Frequently Asked Questions

The following Frequently Asked Questions apply to all Quix VTL Express Systems.

Installation

What Rack position should I mount the system?

Generally the systems can be mounted at any height within a rack. However there are two details to consider: First it has been observed that the top positions in a rack can be rather warm, and can lead to earlier equipment failures due to higher temperature. The general rule is to mount devices with mechanisms (e.g. disk drives) lower in the rack, and keep e.g. switches and routers at the top (which have few moving parts). The second consideration is the humans who may have to exchange storage media (disk drives) on a regular basis: It can be convenient to mount the system at approx. 1m height for that purpose.

Configuration

The Express 4500 have four virtual tape drives: Is it possible to split the system so that there are two virtual medium changers, each with two virtual tape drives?

Yes: You need to connect two virtual tape drives to the second virtual medium changer, and on the back end of the medium changer you need to assign which slots you want to be operated by the second medium changer. In general these virtual devices are completely independent of each other, and you are free to "connect" the virtual devices the way you want. This includes e.g. connecting some virtual tape drives to a different Fibre Channel port (if available), or changing the sequence of ports attached to a medium changer.

I can not change settings via the web interface

The web interface is read-only. In order to make changes to the system, you need to log in using ssh, and navigate through the menus using the arrow keys. We believe the menu system is very easy to use, in particular it is not a "command line". Both the menu system and the web page update the data displayed every 1-2 seconds. The web page is merely a tool to get a quick view of what is going on: On a single page you see how many MB/s each virtual tape drive transfers, what disk drive serial numbers are in each slot, etc.

Can I log in more than once?

Yes. You can log in multiple times concurrently & make changes.

On the product page I read that some systems have been running without rebooting for over a year. Does this mean that the customer did no configuration change?

No, the customer changed the configuration while operating the system. The configuration can be changed on a "live" system. For example, if you have a virtual medium changer and two virtual tape drives running a backup, while the backup is running you can change configuration of the other virtual medium changer and other virtual tape drives, without any interruption. The system supports hot-plugging of physical disk drives, and similarily support changes in the internal configuration at runtime.

I understand that disk drives are handled 1:1 as virtual tape cartridges, so when I remove a disk from the system my backup software will see that a tape cartridge was removed from the medium changer. How do I identify a disk -- with regular tape cartridges I have bar codes.

The Quix virtual medium changer supports a virtual bar code reader, and the "bar codes" it reads are the serial number codes of the SATA disk drives. That way, if e.g. in Backup Exec you do an "Inventory" operation, you'll see the SATA serial number as identification. The disk drives carry the same SATA serial number on their tag, so the drives can be reliably identified by checking the printed serial number on them.

The system allows to send e-mail in case of a failure. Do you offer a gateway to SMS?

No, but the email contents & subject is designed so that you can send it to an SMS gateway on your own: The Subject line essentially contains all information you need (including system identification) and this is the text that gets forwarded as an SMS.
Also the system moderates the number of emails generated, and collects multiple events into a single email message when too many occur.

System Design

Is there any RAID for the backup drives?

No! The goal of the Quix VTL systems is to replace slow clunky tape drives. Like with tape media, the user needs to be able to remove a single medium from the backup system to e.g. move it to an off-site location. If RAID were used, the user would have to move entire sets of disk drives, which would be inconvenient and error prone. Tape drives themselves also don't do RAID... the idea here is that the user does a backup every day -- the redundancy is reached by frequently doing full backups.

For the same reasons, Quix recommends doing full backups instead of incremental backups. Doing full backups on a regular basis is simple, and keeping things simple gives you good protection in case at some point you really depend on a backup.

Do you do de-duplication?

We believe de-duplication, if it is appropriate to use, should be done by the backup application because it has knowledge about the files. Even though de-duplication is a great hype at the moment, we're cautious about it: De-duplication has an aspect of self-betrayal for example if a company has "many backups" as seen in Backup Exec, but then stores them on a de-dup appliance that de-duplicates the date (removes redundancy) and saves everything on single RAID set. If that RAID becomes inconsistent (and they do), then all backups are lost at once.

Instead of doing great de-dup tricks with the data, we at Quix believe we better bring you cost-effective data storage itself so that you can keep the redundacy in the data and don't have to resort to de-duplication. De-duplication has a valid case where you have many servers with near-identical data on them (e.g. the Windows directory) -- here deduplication can eliminate duplicated files within the same backup / same day.

Hardware

Disk Drives: In most applications, it is sufficient to use consumer-grade disk drives, i.e. the "24x7 RAID" class of SATA drives is not required. In most cases, the disk drives in the VTL Express systems remain idle during most of the day, in which case the system spins down the disk drives. Unless the spindown is disabled, and unless a backup is running 24hrs a day, the disk drives are used in a similar way as in regular desktop PCs.

Disk Drive failures or H/T Mismatch errors: The VTL Express systems transparently forward errors. We never hide an issue, nor do we replace unreadable data with zero-filled data. As a result, when a disk reports unreadable data, you'll find H/T errors in the VTL Express log, and your backup program will report a bad medium. This is the way it should be we believe. Note that uninitialized disks can also lead to H/T errors -- in that case you should first initialize the disk as a Quix VTL medium (after checking it is the right disk).

Quix-supplied Disk Drives: These disk drives come mounted in a tray, VTL-initialized, and tested. You can buy Quix-supplied drives or you can buy your own.

Fibre Channel

Which Fibre Channel Switch do I need?

You do not necessarily need a Fibre Channel Switch. If you have only one or two systems to be connected to the VTL Express system, you can 1:1 connect them using a fiber optical cable. Fibre Channel completely supports operation without a switch.

I do have a Fibre Channel switch, what should I be aware of?

As with all backup systems on a Fibre Channel SAN, it is important to prevent one system from disturbing the other. Typically, Windows-based systems will try to access all the possible resources on a SAN, causing serious conflicts. Also, updates in the SAN topology (i.e. if a cable is plugged in or removed) sends update messages (RSCNs) to all systems, and some systems interpret that as an error.

The golden rule to operate a SAN is to use "zones" i.e. to separate the systems so that they do not influence each other. This is done on the FC switch.

Additionally, the Quix VTL Express systems allow to configure a "hard revervation" for each device (LUN): That way, the device accepts commands only from the computer it has been assigned to. See the user manual for hard reservations.

What are Fibre Channel SRR's ?

SRRs are Session Retry Requests - this is a mechanism that allows Fibre Channel devices to do error recovery within a data transfer. It is optional, but the Quix VTL Express implement it, because backup tape applications tend to be intolerant to failed commands.

Technology

During startup we see kernel console output. Is this a linux system?

The Quix VTL Express systems use Linux as a boot-loader and as a menu front-end. The actual data processing happens outside linux in a dedicated, Quix-developed operating system. This includes all device drivers, which are Quix-written. That way we do have complete control of the hardware behaviour. The many diagnostic output details in the menu interface of the system are made possible that way.

I plugged an additional SATA / Fibre Channel / SAS card into the system, but it does not show. What is wrong?

The Quix VTL Express systems support only specific types of I/O controllers -- also see question before.