Maybe this will help...
What we did with our CDLs and we are happy with it:
- We defined a Scalar i2000 tape library
- 8 SDLT tape drives in each VTL (2 CDLs per TSM server(long story))
We did eight drives in library because we calculated that would be about
all our hardware could handle when doing Backup Storage pool to our
physical 3590E drives. It is never a good idea to starve an actual tape
drive.
We wanted a different virtual tape drives so we would not have any
driver version conflicts with the physical tape drives.
- 100GB cartridges. The consultant said that was a good size, it works
and we did not try any other sizes.
We backup to disk pools unless the file is greater than 2GB. This was
little slower to tape because of the stops and starts.
We do compression on the CDL and get nearly 2:1 on average. This makes
VTL better than straight disks.
We let TSM do all data movement. We do not have the CDL do any tape to
tape copies.
A backup takes the path of: Host --> AIX_Disks --> CDL
All copy tapes are physical tapes.
Each TSM server moves about 2TB per night.
When we added the CDL's, we "simply" changed where our primary tape
pools where and waited our retention period for attrition to reduce the
primary tapes, then moved the rest to the CDL. Reclaiming to a
different pool is a really nice feature.
This config may change when we do our server refresh this year.
Andy Huebner
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Joni Moyer
Sent: Friday, June 08, 2007 2:02 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] How to Incorporate a CDL into TSM environment?
Hi Everyone,
I have 1 question about the order of the steps that I must take to fold
the CDL into an environment where I will still have a disk storage pool,
but will migrate the data to the cdl and hold it there for 30 days
before
moving it to physical tape media. (Which in my case is LTO2.)
Here is what I have planned so far when we implement this:
Define CDL library (Emulating IBM 3584)
Define path from the server to the CDL library
Define drives (Emulating LTO2)
Define drive paths
Define device class for LTO2
Define primary storage pools with hi=90, lo=70, migdelay=30, next=tape
stgpool
Label tapes: label libvol library_name search=yes checkin=scratch
volrange=A00000,A00203
Update the disk storage pools so that they have a next storage pool
directed to the cdl storage pool
After this point I'm a little confused as to when migrations & the
backups
of the pools should be done and in what order.
So, for example:
AIX --> disk stgpool
AIX_CDL --> cdl sequential access stgpool
AIX_TAPE --> sequential access stgpool LTO2
AIX_COPY --> offsite stgpool LTO2
Would I do the following? I guess I'm getting a little confused on
exactly what order of operations would be best?
Client bkups to AIX pool
After 24 hrs. migrate AIX pool to AIX_CDL pool
Backup stgpool AIX_CDL to AIX_COPY
Backup stgpool AIX to AIX_COPY
Migrate data to AIX_TAPE after 30 days
Backup stgpool AIX_TAPE to AIX_COPY
Also, I have heard that you can turn compression on at the CDL drive
level. I have purchased an EMC CDL 4400. Would it be best to turn
compression on at this level? Or is it possible to define the device
class with ultrium2c instead of just ultrium2?
Or should I just turn TSM client compression on the larger servers such
as
Oracle databases and Lotus Notes? I don't want to have too negative of
a
performance impact, but yet I can't afford to not compress anything...
I'm trying to wrap my brain around this whole concept and the best
methods/practices to use the CDL. Any thoughts/opinions are greatly
appreciated!
********************************
Joni Moyer
Highmark
Storage Systems, Storage Mngt Analyst III
Phone Number: (717)302-9966
Fax: (717) 302-9826
joni.moyer AT highmark DOT com
********************************
"Prather, Wanda" <Wanda.Prather AT JHUAPL DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
06/08/2007 02:25 PM
Please respond to
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
To
ADSM-L AT VM.MARIST DOT EDU
cc
Subject
Re: How to Incorporate a CDL into TSM environment?
You go John!
(And a BIG ditto on the compression rate issue - I've NEVER had a
customer
that got 3:1 over the whole TSM environment.)
And let's step back a minute for a sanity check and ask, what IS a VTL
anyway?
It's disk with some cache and software in front.
So if you need to back up 20 TB of disk, why not do as Kelly says and
just
buy another 20 TB of disk?
Answer:
In most cases, people buy a 20TB VTL because it's cheaper than adding
another 20 TB in their disk array of choice.
Why do you think that is? Is it because the vendors are really nice
guys?
Well, they may be really nice guys, but it's not because they want to
give
disk away.
It's because the VTLs are built of A LESS EXPENSIVE KIND OF DISK.
The cheaper disk is slower.
Using cheaper disk, the VTL vendors have made it practical and cost
effective to eliminate tape backups, FOR SOME CUSTOMERS.
When people say they can back up or restore with a VTL faster than tape,
it may mean
1) they are replacing slow tape drives
2) they are eliminating tape mount times
3) they no longer have to wait for a tape drive
It doesn't mean there aren't cases where tape is faster.
There are cases where a VTL really rocks. My favorite is using a VTL
for
OFFSITE storage and backing up to it directly over fibre. In case of a
major problem, you aren't limited in the number of tape drives you have
available for restore (you ARE still limited by the size of your fibre
pipe). You don't have to physically move tapes around, and the media
never leaves your control (If I never spend another minute doing a
manual
audit looking for misplaced tapes...etc.). And you don't have to
collocate in a VTL, since there is zero effective tape mount time. And
it
is a good solution for people who want to do more Lan-free backups, and
are short of tape drives.
But you should be buying a VTL for one of THOSE reasons, not for raw
speed.
You can always create a scenario where you get down to the actual device
speed of the underlying technology and hit that bottleneck. Many people
never run into that scenario. But some do.
