On 08/02/13 10:48, Chris Murphy wrote:

***On Feb 7, 2013, at 6:08 AM, Adam Goryachev
[off-list ref] wrote:

quoted

Basically, on occasion, when a user copies a large file from disk
to disk, or when a user is using Outlook (frequently data files are
over 2G), or just general workload, the system will "stall",
sometimes causing user level errors, which mostly affects Outlook.

Does this concern anyone else? In particular the user doing "disk to
disk" large file copies. What is this exactly? LV to LV with iSCSI
over 1gigE? Why did you reject NFS for these physical Windows boxes
and their VMs to access this storage, rather than what I assume is
NTFS over iSCSI, because of this statement?

This isn't a common thing (well, it happens once a week when a user logs
in after hours to do some sort of backup/DB maintenance), but it is the
easiest way to reproduce the problem, and from the evidence, it seems to
match.

ie, generally the problem is characterized as:
1) Large amount of read and write on one iSCSI device
2) User complain about write failures, slow response, etc even when 1
and 2 are on different VM's (which are on different physical machines).

quoted

Each LV is then exported via iSCSI

That block device needs a file system for Windows to use it.

It also seems to me one or more of these physical servers running
VMs, with only 1gigE to the storage server, need either additional
pipes LACP or bonded ethernet, or 10gigE. I can just imagine one
person doing a large file copy disk to disk, which is a single pipe
doing a pull push, double NTFS packet overhead, while all other
activities get immensely hit with network latency as a result.

However, this should only cause issues for users on the server which is
doing this. ie, if a user logs into terminal server 1, and copies a
large file from the desktop to another folder on the same c:, then this
terminal server will get busy, possibly using a full 1Gbps through the
VM, physical machine, switch, to the storage server. However, the
storage server has another 3Gbps to serve all the other systems. Also,
100MB/s is not an unreasonable performance level for a single system
(ok, minus overhead, even 60MB/s would probably equal what they had
before with 10 year old SCSI disks).

###On Feb 7, 2013, at 4:07 AM, Dave Cundiff [off-list ref]
wrote:

quoted

See page 17 for a block diagram of your motherboard… Your SSDs 
alone could saturate that if you performed a local operation. Get
your NIC's going at 4Gig and all of it a sudden you'll really want
that SATA card in slot 4 or 5.

Yeah I think it needs all the network performance and reduced latency
as he can get. I'll be surprised if the SSD tuning alone makes much
of a dent with this.

I still need to go in (tomorrow night) and pull apart the machine
physically to confirm which slot the network cards are in, but based on
the other comments, I don't think this is the limiting factor.... Slap
me if it is and I'll drive in tonight and check it sooner.

Thanks,
Adam

-- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au
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