 The following table lists and defines metrics for Symmetrix  devices.  % hit 100 * (total hits per sec / total ios per  sec) Percentage of I/O operations, performed by the  Symmetrix device, that were immediately satisfied by cache. % miss 100 - (% hit) Percentage of read and write miss operations  performed each second by the Symmetrix device that were misses. A miss occurs when the requested read data is not  found in cache or the write operation had to wait while data was destaged from  cache to the disks. % random read  hit 100 * (read hits per sec / total ios per  sec) % random  read miss 100 * (read misses per sec / total ios per  sec) % read 100 * (total reads per sec / total ios per  sec) Percentage of read I/O operations performed by  the Symmetrix device. % read hit 100 * (total read hits per sec / total reads per  sec) Percentage of read hit I/O operations performed  each second by the Symmetrix device. Read hits occur when the read operation is  satisfied directly from cache. % read  miss 100 * (total read misses per sec / total reads  per sec) Percentage of read miss I/O operations performed  by the Symmetrix device. Read misses occur when the data requested by the  read I/O operation was not in cache, causing a wait while it was fetched from  disk. % sequential  io 100 * (seq ios per sec / total ios per sec) Use this metric for mainframe performance analysis  only. % Sequential  read 100 * (seq reads per sec / total ios per sec) Use this metric for mainframe performance analysis  only. %  sequential writes 100 * (seq writes per sec / total ios per  sec) Use this metric for mainframe performance analysis  only. % write 100 * (writes per sec / total ios per sec) Percentage of total write I/O operations  performed each second by the Symmetrix device. % write  hits 100 * (write hits per sec / writes per sec) Percentage of write hit I/O operations performed  by the Symmetrix device. A write hit occurs when the I/O write operation is  received, it is immediately staged in cache and will be written to disk at a  later time. % write  miss 100 * (write misses per sec / writes per sec) Percentage of write I/O operations performed each  second by the Symmetrix device that were write misses. A write miss occurs when  the I/O write operations are delayed because the system or device write-pending  limit was reached and the cache had to destage slots to the disks before the  writes could be written to cache. average io size  in Kbytes (HA Kbytes transferred per sec) / (total ios per  sec) Average size of an I/O operation performed by the  Symmetrix device. average read  size in Kbytes (Kbytes read per sec) / total reads per sec) Average size of a read I/O operation performed by  the Symmetrix device. average write size in  Kbytes (Kbytes written per sec) / (writes per  sec) DA Kbytes read per  sec Number of kilobytes read by the disk directors  from the disk each second. DA Kbytes  transferred per sec (DA Kbytes read per sec) + (DA Kbytes written per  sec) Sum of the kilobytes read and written each second  on all disk directors associated with the Symmetrix device. DA Kbytes written  per sec Number of kilobytes written to the disk from the  disk director each second. DA prefetched  tracks per sec Total prefetched tracks each second from the disk  directors to the cache. DA  prefetched tracks Used per sec Number of prefetched tracks used each second from  the disk directors to the cache. DA read requests  per sec Number of read requests each second performed by  the disk directors to the cache. DA write requests  per sec Number of write requests each second performed by  the disk directors to the cache. HA Kbytes  transferred per sec (Kbytes read per sec) + (Kbytes written per  sec) Total number of kilobytes read and written each  second through host directors associated with the Symmetrix  device. hits per  sec Number of I/O operations performed each second by  the Symmetrix device that were immediately satisfied by cache. ios per  sec Number of I/O operations performed each second by  the Symmetrix device, including writes and random reads. In contrast, the total ios per secmetric includes writes, random reads, and sequential reads. Kbytes read  per sec Number of kilobytes read by the Symmetrix device  each second. Kbytes  written per sec Number of kilobytes written by the Symmetrix  device each second. max write  pending Threshold Maximum number of write-pending slots available for the  Symmetrix device. Max Write Pending Threshold is not a static  number. It depends on Symmetrix activity. Each Symmetrix device is assigned a  limit of write-pending slots that can dynamically change between a base value  and a value three times the base (the maximum value). Once the Max Write Pending  Threshold has reached three times the base value, writes to the device are  delayed so that the cache can destage, which frees the cache slots. As