Also, FWIW, tape is still cheaper per MB of storage than a VTL. There
are
price points where they are comparable, or where the benefits of a VTL
outweigh the cost differential. But in general, the larger your site in
terms of TB to store, the more difference you will see in cost if you go
with a VTL vs. tape, with tape still being lower.
You gotta first know what you are trying to do, THEN figure out where
your
bottlenecks are, THEN figure out what technology matches your need and
fits your budget.
Wanda (I think I'm done for the day now and I'm sure glad it's Friday)
Prather
________________________________
From: ADSM: Dist Stor Manager on behalf of Schneider, John
Sent: Fri 6/8/2007 1:00 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: How to Incorporate a CDL into TSM environment?
Greetings,
A lot of the chatter about VTL's being good or bad seems to stem
from which vendors you listen to, and what they are trying to sell you.
There are a lot of dogmatic statements made by people on both sides of
this issue, usually by people with no personal experience about what
they are talking about. Somebody has fed them a sales line and they
dutifully parrot it back.
EMC sold their CDL product for about two years before IBM
entered the market. During that time you would not believe how many
times I heard IBM pooh-pooh the CDL saying it wasn't a good fit for TSM,
didn't perform well, whatever they had to say to compete against it. I
even heard someone recently say it was against the law to use a CDL if
you used the IBM drivers to talk to it. Against what law exactly?
Then after two years IBM came out with their VTL the TS7510, and
almost immediately came out with a Redbook about it with a TSM chapter
explaining why the TS7510 was such a good fit for TSM! Huh? And not
because it was a better product than the EMC one, it was actually
slightly slower and only scaled to about a fourth the size of the
largest EMC VTL. The only difference is that now IBM had something in
the marketplace, and that changed everything.
As Wanda has said, a lot of the distinctions fall down to how
you use the VTL, and if your expectations are set correctly. It is easy
for a vendor presentation to promise the moon without qualifying it's
claims. A single-engine DL4100 from EMC can sustain a 1100MB/sec (3.7
TB per hour) write speed like they claim IF:
1) You are writing multiple simultaneous virtual tape streams (like 16
or more),
2) You balance the I/O across at least 4 FC streams coming in the VTL
engine,
3) You have at least 5 or more disk drawers to spread out the I/O load.
4) You are not compressing at the VTL engine. If you compress at the
VTL engine, your performance will drop off, perhaps as low as a third as
fast. This is because the compression is done in software. If you want
hardware compression, go with one of the DL6000 series that has an
optional hardware compression engine.
But the presentations only say 1100MB/sec performance, and so customers
install one, set up a single backup to a single virtual tape drive, and
when it pegs at ~100MB/sec they think they have been lied to.
The other complaint I hear a lot is the claim of 3:1 compression.
Almost every vendor puts that in their literature as if it is a solid
fact, and not a typical value. I had a customer once get so mad they
almost yanked the whole box out and made the vendor take it back because
they bought a 10TB VTL, which they sized on the assumption of 3:1
compression. Never mind that the compression they were getting on their
existing LTO tape library was on 1.2:1, they were told the VTL would do
3:1, so it should.
I had another customer almost throw out IBM because they bought 12 new
3592 tape drives, and they wouldn't perform anywhere near their rated
performance. Never mind the fact that data was coming in through a
single GigE connection, and the 12 tape drives had an aggregate
throughput rating at about times that.
Customers looking to purchase any tape or disk technology would be wise
to ask questions about how performance numbers were achieved, and look
at their own situation to see what results they should expect.
Best Regards,
John D. Schneider
Sr. System Administrator - Storage
Sisters of Mercy Health System
3637 South Geyer Road
St. Louis, MO. 63127
Email: schnjd AT stlo.mercy DOT net
Office: 314-364-3150, Cell: 314-486-2359
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Prather, Wanda
Sent: Friday, June 08, 2007 10:56 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] How to Incorporate a CDL into TSM environment?
...I understood restore performance suffered with a VTL - the way it has
been described to me is that, should a restore need to come from a
volume that has been destaged from disk to tape in the VTL, then a
restore of a single file from the volume would first have to wait for
the vtl to rebuild the tape on disk? Or have I got the wrong end of the
stick?
Um. Both.
Most VTL's are disk-only devices that emulate tape, and do not have the
staging issue you describe.
Many VTL's will make restores FASTER because the tape mount time goes
from potentially minutes to a second or less. (You also don't have to
worry about collocating data in a VTL, so your migration times are
generally faster as well.)
Now that goes with a caveat - you have to PIN YOUR VENDOR TO THE WALL
and get documentation about throughput rates. ALL VTL's work about the
same way, but they all have different hardware inside the box, so you
can get drastically different results. You can easily create a case
where restoring 1 VERY LARGE file will take longer on a slow VTL than
with fast tape (Say a TS1120, which run get more than 100MB/sec.)
It depends on
WHICH VTL you are talking about,
the speed of the disk in it,
the size of the cache in it
the speed of your SAN connection and/or HBAs
compared to which tape drive, and
whether you are talking about restoring lots of little files or a
few huge ones.
A VTS (don't they make this confusing?) is an IBM-only mixture of
disk/tape that emulates tape. It has to pull data off tape and stage it
back to disk before you can restore. Normally the VTS is used in a
mainframe environment.
IBM also makes VTLs, the TS7510 and TS7520, for use in open
environments. They are all disk.
This e-mail (including any attachments) is confidential and may be legally
privileged. If you are not an intended recipient or an authorized
representative of an intended recipient, you are prohibited from using, copying
or distributing the information in this e-mail or its attachments. If you have
received this e-mail in error, please notify the sender immediately by return
e-mail and delete all copies of this message and any attachments.
Thank you.
|
