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#11
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"Rick Denoire" wrote in message ... .... My question is, where do I have a chance to improve something? You'll need someone competent (either at EMC or with prior experience with your hardware) to answer that. At the driver level by changing the settings in the driver configuration file? About the only problem I can think of that would be outside the array would be if your driver for some reason was breaking up your large write requests into small ones which it was telling the array to execute serially. Sounds unlikely. Using the Navisphere or navicli and changing the element size or read ahead feature or ..? Read-ahead shouldn't affect your write performance. And as mentioned somewhere else, perhaps by switching the harddisk's own cache on?? Don't even think about enabling the disk's write-back cache (just in case the array isn't smart enough to turn it off again): if the controller wanted it enabled, it would be. - bill |
#12
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In article ,
Bill Todd wrote: I once again lean toward incompetence as an explanation: either the people who told you this were incompetent, or the people who implemented that FC-to-ATA translation were (there's no reason it should be anything like that slow, unless they did something incredibly dumb - or intentionally so, in order to push their higher-end solutions - and simply used their tagged-queuing SCSI algorithms unchanged with the SATA disks resulting in strictly serial/synchronous operation). It's important, of course, to understand that "translation", itself, is an extremely misleading way to describe what's actually going on inside the black box in question. It's not as if there is some magic property of Fibre Channel that causes requests for the logical volumes presented on the host side to magically flow through the controllers with no processing yielding the correct commands on the physical disk side. What you have inside a Clariion, as with any other RAID box, is a computer that is emulating a disk on one side, splitting up and otherwise processing data sent to or requested from it in the middle, and dispatching commands based on the result of that processing to physical disks on the other side. It really matters very little what the interface on the "acts like a disk" side (which faces the host) or "acts like a host" (which faces the physical disks) side are; there is no significant and fundamental economy to be gained from having them be the same. Perhaps it's a convenient explanation for some EMC engineer who just wants you to go away so he can clear the call and keep his stats up to use to blow smoke in your face; but in point of fact a Clariion with FC on one side and FC on the other is doing just as much of a "translation" as a Clariion with FC on one side and SATA on the other. Perhaps the software component that issues SATA commands to the physical disks, or even the hardware that it runs on, is not of equal quality to the one that issues FC commands to physical disks that are FC attached; but that says nothing really useful about the technology in question, only about the quality of the implementation that EMC has chosen to sell you. I note that you can buy PATA-FC and SATA-FC arrays from vendors such as NexSan which significantly outperform the numbers you're seeing (and which EMC is claiming are somehow representative of an inherent limit of this sort of configuration); these arrays also typically use higher- performance ATA disks whose cost, compared to the total margin EMC extracts from one of these boxes, is not really meaningfully larger than that of the 5400RPM, previous-generation disks that EMC insists on selling you. This, to my mind, seems to agitate towards Bill's suggestion that perhaps EMC is deliberately limiting the performance of this configuration to avoid undercutting their more expensive FC-FC arrays. -- Thor Lancelot Simon But as he knew no bad language, he had called him all the names of common objects that he could think of, and had screamed: "You lamp! You towel! You plate!" and so on. --Sigmund Freud |
#13
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Hello again
Take a look at the result of the command iostat -x /dev/emcpowerd1 5 on the Linux box. This is a LUN located on SATA disks in a RAID 5 group of 9+1 disks, no other I/O is taking place on other LUNs of the same group. These results were recorded after issuing the a command to delete about 40 files (about 200 GB all together - these are big files). While I am writing this message, the rm command is still running... after 1 hour. Incredible! I think that deleting files only removes the inodes from the metadata, so the size of the files is not so important. Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util emcpowerd1 0,00 0,00 0,80 0,00 6,40 0,00 8,00 0,00 11950,00 0,00 0,00 avg-cpu: %user %nice %sys %idle 0,00 0,00 0,12 99,88 emcpowerd1 0,00 0,00 1,20 0,00 9,60 0,00 8,00 8589934,57 7500,00 16,67 0,20 avg-cpu: %user %nice %sys %idle 0,00 0,00 0,12 99,88 emcpowerd1 0,00 0,00 0,80 0,00 6,40 0,00 8,00 0,00 11475,00 0,00 0,00 avg-cpu: %user %nice %sys %idle 0,47 0,00 0,12 99,40 emcpowerd1 0,00 0,00 1,00 0,00 8,00 0,00 8,00 0,00 11300,00 0,00 0,00 avg-cpu: %user %nice %sys %idle 0,00 0,00 0,15 99,85 emcpowerd1 0,00 0,00 1,00 0,00 8,00 0,00 8,00 0,00 9880,00 0,00 0,00 avg-cpu: %user %nice %sys %idle 0,00 0,00 0,12 99,88 emcpowerd1 0,00 1,80 7,40 0,40 59,20 17,60 9,85 8589934,57 1430,77 2,56 0,20 The average queue size does not make sense. The await time (average wait) is constantly very high. About every 30 sec, a write request takes place. I don't understand this behaviour. Any hint? Bye Rick Denoire |
#14
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EMC Clariion does not support SATA. They are PATA and have all the
issues associated with PATA (slow, unreliable, etc). IBM, STK, etc have SATA drives in their systems. - C - wrote: Hi, my company is looking at using Clariion with SATA disks for research quality storage. This means we want cheap, but still good performance. The nature of the application is to do sequential reads of many average size 3GB flat files, say 1TB at a time. So cache on the controller is useless. The raw disk throughput is more important. Write speed is important, but not as important as read. There are 2 things I am concerned with this Clariion/SATA solution... 1. Clariion's SATA drives are 5400rpm, compares to Western Digital 7200rpm. 2. The Clariion's internal signal is FC, so the SATA disks attaches to a "translator" (Can someone explain this), and this further reduces the SATA's native speed. Can someone who has experience help me out? Any story of your setup and experience are deeply appreciated. Clayton |
#15
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Joe wrote in message ...