cache  slots are freed, the writes resume. While the write-pending limit is reached,  disk directors operate in a priority destage write mode. This gives write data  higher priority than usual. During the delay, writes to this Symmetrix device  are counted as write misses. Note: If you have a newer DMX, such as a  DMX3 or DMX4,  the device limit is 5% of the system write pending  limit. read hits per  sec Number of random read hit I/O operations  performed each second by the Symmetrix device. Read hits occur when the read I/O  operation is satisfied directly from cache. The read hits per sec metric for the  Symmetrix device statistic does not include sequential read hits. In contrast,  the metric total read hits per secincludes random and sequential read hits per sec. read misses  per sec (reads per sec) - (read hits per sec) Read misses occur when the data requested by the  read I/O operation was not in cache, causing a wait while it was fetched from  disk. random reads per  sec Number of I/O operations performed each second by  the Symmetrix device that were random reads. This Random Reads per sec metric  for the Symmetrix device statistic does not include sequential reads. In  contrast, the metric total read hits per secincludes random and sequential read hits per sec. sampled average  reads missed time (ms) Completion time of a read-miss as measured by the  host director. Measurements are taken for a sample set of approximately 30% of  the I/Os. Read misses occur when the data requested by the  read I/O operation was not in cache, causing a wait while it was fetched from  disk. Metadevices: This is approximately (within  milliseconds) the same response time that the host sees at the head of the meta.  The value is calculated by dividing the total sampled elapsed time by the number  of sampled events. The number of sampled events counter, and sampled elapsed  time counter are maintained for all metamembers under the statistics for the  head of the meta. sampled average read  time (ms) Completion time of a read as measured by the host  director. Measurements are taken for a sample set of approximately 30% of the  I/Os. Metadevices: This is approximately (within  milliseconds) the same response time that the host sees at the head of the meta.  The value is calculated by dividing the total sampled elapsed time by the number  of sampled events. The number of sampled events counter, and sampled elapsed  time counter are maintained for all metamembers under the statistics for the  head of the meta. sampled average write  time (ms) Completion time of a write as measured by the  host director. Measurements are taken for a sample set of approximately 30% of  the I/Os. metadevices: This is approximately (within  milliseconds) the same response time that the host sees at the head of the meta.  The value is calculated by dividing the total sampled elapsed time by the number  of sampled events. The number of sampled events counter, and sampled elapsed  time counter are maintained for all metamembers under the statistics for the  head of the meta. sampled average  WP disconnect time (ms) Completion time of a write-miss as measured by  the host director. Measurements are taken for a sample set of approximately 30%  of the I/Os. A write miss occurs when a write I/O is held  while data is destaged from cache. Metadevices: This is  approximately (within milliseconds) the same response time that the host sees at  the head of the meta. The value is calculated by dividing the total sampled  elapsed time by the number of sampled events. The number of sampled events  counter, and sampled elapsed time counter are maintained for all Metamembers  under the statistics for the head of the meta. sampled RDF writes waits per second Number of I/O operations performed while waiting  for an RDF transfer. This is simply a counter. seq ios per  sec (seq reads per sec) + (seq writes per sec) Use this metric for mainframe performance  analysis only. seq read  hits per sec Portion of the explicitly counted sequential  reads that were satisfied from the cache on request. Information about the type of environment you are  working in. Mainframe environment: The  Sequential read hits per sec is useful as a sequential counter. Open System environment: The  SCSI I/O command does not have indicators to identify whether the I/O is part of  a sequential stream, so the counts are not actual indicators of full sequential  activity. This metric is needed  for open systems to calculate the metric total reads per sec. This metric must be added to the read hits per sec to get the value for the  Total read hits per sec. seq reads per  sec Information about the type of environment you are  working in. Mainframe environment: The seq  reads per sec is useful as a sequential counter. Open System environment: The  SCSI I/O command does not have indicators to identify whether the