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• ZFS and SAN -- best practices?

  - by chris

  Most discussions of ZFS suggest that the hardware RAID be turned off and that ZFS should directly talk to the disks and manage the RAID on the host (instead of the RAID controller). This makes sense on a computer with 2-16 or even more local disks, but what about in an environment with a large SAN? For example, the enterprise I work for has what I would consider to be a modest sized SAN with 2 full racks of disks, which is something like 400 spindles. I've seen SAN shelves that are way more dense than ours, and SAN deployments way larger than ours. Do people expose 100 disks directly to big ZFS servers? 300 disks? 3000 disks? Do the SAN management tools facilitate automated management of this sort of thing?

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• Using 2-port LSI 2308-8e card to control 24 SAS HDDs

  - by GregC

  I would like to rely on a RAID-on-chip solution to control 24 SAS hard drives in a direct-attached environment. How would you approach this to get best bandwidth given that I'd like to spend less than $10,000 on the interconnect. I've read that LSI 2308 chip can easily handle 8-drive SSD RAID6 in hardware. I'd like to harness its power to control 24 SAS hard drives over an expander in an external enclosure. Currently I use an Infortrend S24S-G2240 external enclosure. It provides its own controller and expander. I'd like to use LSI 2308 controller for RAID6 somehow instead of the mystery controller in the enclosure. P.S. I tried to create SAS-expander as a tag, but my rep on this site is low.

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• SAS(Statistical Analysis System) Career As a computer science student

  - by Renju

  Hi. I have completed MSc in Computer science this academic year. So I am fresher... While I am doing graduation and post graduation I did many projects using PHP and MySQL. Now I got opportunity to get into SAS(Statistical Analysis System) career, and I heard that SAS having better career growth than PHP developement. For the past 4 days, I was working with SAS and I feel interested in working. My questions are, Since i am a computer science student whether i will have any problem in my career growth in SAS? I am ready to learn statistics also, is there anything else I have to do? Doing certification in SAS will make any changes? Is it a bad idea to get into SAS with only CSc backgrond? So please guide me for my career...

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• Are FC and SAS DAS devices standard enough?

  - by user222182

  Before I ask my questions, here is some background info that may or may not be useful: For the first time I find myself needing a DAS solution. My priority is data through-put in a single direction. I can write large blocks, and I don't need to read at the same time. The server (the data producing device) is not really a typical server, its a very powerful single board computer. As such I have limited options when it comes to the add-in cards I can install since it must use the fairly uncommon interface, XMC. Currently I believe I am limited PCIex8 gen 1 which means that the likely bottle neck for me will be this 16gbps connection. XMC Boards I have found so far offer the following connections: a) Dual 10GBE ethernet controller, total throughput 20gbps b) Dual Quad SAS 2.0 Connectors (SFF-8XXX) HBA (no raid), total throughput 48 gbps c) Dual FC 8gb HBA (no raid), total throughput 16gbps My questions for you guys are: 1) Are SAS and/or FC, and by extension their HBAs, standard enough that I could purchase a Dell or Aberdeen storage server with a raid controller that has external SAS or FC ports and expect that I can connect it to my SAS or FC HBA, be presented with a single volume (if I so configured the storage server), all without having to check for HBA compatibility? 2) On a device like a Dell PowerVault (either DAS or NAS) is there an OS on it to concern myself with, or is it meant to be remotely managed? Is there a local interface in case I cant remotely manage it (i.e. if my single board computer uses an OS not supported by Dell OpenManage). Would this be true of nearly any device which calls itself a DAS? 3) If I purchase some sort of Supermicro storage chassis, installed a raid controller with external connections, is there a nice lightweight OS I can run just for management of the controller? Would I even need an OS since the raid card would be configured pre-boot anyway? 4) It is much easier to buy XMC based 10gigabit ethernet cards (generally dual port). In what ways would I be getting into trouble by using iSCSI as a DAS are direct cabling with SFP+ cables? Thanks in advance

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• HP DL180 and External SAS Tape Backup Drive

  - by Jonathan

  Is is possible to use the following PCI-E card with a HP DL180 server (specifically the 487507-371 model) - HP 4x Internal/4x External SAS PCI-E Adapter (416096-B2). If not what are the options for attaching an external SAS tape drive?

