Archive for the ‘Hardware’ Category

Jan 3

If you’ve been thinking of building yourself a dedicated storage server, this oakley sunglasses sale is a good time to do it. Prices are so low now that even a small home network can have a dedicated storage and backup server for not much money. SATA hard drives have large capacities and high speeds for low prices, and you don’t need the latest greatest quad-core processor or trainloads of RAM. The ultimate in flexibility and reliability combines Linux software RAID (Redundant Array of Inexpensive Disks) and LVM (Linux Volume Manager).

These are good times for hardware geeks of all kinds: prices are low and features abundant. Most motherboards include cheap oakleys sunglasses a feast of onboard controllers that used to require separate expansion cards: audio, video, RAID, Firewire, and Ethernet. Laptops and monitors come with integrated microphones and ray ban sale cameras. Hordes of USB 2.0 ports means easy connectivity for peripherals. Gigabit Ethernet? They’re practically giving it away.

The best part is it’s easier than ever to store, backup and retrieve your data. My personal favorite use for USB is connecting cheap oakleys external re-writable storage devices; everything from little thumb drives to big hard drives. These are absolutely great for inexpensive backups and wholesale nfl jersyes file transfers, and even my most relentlessly techno-gumby friends and relatives can copy files to a USB stick. I suffered during those awkward transition years when 3.5″ diskettes were too small and there was nothing comparable to replace them. Zip drives were too unreliable, and non-standard — can you read those disks now? CDRWs were funky — sometimes you could read them, sometimes not, and packet-writing never did work reliably on any platform. DVD-RWs offered bigger capacities, but hard drives oakley sunglasses cheap still outstripped them. Plus there were (and still are) too many competing DVD standards, and just like their CDRW cousins they are not reliable enough.

My favorite solution for large-capacity backups and storage is hard drives. Yes, I know that tape storage rivals hard disks for storage capacity, but I don’t like it. It’s cumbersome, expensive, and non-portable. Hard drives are fast, easy, inexpensive, and —best of all— very portable. equipo They are readable without any special software or hardware; just stuff a drive into any PC, or in an external USB or Firewire enclosure attached to a PC. It doesn’t even have to be a Linux PC as long as you have a Linux LiveCD or USB stick. You’ll be able to read nearly any filesystem, and Linux offers a number of good data-recovery utilities if you need them.

But as excellent as all of these are, there comes a time when they’re not quite adequate, and that’s when a dedicated storage server is the right tool for the job.

One word: uptime. RAID protects you from drive failures. When a drive fails— and it’s always “when”, not “if”— the remaining disks carry on until you replace the dead disk. But do not expect RAID to replace regular backups, because it doesn’t. There are many things that can wipe out a Fake Ray Bans RAID array: power surges, multiple drive failures, undiscovered drive failures, theft, and disk controller failures are just a few examples. You can’t read individual disks from a RAID array, except for RAID 1, so you have to rebuild the array to access your data. If too many drives fail, you won’t be able to recover anything.

A RAID array, no matter how many disks are in it, looks like a single logical storage drive to your system. There are wholesale jerseys china several different basic levels of RAID, from RAID 0 to RAID 6. They use mirroring, striping, or parity, and various combinations of these. These are the three that are most commonly used:

There are other basic RAID levels, and combinations of the various basic levels, and Google is full of information on those. We’re going ray ban sunglasses to stick with the basics here.

Ever cheap football jerseys cheap nfl jerseys since the vi vs. Emacs wars died of boredom it’s been difficult cheap jordans online to find good flamefests. Even software RAID vs. hardware RAID has become mundane. But it’s worth reviewing the merits of each, because this isn’t a case of one being clearly superior over the other, but deciding which one meets your needs best.

I wouldn’t even bother Cheap Jerseys From China with a PATA RAID controller; they’re more trouble than help. SATA is where it’s at these days. First the advantages of a good-quality SATA hardware controller:

The two disadvantages of good RAID controllers are cost Анализы and inflexibility. 3Ware controllers are first-rate, but not cheap. Hardware controllers are picky about what hard disks you can use, and the entire disk must belong to the array, unlike Linux software RAID which lets you select individual disk partitions. Recovery from a controller failure means you need the exactly correct new controller. Some admins think that using a hardware controller is riskier because it adds a point of failure.

Poor-quality hardware RAID A controllers are legion. Those onboard RAID controllers and low-end PCI controllers aren’t really hardware controllers at all; they do all their work in (usually crappy) software.