I/O is part of  a sequential stream, so the counts are not actual indicators of full sequential  activity. In an open-system  environment the Sequential Read metric indicates to the back end to start  pre-fetch activity after two sequential read misses occurred in a row. In the case where the data is in cache and all  reads are hits, the back end does not get involved and therefore there is no  indication that the read is sequential. This metric is still needed for open systems to  calculate the total reads per sec metric. Since sequential read misses are not  included in the read counters the seq reads per sec must be added to the Random  Reads per sec to get the value for the Total Reads per sec. seq writes  per sec Number of write I/O operations performed each  second that were sequential. Use this metric for mainframe performance analysis  only. system bus Kbytes per  sec (HA Kbytes transferred per sec) + (DA Kbytes  transferred per sec) total DA req per sec (DA read requests per sec) + (DA write requests  per sec) total hits  per sec (total read hits per sec) + (write hits per  sec) Total number of I/O operations performed each  second by the Symmetrix device that were immediately satisfied by  cache. total ios per  sec (total reads per sec) + (writes per sec) Total number of read I/O and write I/O operations  performed each second by the Symmetrix device. total  misses per sec (total ios per sec) - (total hits per sec) Total number of missed I/O operations performed  each second by the Symmetrix device. total  read hits per sec (read hits per sec) + (seq read hits per sec) Total number of read hits and sequential read hit  operations performed each second by the Symmetrix device. total reads  per sec (random reads per sec) + (seq reads per sec) Total number of random read and sequential read  operations performed each second by the Symmetrix device. write hits  per sec Number of write hit operations performed each  second by the Symmetrix device. A write hit occurs when the I/O write operation  is received, it is immediately staged in cache and will be written to disk at a  later time. write  misses per sec (writes per sec) - (write hits per sec) This number of write misses that occurred for the  Symmetrix device each second. A write miss occurs when the I/O write operations  are delayed. write  pending count Number of cache slots that were write pending for  the logical volume at a point in time. This number changes according to the  cache destage activity rate and the number of writes. A write is pending when it  has been written to cache but has not yet been written to the  disk. writes per  sec Number of write I/O operations performed each  second by the Symmetrix device.    Symmetrix disk metrics The following table lists and defines metrics for Symmetrix  disks.  % busy 100 - %disk idle % idle Disk Idle Time Per Sec * 100 %  utilization This metric shows how close the disk performance  is to 100% utilization. Percentage is based on the number of SCSI  commands being performed by the disk. accumulated queue depth Sum of queue depths for the disk when an event  enters this range (0 - over 640). average hypers per  seek (seek distance per sec) / (seeks per sec) Average number of hypervolumes that the disk head  crossed during one seek. average Kbytes per  read (Kbytes read per sec) / (read commands per  sec) average Kbytes per  write (Kbytes written per sec) / (write commands per  sec) average busy queue  depth Average Queue Depth / (1 - Disk Idle Time Per  Sec) Ratio of Average Queue Depth to the time the disk  is busy. average  queue depth Calculated against the Accumulated Queue Depth  and Total SCSI Commands Per Sec. average  read time (total read time per sec) / (read commands per  sec) average  write time (total write time per sec) / (write commands per  sec) disk  idle time per sec Average time per second that the disk is  idle. Kbytes  read per sec Number of kilobytes read by the Symmetrix disk  each second. Kbytes  written per sec Number of kilobytes written by the Symmetrix disk  each second. read  commands per sec Number of read operations performed each second  by the Symmetrix disk. seek  distance per sec Number of hypervolumes that the disk head crossed  (during all seeks) each second. seeks per  sec Number of times each second that the disk head  moved to find data. skip mask commands per  sec Number of skip mask commands performed each  second by the disk. Skip Mask enables a fragmented track, which is  chunks of data with gaps in between, to be read from disk or written to disk in  one I/O operation. Without Skip Mask, each chunk of data is read or written in a  separate I/O operation, causing a fragmented track to require multiple I/O  operations to read or write. total SCSI commands per  sec Total number of read commands, write commands,  skip mask commands, verify commands, XOR write commands, and