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• Determine the folder of a SAS source file

  - by exhuma

  When I open a SAS file in enterprise guide and run it, it is executed on the server. The source file itself is located either on the production site or the development site. In both cases, it is executed the same server however. I want to be able to tell my script to store results in a relative folder. But if I write something like libname lib_out xport "..\tmp\foobar.xpt"; I get an error, because the working folder of the SAS Enterprise Guide process is not the location of my source file, but a folder on the server. And the folder ..\tmp does not exist there. Even if it would, the server process does not have write permission in that folder. I would like to determine from which folder the .sas file was loaded and set the working folder accordingly. In one case it's S:\Development\myproject\sas\foobar.sas and in the other case it's S:\Production\myproject\sas\foobar.sas It this possible at all? Or how would you do this?

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• R glm standard error estimate differences to SAS PROC GENMOD

  - by Michelle

  I am converting a SAS PROC GENMOD example into R, using glm in R. The SAS code was: proc genmod data=data0 namelen=30; model boxcoxy=boxcoxxy ~ AGEGRP4 + AGEGRP5 + AGEGRP6 + AGEGRP7 + AGEGRP8 + RACE1 + RACE3 + WEEKEND + SEQ/dist=normal; FREQ REPLICATE_VAR; run; My R code is: parmsg2 <- glm(boxcoxxy ~ AGEGRP4 + AGEGRP5 + AGEGRP6 + AGEGRP7 + AGEGRP8 + RACE1 + RACE3 + WEEKEND + SEQ , data=data0, family=gaussian, weights = REPLICATE_VAR) When I use summary(parmsg2) I get the same coefficient estimates as in SAS, but my standard errors are wildly different. The summary output from SAS is: Name df Estimate StdErr LowerWaldCL UpperWaldCL ChiSq ProbChiSq Intercept 1 6.5007436 .00078884 6.4991975 6.5022897 67911982 0 agegrp4 1 .64607262 .00105425 .64400633 .64813891 375556.79 0 agegrp5 1 .4191395 .00089722 .41738099 .42089802 218233.76 0 agegrp6 1 -.22518765 .00083118 -.22681672 -.22355857 73401.113 0 agegrp7 1 -1.7445189 .00087569 -1.7462352 -1.7428026 3968762.2 0 agegrp8 1 -2.2908855 .00109766 -2.2930369 -2.2887342 4355849.4 0 race1 1 -.13454883 .00080672 -.13612997 -.13296769 27817.29 0 race3 1 -.20607036 .00070966 -.20746127 -.20467944 84319.131 0 weekend 1 .0327884 .00044731 .0319117 .03366511 5373.1931 0 seq2 1 -.47509583 .00047337 -.47602363 -.47416804 1007291.3 0 Scale 1 2.9328613 .00015586 2.9325559 2.9331668 -127 The summary output from R is: Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 6.50074 0.10354 62.785 < 2e-16 AGEGRP4 0.64607 0.13838 4.669 3.07e-06 AGEGRP5 0.41914 0.11776 3.559 0.000374 AGEGRP6 -0.22519 0.10910 -2.064 0.039031 AGEGRP7 -1.74452 0.11494 -15.178 < 2e-16 AGEGRP8 -2.29089 0.14407 -15.901 < 2e-16 RACE1 -0.13455 0.10589 -1.271 0.203865 RACE3 -0.20607 0.09315 -2.212 0.026967 WEEKEND 0.03279 0.05871 0.558 0.576535 SEQ -0.47510 0.06213 -7.646 2.25e-14 The importance of the difference in the standard errors is that the SAS coefficients are all statistically significant, but the RACE1 and WEEKEND coefficients in the R output are not. I have found a formula to calculate the Wald confidence intervals in R, but this is pointless given the difference in the standard errors, as I will not get the same results. Apparently SAS uses a ridge-stabilized Newton-Raphson algorithm for its estimates, which are ML. The information I read about the glm function in R is that the results should be equivalent to ML. What can I do to change my estimation procedure in R so that I get the equivalent coefficents and standard error estimates that were produced in SAS? To update, thanks to Spacedman's answer, I used weights because the data are from individuals in a dietary survey, and REPLICATE_VAR is a balanced repeated replication weight, that is an integer (and quite large, in the order of 1000s or 10000s). The website that describes the weight is here. I don't know why the FREQ rather than the WEIGHT command was used in SAS. I will now test by expanding the number of observations using REPLICATE_VAR and rerunning the analysis.