EMC Clariion does not support SATA. They are PATA and have all the issues associated with PATA (slow, unreliable, etc). IBM, STK, etc have SATA drives in their systems. - C - wrote: Hi, my company is looking at using Clariion with SATA disks for research quality storage. This means we want cheap, but still good performance. The nature of the application is to do sequential reads of many average size 3GB flat files, say 1TB at a time. So cache on the controller is useless. The raw disk throughput is more important. Write speed is important, but not as important as read. There are 2 things I am concerned with this Clariion/SATA solution... 1. Clariion's SATA drives are 5400rpm, compares to Western Digital 7200rpm. 2. The Clariion's internal signal is FC, so the SATA disks attaches to a "translator" (Can someone explain this), and this further reduces the SATA's native speed. Can someone who has experience help me out? Any story of your setup and experience are deeply appreciated. Clayton Jo - I have to wonder if you are the same FUD-starter as the person who keeps spreading all the manure on the emc group on ITtoolbox.com. It seems a little supect to me that a user Jo_ratner seems to be posting the same messages in that group as you are in this group ( and the similarity in your username seems to be a further coincidence). Why don't you just disclose your vendor affiliation. I guess it is HDS since most of the FUD seems rather dated and incorrect. It's unfortunate that people with an agenda can disturb those looking for user group type feedback. It's the same flamebait / vendor bashing that makes slashdot and the like barely worth following. I used to find groups like this a trusted forum where I could get some good information when needed; usually from a few specific contributors ( Boll, Bill ) that improved the level of discussion. Lastly, i wish you luck in your anti-EMC crusade. While they are far from perfect, I just have no use for vendor bashing. Hopefully you never show up at my shop- you'll be the first to leave. |
#16
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WHAT? Clayton was talking abot Clariion SATA drives. All I did was
point out that the CX series uses PATA today (SATA next quarter I think but am not sure). That is not "FUD". I have no idea what the rest of the crap you said means. BTW, I do own EMC gear bought late last year. Why would I bash EMC? Flogi wrote: Joe wrote in message ... EMC Clariion does not support SATA. They are PATA and have all the issues associated with PATA (slow, unreliable, etc). IBM, STK, etc have SATA drives in their systems. - C - wrote: Hi, my company is looking at using Clariion with SATA disks for research quality storage. This means we want cheap, but still good performance. The nature of the application is to do sequential reads of many average size 3GB flat files, say 1TB at a time. So cache on the controller is useless. The raw disk throughput is more important. Write speed is important, but not as important as read. There are 2 things I am concerned with this Clariion/SATA solution... 1. Clariion's SATA drives are 5400rpm, compares to Western Digital 7200rpm. 2. The Clariion's internal signal is FC, so the SATA disks attaches to a "translator" (Can someone explain this), and this further reduces the SATA's native speed. Can someone who has experience help me out? Any story of your setup and experience are deeply appreciated. Clayton Jo - I have to wonder if you are the same FUD-starter as the person who keeps spreading all the manure on the emc group on ITtoolbox.com. It seems a little supect to me that a user Jo_ratner seems to be posting the same messages in that group as you are in this group ( and the similarity in your username seems to be a further coincidence). Why don't you just disclose your vendor affiliation. I guess it is HDS since most of the FUD seems rather dated and incorrect. It's unfortunate that people with an agenda can disturb those looking for user group type feedback. It's the same flamebait / vendor bashing that makes slashdot and the like barely worth following. I used to find groups like this a trusted forum where I could get some good information when needed; usually from a few specific contributors ( Boll, Bill ) that improved the level of discussion. Lastly, i wish you luck in your anti-EMC crusade. While they are far from perfect, I just have no use for vendor bashing. Hopefully you never show up at my shop- you'll be the first to leave. |
#17
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Joe wrote in :
EMC Clariion does not support SATA. They are PATA and have all the issues associated with PATA (slow, unreliable, etc). IBM, STK, etc have SATA drives in their systems. PATA drives are no better or worse for that application than SATA. The Clariion does it by using an internal PATA-to-dual-SATA converter and two SATA-to-FC converters connecting to each back-end loop. Works out just fine for us, so far. -- /Jesper Monsted |
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