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Hardware Thread, Server replacement advice in Technical; Im liking the idea of an iSCSI SAN Should be fairly easy to convince SMT as it should reduce costs ...
  1. #16

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    Re: Server replacement advice

    Im liking the idea of an iSCSI SAN
    Should be fairly easy to convince SMT as it should reduce costs in the long term as we would have to buy less expensive replacement servers and could just upgrade the SAN each year

    Few basic (probably ignorant) questions. I did have a search but couldnt find any definative answers:

    1. For iSCSI, would it be set up as follows:
    Each server has one NIC connected to internal network, and one connected to another switch thats connected to the SAN? Drives are then mapped to each server and appear as local drives
    Thats how I understand it but I could well be wrong

    2. When you want to add an extra disk, can you just drop it in and your capacity increases just like that?

    3. Is there any redundancy if a disk fails? This is the bit that confuses me the most because it doesnt seem to be mentioned anywhere. Is there any sort of RAID built in? Or would you have to replace the disk and restore everything from backup?

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    Re: Server replacement advice

    1) Yes that's correct. You could to save cash connect to SAN Unit to your main core switch, but I would recommended purchasing a seperate switch as you suggested and connecting the servers and san to it (that's how I will be doing it). You will use the iSCSI software (probably the Windows one) to attach the drive letter to a iSCSI Target

    2) The iSCSI device will have management software and then you can add the disk and then configure the system and then if increase the size for the different 'disks'

    3) On the device you can setup RAID 5, and most should support RAID 10/50 etc. You should be able to setup a Hotswap Spare as well.

    Rob

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    Re: Server replacement advice

    A few words of caution, if you want to use ESX, then your hardware *MUST* be on the ESX hardware compatability list.

    While it uses a linux VM to manage the host, the ESX kernel itself is custom, if it's not on the list, you cannot add drivers for the device.

    I'm using 6 Dell 1855 blades with Dual Xeons 3.0 with 4GB ram. They have been in production use for around 18 months, and were bought 2 year ago. I run minimal services on each VM so that I can reboot them without affecting too much of the network at a time.

    I had to get a Fibre Channel SAN as at the time ESX did not support iSCSI, one of the reasons for the high price.

    ESX is very different from the MS and other VMware products that sit on an OS. It doesn't use SAN agent software for example and has connects itself.

    I've not done too much arranging of the VMs on the physical servers at the moment as if I find any that pull too many resources I vmotion them to another blade (one of the joys of ESX using a SAN is hot migration to another physical host of VMs).

    ESX is not for the faint of heart and it requires a lot of detailed knowledge of SANs, Fibre switches, vlans and trunking. I've managed to learn what I need to know, but it has been a bit complicated at times

    The only current issue I have is that I cannot host 64 bit VMs, as my processors are too early a revision and don't support intels VT extensions. I will live without a virtual exchange 2007 for now (although I am on 2003).

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    Re: Server replacement advice

    Have just been thinking about performance with an iSCSI SAN

    At the minute all data is stored on servers local disks, all at least 10K SCSI ones.
    A SAN (at least the Dell one ive been looking at) has only 7,200RPM disks. Plus then theres a small overhead I assume when the drives are mapped to a server.
    Also, although it would have its own dedicated switch, surely 4/5 servers all accessing the data through 1 1GB connection would be slower than it is now?

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    Re: Server replacement advice

    You can get san devices with whatever hard disks you want in them - so 15k SAS drives are possible if you are willing to pay for it.

    Remember that Hard Disk access is the slowest part of any computer, so a 1GB network connection shouldn't be a bottleneck for any normal school usage (our main file server which uses our iSCSI device only works up a sweat of ~10Mbits per second during normal hours, and 50Mbits per second when it is doing a full system backup. That is barely using the 1Gb connection really (that is with usually 70 people accessing stuff on there at the same time, scale up accordingly).

  6. #21
    zag
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    Re: Server replacement advice

    Surprised at the level of servers required in some schools, we still use basic servers with cheap big hard disks and simple hardware configurations. Creating a 1tb array is cheap these days and can be reliable. I saw an interesting article somewhere about how Google do this instead of buying expensive custom Storage solutions.

    One thing I wouldn't use is Raid for the system drive as I have had a number of problems with OS corruption over the years.

    SANs are definitely the way forward but I still think the cost benefit is not quitet there yet.

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    Re: Server replacement advice

    @ittech - Schools are supposed to be moving towards a reliable/robust system similar to those used in business. This should be done through reliable hardware and using industry standard technologies such as RAID/SANs etc... Take a look at the Becta website for information about what schools should be doing now.

    Google have created their own OS to provide distributed storage resiliance, so have spent a huge amount of money on developing this.

    Using a quick and cheap home built solution can be reliable but if it isn't, it is your arse on the line.

    Also, you should use RAID for the system drive, just use hardware raid in a mirrored fashion - if you don't use it, you simply add a large 'reinstall' time when the main disc does fail, and add a possibility of data loss due to backups not being completely in sync with the data on the drive.

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    Re: Server replacement advice

    Taking my time over the SAN so no rush for that

    But I do need to order a print server quite soon

    The one I was going to get was a Dell Poweredge 1950 (went with as many energy smart options as possible, need to try and make a bit of an effort)

    Specs:
    2x Dual Core Xeon 5148LV 2.33Ghz
    4GB RAM
    2 73GB 10,000RPM 2.5" SAS Hard Drives in RAID 1
    1U Chassis

    Would be running, as well as printers, Sophos, QCA Testing and Certificate Services

    2 things:

    a) Would a 1U chassis cause a lot more noise/heat? Because it would be extremely useful space wise

    b) Would it be sensible to get a 3rd hard disk just to use as a separate volume? As far as I can remember none of those applications recommend data on a seperate volume to the OS

  9. #24

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    Re: Server replacement advice

    Would a 1U chassis cause a lot more noise/heat? Because it would be extremely useful space wise
    It only becomes an issue when you have an entire rack of them. Twice the heat/power/etc vs 2u servers.

    Would it be sensible to get a 3rd hard disk just to use as a separate volume? As far as I can remember none of those applications recommend data on a seperate volume to the OS
    Well, when you get your SAN running this kind of stuff will live there. So with that in mind, I'd just leave the drives set as mirrored raid. If you partition the raid up into two volumes this'll make it easy to migrate your data to the SAN later on though. If you prefer to use a 2nd hard drive, I don't see why that wouldn't work to.

  10. #25

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    Re: Server replacement advice

    Very true, its hard to get out of the habit of thinking of local storage all the time!

    Thanks

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