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• SAN typical MTBF

  - by Adrian K

  We're using a SAN on a project at work, and there's a bit of debate around the fact that's technically it's a Single Point of Failure. No one seems to have any hard data. The SAN in question is a single physical box, but with internal redundant components (sorry - not sure3 what level of RAID it has, but I can find out). What's the tyopical MTBF for a SAN? The PM has it down on the projects risk register as "Quite Common' - I've never heard of a SAN going down, but I don't jhave any stats to show how likely it really is. Does anyone have any helpful info?

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• Win'08 - Extend volume size on SAN attached storage in a failover cluster

  - by user53207

  Running Win 2008, I'd like to extend the volume of a SAN attached drive that is part of a failover cluster. The SAN team has allocated additional drive space which is being seen by Windows Storage Manager. However, the option to "Extend Volume" is disabled, so is the ability to turn it into a dynamic disk. Is the ability to extend volumes when part of a failover cluster disabled or not available when it's part of SAN attached storage?

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• Which protocol do clients use when communicating with servers in a SAN

  - by Mario De Schaepmeester

  I'm trying to wrap my head around how a SAN works and how it is implemented. If I understand this well, clients wanting to access the storage devices in a SAN need to communicate with the servers via the LAN. When the SAN is implemented with Fibre Channel, these servers are Fibre Channel compliant devices, and internally in the SAN they work with the Fibre Channel Protocol. Both data and communications are supported by Fibre Channel. But which application-layer protocol do the clients use in the LAN to communicate with the servers? Is the data simply transferred via ethernet as well? This is some part I am stuck on. I went trough a lot of sources but most sources don't really mention protocols and if they do, they only mention FCP.

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• SAN alternative for VMWare

  - by CogitoErgoSum

  Has anyone utilized something aside from a SAN to run their VMWare images off? We are looking to drop in two HP Servers and VMWare on them and run them off a SAN. Due to the cost of SAN though our CFO and VP are wondering if there are any viable alternatives (I.e. NAS) that can effectively run a VMWare. I can't think of any off of the top of my head. IF anyone can provide one or a good article outlining why to stick to SAN that'd be great.

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• ESX hosts lose connectivity with iSCSI SAN LUNs

  - by Themist

  I've been experiencing this issue for a couple of months now where my ESX hosts lose connectivity with my iSCSI SAN vmfs volumes. As a results the ESX hosts enter a nonresponsive mode the associated VMs disconnect and the only remedy is to reboot the host. This issue happens randomly . I have escalated this issue with VMWare but I haven't had any solution to the issue yet. I see no errors on my switches and there are no hardware issues as well. My SAN infrastucture is solid and there are 2 paths for every vmfs volume. Did anybody else experienced a similar issue? edit: Here are some more details: The iSCSI SAN software is Datacore Sanmelody 2.0.4.2 running on 2 HP Proliant G5 servers. The storage attached to each of the servers is an HP MSA70 and all the iSCSI SAN Volumes that are presented to my 4 ESX hosts are mirrored. I have two iSCSI swithces HP Procurve 1800G-24 that are trunked together. My SANLELODY servers are using NC360T NICs. I team two NICs and have one cable connecting to each iSCSi switch. Each ESX server uses two NICs as well for the iSCSI Network.