XOR write-read  commands performed by the Symmetrix disk each second. verify  commands per sec Number of verify commands performed each second  by the disk. Verify commands are background scrubbing  operations performed periodically to check data integrity on the  drives. write  commands per sec Number of write operations performed each second  by the Symmetrix disk. XOR write commands per  sec Number of exclusive OR (XOR) write commands  performed each second by the disk. XOR commands are used to establish parity  protection in RAID-S and RAID 5 configurations. In a RAID-S or RAID 5 environment, 3 physical  I/Os for each write operation are generated: write, XOR-write-read, and  XOR-write. When a write is issued to a disk, which is a member of a RAID-S or  RAID 5 set, the write is immediately followed by an XOR-write-read command. The  XOR-write-read command extracts the necessary information for parity protection.  The information is then written to the parity disk using the XOR-write  command. XOR write-read commands per  sec Number of exclusive OR (XOR) write-read commands  performed each second by the disk. XOR commands are used to establish parity  protection in RAID-S and RAID 5 configurations. In a RAID-S or RAID 5 environment, 3 physical  I/Os for each write operation are generated: write, XOR-write-read, and  XOR-write. When a write is issued to a disk, which is a member of a RAID-S or  RAID 5 set, the write is immediately followed by an XOR-write-read command. The  XOR-write-read command extracts the necessary information for parity protection.  The information is then written to the parity disk using the XOR-write  command. Symmetrix disk director metrics The following table lists and defines metrics for disk  (back-end, or dadir) directors. % read 100 * (reads per sec / requests per sec) Percentage of read requests performed by the disk  director. % seq reads 100 * (prefetched tracks per sec / (prefetched  tracks per sec + reads per sec)) Percentage of read requests that were sequential.  A sequential read occurs when the tracks brought into cache by prefetch tasks  are read in the order in which they were put in cache. %  utilization This metric shows how close the disk director  (back-end director) is to 100% performance utilization. Percentage is based on the number of I/O  operations being performed by the disk director. % write 100 * (writes per sec / requests per sec) Percentage of write requests performed each  second by the disk director. accumulated director  idle time Number of ticks that elapsed while the director  did not have any requests in its queue. average lru0 fall  through time Average time it takes a cache slot in LRU0 to be  freed up. It is the average time from the first use of the contents to its reuse  by another address. This is a key metric that Symmetrix algorithms  use to manage the cache. It is a measure, on average, in seconds, of how long it  takes a slot to go from the top of the LRU to the bottom of the LRU for  reselection. The time only measures from the last time the slot is placed at the top of the LRU to the time  it reaches the bottom of the LRU. Each time a slot is placed at the top of the  LRU, the time value used to calculate the Fall Through Time is reset to current  time (effectively, zero). Average is calculated using between 4000 - 8000  slots. This metric is a sometimes misunderstood  Symmetrix statistic. The cache algorithms may have placed the slot at the top of  the LRU many times before the slot finally reaches the bottom of the LRU. The  total time the slot is in the cache would have to account for all of the times  the slot was placed at the top of the LRU. This would equal cache residency time  (time of reselection minus the time of entry). A common mistake is to think that  Fall Through Time is cache residency time. Cache residency time does not exist  in Symmetrix statistics. ios per  sec Number of I/O operations performed each second  between the Symmetrix disk director and the disk. long misses per sec Number of times each second that requested data  was not in cache, and was not in the process of being fetched. queue  depth count Number of events that are waiting while the  director's queue is in this range (0 - over 640). permacache  requests per sec Number of requests between permacache and the  disk director each second. Permacache is the part of cache reserved for a  particular application. A request is the protocol used by directors (host and  disk) to marshal data to and from the cache. prefetched tracks per sec Number of tracks prefetched to cache each second  by the disk director. reads per  sec Number of read requests performed each second by  the Symmetrix disk director. requests per  sec Number of request operations performed by the  disk director. A request is the protocol used by directors (host  and disk) to marshal data to and from the cache. This metric is made up of reads  and writes. short  misses per sec Number of times each second that requested data  was not in cache, but was being fetched when the request was  executed. tracks not used  per sec Number of prefetched tracks per sec that have not  been used to satisfy a read request. For more information, see prefetched tracks per sec. tracks used  per sec Number of prefetched tracks per sec that were  used to satisfy read requests. For more information, see prefetched tracks per sec. writes per  sec Number of write requests performed each second by  the Symmetrix disk director.  