size in external storage Modelling with Disk Magic Rough guidelines for DS8800 10 to 20 TB capacity: 64GB cache 20 to 50 TB: 128 GB cache > 50 TB: 256 GB cache Slide 24 2011 IBM Corporation IBM Storage Systems Number of HA cards in DS8800 Rules of thumb for HAs in DS8800 About 4 to 8 * ports in IBM i per one HA card in DS8800 For high performance: The number of HA cards should be the same or bigger than the number of device adapters in DS8800 At least one HA card per IO enclosure in DS8800 Slide 25 2011 IBM Corporation IBM Storage Systems Sizing for VIOS Slide 26 2011 IBM Corporation IBM Storage Systems Sizing IASP Very rough guideline: about 80% of IO will be done to IASP System report Resource utilization; IO to database Slide 27 2011 IBM Corporation IBM Storage Systems Sizing for SSD Slide 28 2011 IBM Corporation IBM Storage Systems Sizing for Metro Mirror or Global Mirror links