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• Need help trying to diagnose Symmetrix SAN performance issues

  - by arcain

  I am helping to benchmark hardware for a new SQL Server instance, and the volume presented to the OS for the data files is carved from a set of spindles on a Symmetrix SAN. The server has yet to have SQL Server installed, so the only activity on the box is our benchmarking. Now, our storage engineers say that this volume and it's resources are dedicated to our new server (I don't have access to see the actual SAN config) however the performance benchmarks are troubling. For example, the numbers look good until suddenly, and randomly, we see in our IO benchmarking tool wait times of 100 seconds, and disk queue lengths of 255 in perfmon. This SAN has an 8 GB cache, plus there are other applications besides ours that use the SAN. I'm wondering if (even though the spindles for our volumes should be dedicated to us) the cache may be getting hammered during the performance testing, or perhaps the spindles our volumes are on aren't really dedicated to us. We're not getting much traction from our storage engineers in helping us track down the problem, so if anybody has experience with diagnosing a problem like this and would like to share insights and troubleshooting methodologies, I'd appreciate it.

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• Why do you use a 3PAR SAN? [closed]

  - by Starfish

  If you use a 3PAR SAN, I’d like to hear what you think about it, particularly compared to the HP EVA. What do you see as its advantages over other SANs like the EVA? What’s so special about the ASIC? We had HP quote us an EVA P6500 and 3PAR V400 with equivalent storage and the 3PAR was nearly twice the cost. My site has two EVA SANs with a combined capacity of ~80 TB. We want to replace the older and larger of the two. We’ve been looking at the EVA and the 3PAR to see which would be a better fit for us. I’m struggling to understand how the 3PAR differs from the EVA from a practical technical standpoint. When I read the sales literature and speak with the HP sales engineers, they spend a lot of time talking about how the 3PAR is better because of its ASIC. It’s ASIC this and ASIC that, but when I press them on how a 3PAR with thin provisioning is better than an EVA with thin provisioning, I can’t get a straight answer. Meanwhile, one of my colleagues, who has more say regarding which SAN we get, is enamored by the 3PAR, and he can’t explain clearly to me why he wants it over the EVA. Our needs are pretty simple. We have 10 servers running VMware and ~100 VMs. We use VMware’s thin provisioning currently, but we would like to start using thin provisioning on the new SAN. We don’t have a need for SSDs or migration between storage tiers. We plan on having FC or SAS drives for our most used data and SATA/FATA drives for the lesser used data which is how we have the EVAs configured. We also do not need any SAN-level snapshotting or replication.

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• SAS Expanders vs Direct Attached (SAS)?