Symmetrix host director metrics The following table lists and defines  metrics for ESCON, fibre, Ficon, and SCSI host (front-end, or sadir)  directors.  % busy 100 - %idle This metric is available only for Fibre Channel  directors. % hit 100 * (hits per sec / requests per sec) Percentage of requests performed by the host  director and immediately satisfied by cache. % idle Ratio of Accumulated Director Idle Time to  interval time. This metric is available only for Fibre Channel  directors. % read 100 * (reads per sec / requests per sec) Percentage of read requests performed by the host  director. % read hit 100 * (read hits per sec / reads per sec) Percentage of read hit requests performed by the  Symmetrix host directors. Read hits occur when the read I/O operation is  satisfied directly from cache. %  utilization This metric shows how close the host director  (front-end director including Escon, fibre, or SCSI) is to 100% performance  utilization. Percentage is based on the number of I/O  operations being performed by the host director. % write 100 * (writes per sec / requests per sec) Percentage of write requests performed each  second by the host director. accumulated director  idle time Number of ticks that elapsed while the director  did not have any requests in its queue. accumulated queue  depth Sum of queue depths for the director when an  event enters this range (0 - over 640). This metric is available only for Fibre Channel  directors. average queue depth Average queue depth for the director when an  event enters this range (0 - over 640). This metric is available only for Fibre Channel  directors. device  write pending events Number of times, each second, that the  write-pending limit for a specific Symmetrix device was reached. When the limit  is reached, additional write I/O operations are deferred while waiting for data  in cache to be destaged to the disk. hits per  sec Number of read and write requests performed each  second by the host director that was immediately satisfied by  cache. ios per  sec Number of I/O operations performed each second by  the Symmetrix host director. This metric represents activity between the  Symmetrix and the host or SAN device. queue  depth count Number of events that are waiting while the  director's queue is in this range (0 - over 640). read hits per  sec (requests per sec) - (writes per sec) - (read  misses per sec) Number of read hit requests performed each second  by the Symmetrix host directors. Read hits occur when the read requests is  satisfied directly from cache. read misses  per sec Number of read miss requests performed each  second by Symmetrix host director. Read misses occur when the data requested by  the read I/O operation was not in cache, causing a wait while it was fetched  from disk. reads per  sec Number of random read requests performed each  second by Symmetrix host director. requests per  sec Number of cache slots accessed each second by  host directors. A request is the protocol used by directors (host and disk) to  marshal data to and from the cache. Requests are made up of reads and  writes. slot collisions per  sec Number of slot collisions each second. A slot  collision occurs when two or more directors try to access the same cache slot  and the slot happens to be locked for an update operation by one of the  directors. system write pending  events Number of times each second that write activity  was heavy enough to use up the system limit set for write tracks occupying  cache. When the limit is reached, writes are deferred until data in cache is  written to disk. writes per  sec Number of write requests performed each second by  the host directors.  Symmetrix port metrics The following table lists and  describes metrics for Symmetrix ports.  % utilization This metric shows how close the port performance is to  100% utilization. Percentage is the throughput in kilobytes each second  being performed by the port divided by a fixed number based on the type of  port. average io size in Kbytes (throughput in Kbytes per sec) / (ios per sec) Average number of kilobytes transferred through the  Symmetrix port per I/O operation. ios per sec Number of I/O operations performed each second by the  Symmetrix port. throughput in Kbytes per sec Number of kilobytes transferred through the Symmetrix port  (entering the Symmetrix system) each second.    