B2D ever faster than LTO3?

[rpowell]

I know this topic has been discussed before here but does anyone know if  B2D would ever be faster than LTO 3? My superior sold a B2D solution because he thought it would be faster than the LTO Tape drive were using for disk to tape. I've already learened here that the RAID 5 array will have to go if we want to get above 300mb but will it ever reach the 1.3 to 2 gb we're seeing from the B2T we're seeing? 

The network is definitly not the problem since we are getting that speed doing the same backup jobs accross the network, directly to the tape instead of the disk.

[Francois_Steyl]

Hi.

A lot of B2D solutions are sold with the incorrect focus. LTO3 Tape is extremely fast, and would outrun most Disk architectures when in the correct setup.

What is the exact setup of the disk solution that was sold? Also what driver is in use for the Disk Array?

A B2D solution is great in many aspects, but should not just be sold with speed performance increase in mind. It forms part of a bigger backup solution, and really become beneficial when restoring or copying of backups to Tape.

Francois

[rpowell]

The configuration is an Intel 2U with an Intel S5000PAL MB, Xeon 5110 Proc., 2 GB memory.

Intel SRC28X SATA RAID controller with 128 MB memory, no battery backup so the cache is write thru, no read ahead and direct I/O. Stripe size is 64k

3 Seagate ST3750640AS SATA HDD in RAID 5.

LSI PCI-X Ulrta 320 controller connected to and external 1U HP Ultrium 3 SCSI tape drive.

The original idea was to backup the three servers across the network using B2D during the night, then copy to tape during the day. When the throughput on B2D was a dismal 250-300 mb, we backed up directly to tape across the network and got throughput of up to 2 gb.

In device mgr., the RAID driver is the Intel driver provided by LSI  and the array driver is Microsoft

[Peter_Burgess]

There's alot of variables there. Is the OS install on those three drives ? Are they 15k RPM or 10k RPM ?

I get well over 2GB/minute on B2D but that's on 4x15k SCSI U320 drives with write caching. Also the OS is running on a separate set of drives so there's no other activity on these drives than the backup. In addition that's a backup from the SQL agent pulling down about 20GB of databases.

Backing up the same set to tape results in about 3GB/minute so (without any extensive testing) that would tend to suggest that the bottleneck is the drives rather than anything else.

I maybe wrong but I was under the impression that SATA drives don't come close to SCSI in performance ?

Pete

[rpowell]

As far as spindle speed goes, yea, your drives are twice as fast. The SATA drives are 7500 rpm. SATA II spec otherwise is pretty good. Everything is shifting towards SAS now but there are no drives bigger than 300 GB availble and those drives are about $1k a piece

The O/S resides on the same drives and partition.

You mention your using  4 drives, what is your RAID configuration?

[Peter_Burgess]

It's 4 x 300GB drives in a RAID5 set, so t's a fair bet that it's not the RAID performance that's killing it at your end.

[rpowell]

Ok, yea when I called tech support they told me that the RAID 5 was causing the problem and to reconfigure it as a RAID 1.....and that may give us 750 mb throughput which still stinks Only problem is that we'd loose half our drive space.

I wish we had the time to bench test the solution before we deployed it but we rarely have that luxury.

[Peter_Burgess]

If you're really hellbent on doing the B2D with the server you have now, best bet is to pick up a decent SCSI Raid controller and a drive shelf. Something like an HP MSA30. Raid 5 is fine as long as there's enough drives and speed in the drives to support it. Like I said I have 4 drives in a Raid 5 config.

Other than that, congratulate your superior on understanding the why but not the how and remind him how, in the future, he should leave tech decisions to tech people :)

[rpowell]

Believe me, if I could do that I would.

Thanks though, you info and experience is much appreciated.

[CharlieASmith]

Completely agree a decent controller would be in order, but more specifically one with write caching. Alternatively buy a battery for your existing controller and enable write caching. On my test system in RAID10 (smartarray 5302) I still only get 600MB/min without write caching, turn this on and I get close to 2GB/min (large files/databases) which is LTO2 territory at least....

[rpowell]

Ok, we reconfigured the server: added two  80 Gb in RAID 1 and ghosted the O/S on to that. Then we added an additional 750 GB drive for a total of 4 drives in a RAID 10 for the B2D. Added a battery to the controller and turned "everything" on.

We got 2.7 GB per min. B2D SQL server. Still have to test the other two servers but hell, that's like a 2.3 Gb increase, not bad for common 7200 RPM drives....