  - by jemmille

  I have a storage unit with 2 backplanes. One backplane holds 24 disks, one backplane holds 12 disks. Each backplane is independently connected to a SFF-8087 port (4 channel/12Gbit) to the raid card. Here is where my question really comes in. Can or how easily can a backplane be overloaded? All the disks in the machine are WD RE4 WD1003FBYX (black) drives that have average writes at 115MB/sec and average read of 125 MB/sec I know things would vary based on the raid or filesystem we put on top of that but it seems to be that a 24 disk backplane with only one SFF-8087 connector should be able to overload the bus to a point that might actually slow it down? Based on my math, if I had a RAID0 across all 24 disks and asked for a large file, I should, in theory should get 24*115 MB/sec wich translates to 22.08 GBit/sec of total throughput. Either I'm confused or this backplane is horribly designed, at least in a perfomance environment. I'm looking at switching to a model where each drive has it's own channel from the backplane (and new HBA's or raid card). EDIT: more details We have used both pure linux (centos), open solaris, software raid, hardware raid, EXT3/4, ZFS. Here are some examples using bonnie++ 4 Disk RAID-0, ZFS WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 194MB/s 19% 92MB/s 11% 200MB/s 8% 310/sec 194MB/s 19% 93MB/s 11% 201MB/s 8% 312/sec --------- ---- --------- ---- --------- ---- --------- 389MB/s 19% 186MB/s 11% 402MB/s 8% 311/sec 8 Disk RAID-0, ZFS WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 324MB/s 32% 164MB/s 19% 346MB/s 13% 466/sec 324MB/s 32% 164MB/s 19% 348MB/s 14% 465/sec --------- ---- --------- ---- --------- ---- --------- 648MB/s 32% 328MB/s 19% 694MB/s 13% 465/sec 12 Disk RAID-0, ZFS WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 377MB/s 38% 191MB/s 22% 429MB/s 17% 537/sec 376MB/s 38% 191MB/s 22% 427MB/s 17% 546/sec --------- ---- --------- ---- --------- ---- --------- 753MB/s 38% 382MB/s 22% 857MB/s 17% 541/sec Now 16 Disk RAID-0, it's gets interesting WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 359MB/s 34% 186MB/s 22% 407MB/s 18% 1397/sec 358MB/s 33% 186MB/s 22% 407MB/s 18% 1340/sec --------- ---- --------- ---- --------- ---- --------- 717MB/s 33% 373MB/s 22% 814MB/s 18% 1368/sec 20 Disk RAID-0, ZFS WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 371MB/s 37% 188MB/s 22% 450MB/s 19% 775/sec 370MB/s 37% 188MB/s 22% 447MB/s 19% 797/sec --------- ---- --------- ---- --------- ---- --------- 741MB/s 37% 376MB/s 22% 898MB/s 19% 786/sec 24 Disk RAID-1, ZFS WRITE CPU RE-WRITE CPU READ CPU RND-SEEKS 347MB/s 34% 193MB/s 22% 447MB/s 19% 907/sec 347MB/s 34% 192MB/s 23% 446MB/s 19% 933/sec --------- ---- --------- ---- --------- ---- --------- 694MB/s 34% 386MB/s 22% 894MB/s 19% 920/sec 28 Disk RAID-0, ZFS 32 Disk RAID-0, ZFS 36 Disk RAID-0, ZFS More details: Here is the exact unit: http://www.supermicro.com/products/chassis/4U/847/SC847E1-R1400U.cfm

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• SAS: add comment to lst ouput file

  - by Dan

  In SAS, How do I add comments to my .LST output file. Like adding a comment saying "This is the output for tbl_TestMacro:" right before doing a proc print? So that my output file will read: This is the output for tbl_TestMacro: Obs field1 field2 1 6 8 2 6 9 3 7 0 4 7 1 Instead of just: Obs field1 field2 1 6 8 2 6 9 3 7 0 4 7 1 Thanks, Dan

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• Install SAS/SATA backplane in Dell PowerVault 220S

  - by e151280

  Is the backplane of a Dell PowerVault 220S svc tag 3sdpcb1 (14 drive, 80 pin hot swap scsi) upgradeable to a SAS/SATA backplane & controller card replacement? The unit already seems to be quite modular, with slide-out replaceable scsi controllers/connectors on the back, and slide out redundant power supplies. With everything else so modular, the backplane would seem to be the next logically upgradeable part of this unit. Thanks in advance for your input

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• "Raid 0 SAS" versus "2nd generation SSD"

  - by Stefano

  Hi everybody, i was planning to buy a SAS system made of two 15k RPM disks in Raid 0 configuration to give a boost to my s.o. and my apps... but after i saw that article on Coding Horror, i've started to thinking if a new 2nd generation SSD could do the same job, or even better... Does anybody have any information to help me decide?

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• iSCSI SAN RAID 10 Performance -- Poor Read, Good Write

  - by Litzner

  I have a EqualLogic PS4000 SAN unit with the latest firmware, setup in RAID 10. I have 3 2TB Volumes on the SAN shared out via iSCSI on 2 eth ports on two different subnets. I have moved a test server over to this newly setup SAN, and my testing is showing me a problem. I am getting dismal read performance in everything except a test with 32 queue depth (see attach image) Write performance seems to be right about where it should be. I have tried MPIO on and off, on was slightly better but not much.

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• Should I install software on a "SAN"

  - by am2605

  Hi, I need to set up ColdFusion 9 on a ubuntu server that has a SAN disk mounted. Is it appropriate to install the CF server software on this disk? I don't really understand the ins and outs of what a SAN is, so I am not sure if the intention is for me to solely install web content on it or whether the server software itself should go here too. Any advice would be extremeness welcome. Many thanks, Andrew.