Linux software RAID has these advantages:

If I were running a super-important mission-critical server that had to be up all the time and no excuses, I’d use SCSI drives and controllers. For everything else, Linux RAID Ray Ban Outlet + SATA + LVM. Why do we want LVM? So we can resize Cheap Jerseys From China our storage volumes painlessly.

Watch Movie Online Logan (2017)

These are suggested methods to prevent distributed denial of service attacks.

  1. Use the ip verify unicast reverse-path interface command on the input interface on the router at the upstream end of the connection.

    This feature examines each packet received as input on that interface. If the source IP address does not have a route in the CEF tables that points back to the same interface on which the packet arrived, the router drops the packet.

    The effect of Unicast RPF is that zona it stops SMURF attacks (and other attacks that depend on source IP address spoofing) at the ISP’s POP (lease and dial-up). This protects your network and customers, Ray Ban sale as well as the rest of the Internet. To use unicast RPF, enable “CEF switching” or “CEF distributed switching” in the router. There is no need to configure the input interface for CEF switching. As long as CEF is running on the router, individual interfaces can be configured Cheap nfl Jerseys with other switching modes. RPF is an input side function that enabled on an interface or sub-interface and operates on packets received by the router.

    It is very important for CEF to be turned on in the router. RPF does not work without CEF. Unicast RPF is not supported in any 11.2 or 11.3 images. Unicast RPF is included in 12.0 on platforms that support CEF, wholesale nfl jerseys which includes the AS5800. Hence, unicast RFP can be configured on the PSTN/ISDN dial-up interfaces on the AS5800.

  2. Filter all RFC-1918 address space using Access Control Lists (ACLs).

    Refer to this example:

    access-list 101 deny ip Cheap Ray Ban Sunglasses any
    access-list 101 deny ip Fake Oakleys any
    access-list 101 deny Cheap nba Jerseys ip any
    access-list 101 permit ip any any
    interface xy
       ip access-group 101 in

    Another source of information about special use IPv4 address space that can be oakley outlet filtered is the (now expired) IETF draft ‘Documenting Special Use IPv4 Address Blocks that have cheap jordans online been registered with IANA .’

  3. Apply ingress and egress filtering using ACLs.

    Refer to this example:

         { ISP Core } -- ISP Edge Router -- Customer Edge Router -- { Customer network }

    The ISP edge router should only accept traffic with source addresses belonging to the customer network. The customer network should only accept traffic with source addresses other than the customer network block. This is a sample ACL for an ISP edge router:

    access-list 190 permit ip {customer network} {customer network mask} any 
    access-list 190 deny ip any any [log] 
    interface {ingress interface} {interface #} 
    	ip access-group 190 in

    This is a sample ACL for a customer edge router:

    access-list 187 deny ip {customer network} {customer network mask} any 
    access-list 187 permit ip any any 
    access-list 188 permit ip {customer network} {customer network cheap nba jerseys mask} any 
    access-list 188 deny ip any any 
    interface {egress interface} {interface #} 
    	ip access-group 187 in 
    	ip access-group 188 out

    If you are able to turn cheap jerseys wholesale on Cisco Express Forwarding (CEF), the length on the ACLs can be substantially reduced and thus increase performance by enabling unicast reverse path forwarding. In order to support unicast reverse path forwarding, you only need to be able to enable CEF on the router as a whole; the interface on which the feature is enabled does not need to be a CEF switched interface.

  4. Use CAR to rate limit ICMP packets.

    Refer to this example:

    interface xy 
     rate-limit output access-group 2020 3000000 512000 786000 conform-action 
    transmit exceed-action drop 
    access-list 2020 permit icmp any cheap nba jerseys any echo-reply
  5. Configure rate limiting for SYN packets.

    Refer to this example:

    access-list 152 permit tcp any host eq www 
    access-list 153 permit tcp any host eq www established 
    interface {int} 
    	rate-limit output access-group 153 45000000 Cheap Jordans 100000 100000 
    conform-action transmit exceed-action drop 
     	rate-limit output access-group 152 1000000 100000 100000 
    conform-action transmit exceed-action drop

    In the previous example, replace:

    Note that if you set the burst rate greater than 30%, many legitimate SYNs may be dropped. In order to get an idea vulputate of where to set the burst rate, use the show interfaces rate-limit command in order to display the conformed and exceeded rates for the interface. Your objective is to rate-limit the SYNs as little as necessary to get things working again.