Symmetrix system metrics The following table lists and describes metrics for the total  of Symmetrix systems or units.   % hit 100 * (hits per sec / total ios per sec) Percentage of I/O operations performed by all of  the Symmetrix devices, for which the read data was in cache and the write  operation could be sent directly to cache without having to wait for data to be  destaged from cache to the disks. % reads 100 * (total reads per sec / total ios per  sec) Percentage of total read I/O operations performed  each second by all of the Symmetrix devices. % sequential io 100 * (seq reads per sec / total ios per sec) Percentage of sequential I/O operations. Sequential I/O operations are a combination of  the read and write operations. A sequential read occurs when the tracks brought  into cache by prefetch tasks are read in the order in which they were put in  cache. A sequential write occurs when the data is written to cache  sequentially. % writes 100 * (writes per sec / total ios per sec) Percentage of total write I/O operations  performed by all of the Symmetrix devices. deferred writes per sec A deferred write is a write hit. A deferred write  occurs when the I/O write operations are staged in cache and will be written to  disk at a later time. delayed dfw per sec A delayed deferred fast write (DFW) is a  write-miss. A delayed DFW occurs when the I/O write operations are delayed  because the system or device write-pending limit was reached and the cache had  to destage slots to the disks before the writes could be written to  cache. destaged tracks per sec Number of tracks written per sec from cache to  disks. device max wp limit Maximum number of write-pending slots for the  entire Symmetrix. System write-pending limit is equal to 80% of the  available cache slots. Symmetrix write-pending limit is not simply a sum  of all Symmetrix device write-pending slots. It depends on other factors such as  cache size and the Symmetrix configuration. hits per sec Number of I/O operations performed each second by  all of the Symmetrix devices for which the read data was in cache and the write  operation could be sent directly to cache without having to wait for data to be  destaged from cache to the disks. ios per sec Number of I/O operations performed each second by  all Symmetrix devices including writes and random reads. In contrast, the total ios per secmetric includes writes, random reads, and sequential reads. Kbytes read per sec Number of kilobytes read by all of the Symmetrix  devices each second. Kbytes transferred per  sec (Kbytes Written per sec) + (Kbytes Read per  sec) Number of kilobytes written and read by all of  the Symmetrix devices each second. Kbytes written per sec Number of kilobytes written by all of the  Symmetrix devices each second. number format pending tracks Number of format pending tracks. number free permacache slots Number of available reserved cache  slots. number used permacache slots Number of use reserved cache slots. number write pending tracks Number of tracks in cache that are waiting to be  destaged to disk and cannot be overwritten. prefetched tracks per sec Number of tracks prefetched to cache each second  across the Symmetrix system. read hits per sec Number of read hit I/O operations performed each  second by all of the Symmetrix devices. Read hits occur when the read I/O  operation is satisfied directly from cache. reads per sec Number of random reads performed each second by  all of the Symmetrix devices. The reads per sec metric for the Symmetrix device  statistic does not include sequential reads. In contrast, the total reads per secmetric includes the random and sequential reads each second. seq reads per sec Number of sequential read I/O operations each  second. A sequential read occurs when the tracks brought  into cache by prefetch tasks are read in the order in which they were put in  cache. total ios per  sec (Random Reads per sec) + (seq reads per sec) +  (writes per sec) Total number of read I/O and write I/O operations  performed each second by all of the Symmetrix devices. total reads per sec (Random Reads per sec) + (seq reads per sec) Total number of random read and sequential read  operations performed each second by all of the Symmetrix devices. write hits per sec Number of write hits performed each second by all  of the Symmetrix devices. A write hit occurs when the I/O write operation  is received, it is immediately staged in cache and will be written to disk at a  later time. writes per sec Number of total writes performed each second by  all of the Symmetrix devices.
Hi, Can some one give the basic under standing of these perf stats and their idle values.  1.Read response time 2.Write response time 3.Hit rate 4.Miss rate  If possible pls post me a good DOC.  Thanks In Advance
performance stats