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• Hyper-V 2012 and P2000 SAS SAN

  - by user155950

  Hi I am having major problems setting up a Hyper-V 2012 cluster on a P2000 SAS SAN. Running System Center VMM 2012 SP1 I am unable to see any storage to create my cluster. Has anyone had experienced anything similar? Under fabric and storage I can't add the P2000, all I can do is use storage spaces in server manager to create a storage pool and virtual disk. This allows me to create a file share which I can add to VMM but I still can't see any disk to create a cluster. I am just about at the point where I want to tear my hair out wipe the servers and stick VMware on them because I know it works as I have set several systems up like this in the past. The Hyper-V servers can see the storage and in server manager on my management machine it seems to know both servers can see the same disk. VMM is running on the same machine and it can't see any disk. Help..... Thanks Mike

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• Do 10m external SAS cables work?

  - by Joachim Sauer

  According to the Wikipedia page external SAS cables are specified for up to 10m length. However, I found it pretty hard to actually find places that sell cables of that length. This made me wonder: Are there any known problems with using cables that are as long as this? Will it be more fragile? Slower? And if 10m is not suggested, would 6m be any more stable? A little background: for several reasons we'd like to put a tape library physically separate from our main server and 10m would be enough to put it on a separate floor.

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• Considerations for spanned volumes with SAN's LUN.

  - by Patrick Pellegrino

  I want to know, before going forward, what I can expected in lost of performance (or not) of creating Windows spanned volumes from LUN delivered by a SAN ? I don't know which kind of SAN is (we don't administer it), but they give us 10 300 Gb LUN to our Windows 2k8 R2 (Vmware) and we need larger volume so we think to spanned some disk but we are aware of the performance issue. Any input ? Regards.

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• Intel SASWT4I SAS/SATA Controller Question

  - by Joe Hopfgartner

  Hey there! I want to assemble a cheap storage sytem based on the Norco RPC-4020 Case. When searching for controllers I found this one: Intel® RAID Controller SASWT4I This is a quote form the Spec Sheet: Scalability. Supports up to 122 physical devices in SAS mode which is ideal for employing JBODs (Just a Bunch Of Disks) or up to 14 devices in RAID 0, 1, 1E/10E mode through direct connect device attachment or through expander backplane support. Does that mean I can attatch 14 SATA drives directly to the controller using SFF-8087 - 4x SATA breakout cables? That would be nice because then I can choose a mainboard that has 6 Onboard SATA and i can connect all 20 bays while only spending 155$ on the controller and like another 100$ on cables. Would that work? And why is it 14 and not 16 when there are 4 Ports? I am really confused about all the breakout/fanout/(edge-)expanding/multiplying/channel stuff...

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• cPanel web servers mounting home partition to a NAS or SAN

  - by Scott

  Hello, I currently have 2 cPanel web servers that are little 1RU dual cpu quad core xeons. They have a lot of resources for processing and handling web requests, and never exceed more than 10% cpu usage. They also have plenty of RAM. The problem is though that they both have RAID 1 160Gb SAS hard disk drives in them that are 75% full, and growing by the day. I didnt think that the amount of disk usage would be so high, but due to the nature of the sites hosted, this has become an issue. The easy fix would be just to upgrade the hard drives to something bigger (probably not of the SAS variety), but I am thinking of keeping the current machines as "processing servers" and buying a central "storage server" with about 12TB of storage. The /home/ partition on each of the 1RU servers would be mounted to a NAS or SAN point on this central storage server. My questions are: - Has anyone got a cPanel setup where they mount /home/ to a NAS or SAN elsewhere? If so, can you provide details as to what you did and how it went :) - Any recommendations on networking? Is gigabit ethernet enough? Is TCP/IP going to be a noticable performance problem? Anyone used a TOE key? - Anyone benchmarked or had any performance issues with SAN over NAS? Any help greatly appreciated. Scott

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