Well, for one thing I believe the fiber channel supports 1Gb/second, This is
one gigabit per second and you are talking about 500 gigabytes of data. I
look at fiber channel as 100MB/second. So even if the VA7100 was going at
full blast, it would take 5,000 seconds to transfer all the data, a little
under one and one half hours.
But the VA7100 does not transfer or receive at 100MB/second, it can, but the
3000 won't let it do it. Now, since the VA7100 can blast out at 90MB/second
(as an array, not from a single drive,) and the VA7110 has a maximum output
of 160MB/second, I would venture to say that a sustained read or write from
a VA7100 going through a 3000 as it does file copies, will probably max out
at around 30-40MB/second. Just a guess. By the way, the rated write speed
of the VA7100 is 45MB/second, and 84MB/second for the VA7110.
So you say, but Denys, the write speed is about half of the read speed, so
your restore should take twice as long as your backups.
Not really, you have to consider the medium to which you are backing up.
Now Tim did not mention the medium he uses, but I would guess he has
DLT8000s. Maybe just one. He should be able to drive that puppy on an
uncrippled N-class box at 12+MB/second. You will notice this value is a lot
less than either the read or write speed of the VA71xx.
Given an uncrippled N-class and some proper backup software, you can expect
a lot higher throughput rate going to LTO devices. At that point, he might
be able to do the backup of 500GB in less than 6 hours.
I just looked at the original post and notice 2 things. 1- Tim did not
mention how much data he is talking about, just 19 hours for backup. 2- The
listing did show 38 volumes in the set. I suggest he may not want quite
that many on the VA71xx, maybe 16.
If Tim uses a DLT8000 to do his backups, he has at most 800GB of data; if he
uses (shudder) DDS-3 to do the backup, he has much less data, around
400-500GB at most. Compression will help especially in the case of massive
IMAGE databases.
Denys
-----Original Message-----
From: Craig Lalley [mailto:[log in to unmask]]
Sent: Monday, February 21, 2005 8:59 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re: Moving from XP512 to VA71xx
--- Denys Beauchemin <[log in to unmask]> wrote:
>
> And if your restore takes twice as long as your backup, you have
> opportunities for improvement.
>
Denys,
I think you have an excellent idea of moving one group at a time.
Given that there is 500Gb of data to move accross a 1GB fiber path... Where
is the real
bottleneck?
Relatively speaking, I would find it hard to believe that on a 1GB fiber
path, it would really
take that long to transfer the data.
So what is the REAL throughput of a 1GB channel?
-Craig
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